Cytokine-mediated growth hormone release from cultured ovine pituitary cells

Previous studies have demonstrated that intravenous lipopolysaccharide (LPS) will increase concentrations of growth hormone (GH). One possible explanation for this may reside in the response of the pituitary to specific cytokines. This study sought to determine the effects of recombinant bovine tumor necrosis factor alpha (TNF), recombinant ovine (ro) interleukin-1alpha (IL-1alpha), roIL-1beta, ro interleukin-2 (IL-2), and ro gamma-interferon (INT) on GH release from cultured sheep pituitary cells. Sheep were sacrificed and pituitary cells cultured in DMEM with 10% fetal bovine serum for 3 days. On day 4, cells were washed and serum-free DMEM added to cells. IL-1alpha and IL-1beta were used at 0.2, 2 and 20 ng/ml and the remaining cytokines at 2, 20 and 200 ng/ml. Neither IL-2 nor INT had effects on basal or on GH-releasing hormone (GRH)-stimulated GH release. TNF inhibited GRH-stimulated GH release (p < 0.05). Both IL-1alpha and IL-1beta stimulated GH release from cultured pituitary cells at all doses tested (p < 0.01). Neither IL-1alpha nor IL-1beta had an effect on GRH-stimulated GH release. IL-1 effects were inhibited by H-89 (p < 0.05; a protein kinase A inhibitor) and by nifedipine (p < 0.05; a calcium channel blocker). Both of these mechanisms are central signal transduction mechanisms mediating GRH-stimulated GH release. IL-1-stimulated GH release is partially inhibited (p < 0.05) by lipoxygenase pathway blockers. Phorbol myristate acetate downregulation of protein kinase C did not alter IL-1-stimulated GH release. IL-1beta increased the content of both GH and GH mRNA in cultured sheep pituitary cells. We conclude that IL-1 produces a strong stimulus to GH release, which is mediated by calcium entry and protein kinase A activation. IL-1 also activates lipoxygenase pathways. This latter pathway as well as calcium entry were shown to mediate LPS stimulation of GH release from cultured pituitary cells. The similarity between IL-1 and LPS signal transduction suggests that LPS may activate pituitary production of IL-1 to produce the stimulus to GH. The lack of inhibitory effects of INT, TNF and IL-2 as opposed to what is seen in the rat may suggest a partial mechanism to explain the different effects of LPS on GH release between sheep and that seen in cattle and rats.     

Somatostatin plays a dual, stimulatory/inhibitory role in the control of growth hormone secretion by two somatotrope subpopulations from porcine pituitary

Previous results from our laboratory demonstrated the existence of two subpopulations of porcine somatotropes of low- (LD) and high density (HD) that exhibit differences in ultrastructure and respond in an opposite manner to somatostatin (SRIF) in vitro. In LD cells, SRIF did not affect basal growth hormone (GH) release but partially blocked the stimulatory effect induced by GH-releasing factor (GRF). Conversely, SRIF paradoxically stimulated the secretory activity of HD somatotropes. Here, we have analysed in detail the basic parameters that characterize this differential response. To this end, the time- and dose-dependent effects of SRIF-14 were evaluated on separate monolayer cultures of both subpopulations. Likewise, the direct effect of the peptide on individual somatotropes from each subset was assessed by cell immunoblot assay. Finally, we compared the effects of SRIF-14 and SRIF-28 on cultures of LD and HD cells. SRIF-14 (10(-7) M) induced a rapid (30 min) and sustained (4 h) 2-fold increase in GH release from HD cells, whereas it did not affect GH secretion from LD somatotropes. Surprisingly, a low dose of SRIF (10(-15) M) stimulated GH release from both LD (154.1 +/- 8.2% of basal, P < 0.05) and HD (337.2 +/- 55.5% of basal, P < 0.05) subpopulations, even more effectively than higher doses of the peptide. Results from cell blotting showed that SRIF stimulatory effects were exerted directly upon individual somatotropes. Finally, SRIF-28 elicited similar responses to those observed for SRIF-14 in both somatotrope subpopulations, yet 10(-15) M SRIF-28 was less potent than the same dose of SRIF-14 in stimulating GH release from HD cells. Our present findings demonstrate that SRIF can function as a true GH-releasing factor in cultures of porcine pituitary cells by acting specifically and directly upon somatotropes. Furthermore, together with previous observations, these results strongly suggest that SRIF is not merely an inhibitor of GH release in pigs, but might play a dual modulatory role. Heterogeneity of the somatotrope population contributes greatly to this divergent effect of SRIF.     

Neuramide stimulates adrenocorticotropin but not prolactin release from rat pituitary

Neuramide (NMD), a substance found in crude preparations of porcine stomach extract, is a viral inhibitor that also has putative immunostimulatory effects. The effects of NMD on stress-hormone (ACTH and prolactin-PRL) release were assessed in in vivo and in vitro studies. In the former, blood levels of corticosterone and PRL were measured in NMD-treated male rats. In vitro experiments were performed to evaluate the effects of NMD and three of its fractions (obtained with high performance liquid chromatography) on ACTH and PRL release from perfused rat pituitary slices. NMD increased plasma corticosterone levels in vivo and produced dose-dependent increases in in vitro pituitary release of ACTH. No effects on PRL secretion were observed in vivo or in vitro. The stimulatory effects on ACTH release were caused by the NMD fraction with a molecular weight of > 5000 < 10000 Da.     

Thyroid hormone stimulates progesterone release from human luteal cells by generating a proteinaceous factor

Specifications are the regulatory and legal standards that a product must meet to be suitable for use in humans. Specifications evolve in parallel with drug development and are refined prior to marketing authorization and, in some cases, after marketing. Recent changes in regulatory procedures for biotechnology-derived protein products have placed much emphasis on the use of characterization and final product specifications to provide assurance of overall quality of these products. In addition, harmonized guidelines for the testing and specifications for biotechnology products have been developed through the International Conference on Harmonization process. The availability of sensitive, quantitative, and specific analytical methods for characterization has made this possible, thus providing regulatory flexibility in the development of biotechnology-derived protein products. Further refinement of these analytical tools will undoubtedly enhance this regulatory flexibility.     

Effects of large doses of estrogen on prolactin and growth hormone release

The effects of large doses of estrogen on prolactin (PRL) release were assessed. Circulating PRL levels in response to intravenous infusion of 17 beta-estradiol (E2), at a rate of 50 mug per hour for 4 hours, were studied in 10 subjects, and a chronic administration of ethinyl estradiol (EE) at a dose of 400 mug per day, for 1 week, was evaluated in five hypogonadal subjects. There was a significant depression of serum level of PRL during the E2 infusion and a significant increase in PRL release after discontinuation of the infusion. The chronic treatment of large doses of EE induced a more rapid (within 36 hours) and a significantly greater elevation of PRL levels at the end of 1 week treatment than those found during smaller doses of EE administration, as reported previously. These data suggest that acute treatment of estrogen may have a biphasic action on the pituitary PRL section and that the augmentatory effect of estrogen on PRL secretion is dose-dependent in human beings.     

Serotonin directly stimulates luteinizing hormone-releasing hormone release from GT1 cells via 5-HT7 receptors

Effects of brief treatment of growth factors on the urogenital sinus of embryonic rats were investigated and it was found that 8 hour-treatment in the beginning of 5-day cultivation with the epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) can provoke prostatic bud formation, in the medium deprived of androgens.     

Differential sensitivity of prolactin release to dopamine and thyrotrophin-releasing hormone in intact and pituitary stalk-sectioned rhesus monkeys

The effects of dopamine and thyrotrophin-releasing hormone (TRH) on prolactin release was studied in 14 intact and six pituitary stalk-sectioned (SS) female rhesus monkeys (Macaca mulatta). Baseline prolactin values were ninefold higher in SS animals (149+/-16 ng/ml) than in intact animals (16+/-1 ng/ml). Prolactin release after intravenous administration of TRH in doses of 0, 125, 250, 500 and 1000 ng revealed that SS monkeys were more sensitive to the prolactin-releasing activity of this tripeptide than were intact animals. A significant (P less than 0.05) increment in serum prolactin was observed in SS animals after injection of 125 ng TRH whereas 250 ng was required to raise prolactin levels in the circulation of intact animals significantly (P less than 0.05). Furthermore, at each comparable dose level of TRH, the increment in serum prolactin was distinctly greater in SS animals than in intact monkeys. Infusion of dopamine at the rate of 10 microgram/kg body weight per min significantly (P less than 0.05) lowered prolactin levels within 60 min in intact animals and no further decline was observed with 20 or 40 microgram dopamine. Serum prolactin concentrations were not affected by saline infusion or by 5 microgram dopamine. Infusion of dopamine at the rate of 10 microgram/kg body wt per min also resulted in significant (P less than 0.01) suppression of serum prolactin in SS animals. This prolactin decrease was apparent within 40 min. Prolactin release after 500 ng TRH was less in these dopamine-treated SS monkeys than after an infusion of saline. Higher doses of dopamine (20 and 40 microgram) did not cause a further decrease in basal serum prolactin concentrations, but these two dopamine treatments blocked the increase in prolactin elicited by 500 ng TRH. The results suggest that the removal of hypothalamic influence, possibly related to the effects of dopamine, renders the pituitary gland more sensitive to the prolactin-releasing action of TRH.     

Effect of 17beta-estradiol on somatostatin receptor expression and inhibitory effects on growth hormone and prolactin release in rat pituitary cell cultures

Predictions of the minimal size an organism must have to swim along stimulus gradients were used to compare the relative advantages of sensory systems employing spatial (simultaneous) and temporal (sequential) gradient detection mechanisms for small free-swimming bacteria, leading to the following conclusions: 1) there are environmental conditions where spatial detection mechanisms can function for smaller organisms than can temporal mechanisms, 2) temporal mechanisms are superior (have a smaller size limit) for the difficult conditions of low concentration and shallow gradients, but 3) observed bacterial chemotaxis occurs mostly under conditions where spatial mechanisms have a smaller size limit, and 4) relevant conditions in the natural environment favor temporal mechanisms in some cases and spatial mechanisms in others. Thus, sensory ecology considerations do not preclude free-swimming bacteria from employing spatial detection mechanisms, as has been thought, and microbiologists should be on the lookout for them. If spatial mechanisms do not occur, the explanation should be sought elsewhere.     

Neuropeptide-Y stimulates growth hormone and gonadotropin-II secretion in the goldfish pituitary: involvement of both presynaptic and pituitary cell actions

We have previously reported that neuropeptide-Y (NPY) stimulates GH and gonadotropin-II (GtH-II) release from perifused pituitary fragments in the goldfish. Since the teleost pituitary is directly innervated by neurosecretory terminals from the brain, we further investigated the possible sites of action of NPY. Both synthetic human NPY and NPY-(18-36), an agonist selective for the NPY Y2-receptor, stimulated GH and GtH-II release from the pituitary fragments; the magnitude of the response to NPY (18-36) was smaller than that to the whole molecule of NPY. NPY also stimulated the release of GH and GtH-II from perifused dispersed pituitary cells. In contrast, NPY-(18-36) had no effect on either GH or GtH-II release from dispersed pituitary cells. These data suggest that Y2 action is not direct at the level of pituitary cells, but may be indirect through actions on nerve terminals in the pituitary. The hypothesis that the action of NPY on GH and GtH-II release is mediated in part by GnRH was then tested. Both NPY and NPY-(18-36) stimulated the GnRH release from preoptic-anterior hypothalamic slices and pituitary fragments with similar potency. Furthermore, a GnRH antagonist significantly reduced the effects of NPY on both GH and GtH-II release in perifused pituitary fragments. Similar to previous findings, NPY, when given at 55-min intervals, desensitized the hormone responses in pituitary fragments. Similarly, the same treatment with NPY in perifused dispersed pituitary cells induced desensitization of GH and GtH-II responses. Together, these results suggest that 1) more than one type of NPY receptors are present in the goldfish pituitary; and 2) NPY has at least two sites of action in the pituitary. One site of action is the pituitary cells, where NPY directly stimulates GH and GtH-II secretion; the second is the nerve terminals, where NPY presynaptically stimulates GnRH release via Y2-like receptors, and GnRH, in turn, stimulates GH and GtH-II release.     

Enhancement of secretagogue-induced adrenocorticotropic hormone release from cultured sheep anterior pituitary cells by recombinant ovine interleukin 1

Interaction between protein disulfide isomerase, possessing not only isomerase but also chaperone-like activity, and olygomeric enzyme, GAPDH, has been studied using technique of immobilization on insoluble support. PDI dimers bound to CNBr-activated Sepharose were shown to possess high TPOR activity as well as the ability to reactivate lysozyme. Immobilized PDI was not found to interact neither with soluble tetrameric GAPDH, nor with soluble denatured GAPDH. However, soluble PDI binds effectively to immobilized GAPDH monomers; Kd was found to be 3.7 x 10(-6) M, stoichiometry 0.824 mole PDI monomers per mole GAPDH monomers. Immobilized GAPDH tetramers do not interact with PDI. These observations are also confirmed by the data on electrophoresis of proteins bound to immobilized GAPDH monomers and tetramers. The ability of PDI to interact with denatured protein form, but not with the native one, is considered to be evidence of chaperone-like activity of the enzyme.     

Bombesin regulation of adrenocorticotropin release from ovine anterior pituitary cells

Mammalian members of the bombesin-like peptide family (gastrin releasing peptides; GRP) have been localized in the ovine median eminence and in hypophysial-portal blood, suggesting a role in the regulation of anterior pituitary function. In this study we have shown that although bombesin cannot stimulate ACTH secretion alone, it potentiates release by ovine CRF, an effect blocked by the GRP receptor antagonist D-Tyr6bombesin (6-13) propylamide. Bombesin did not potentiate AVP-stimulated ACTH release; instead release was attenuated when bombesin was given at a 10-fold or greater molar excess over AVP, with no interaction seen at lower concentrations. We conclude that ovine corticotrophs express bombesin receptors, and that GRP may act in concert with other hypothalamic releasing factors to regulate ACTH secretion.     

Influence of exogenous porcine growth hormone on vitamin D metabolism and calcium and phosphorus absorption in intact pigs

The influence of growth hormone (GH) on vitamin D metabolism and calcium and phosphorus absorption in vivo is not clear. We, therefore, measured calcium and phosphorus balance, plasma 1,25-dihydroxyvitamin D (1,25(OH)2D), and intestinal vitamin D-dependent calcium-binding protein (CaBP 9k) in intact growing pigs given exogenous GH. Six 10-week-old pigs were given two daily subcutaneous injections of 50 micrograms porcine GH/kg body weight for 2 months; six control pigs were given vehicle. They were all fed a diet containing 1.1% Ca, 0.6% P, and 1000 IU vitamin D3/kg. Apparent Ca and P absorption and retention were measured in a 10-day balance trial at the end of the 2 months. The plasma levels of Ca, P, 1,25(OH)2D, IGF-I, and GH were determined, and the duodenal and jejunal mucosal CaBP 9k content was measured at slaughter. The plasma Ca and P of GH-treated pigs were unchanged, but all aspects of mineral metabolism, including the plasma 1,25(OH)2D concentration (40%), Ca absorption and retention (70%), P absorption (33%) and retention (45%), and jejunal CaBP 9k (40%), were stimulated, in addition to an increase in the circulating IGF-I concentration.     

Effects of divalent cations and of a calcimimetic on adrenocorticotropic hormone release in pituitary tumor cells

The calcium sensing receptor (CaSR), a member of the G-protein coupled receptor family, is expressed on a variety of cell types and responds to extracellular calcium. We have characterized pharmacological properties of (+/-)NPS 568, a calcimimetic, toward cloned rat brain extracellular Ca2+-sensing receptor (CaSR) expressed in Chinese hamster ovary (CHO) cells and constitutive mouse CaSR in AtT-20 cells. In the presence of 1.3 mM Ca2+, the calcimimetic displayed a potency in the micromolar range in augmenting the inositol phosphates (IP) response in both cell lines and behaved as a full agonist. (+/-)NPS 568 stimulated formation of arachidonic acid release in CHO(CaSR) with a similar potency. The IP dose response curves of (+/-)NPS 568 were shifted to the left in the presence of increasing Ca2+, indicating that the potency of the drug is dependent on extracellular Ca2+ in both cells. In AtT-20 cells, Ca2+ and Ba2+, two CaSR agonists, induced a potent stimulation of adrenocorticotropic hormone (ACTH) secretion. In the presence of 1.8 mM Ca2+, (+/-)NPS 568 led to a dose dependent secretion of ACTH with an EC50 of 0.3 microM and a maximal effect comparable to Ca2+. The similar potency of the calcimimetic on IP and ACTH responses and the sensitivity of these responses to extracellular Ca2+ indicate that the Ca2+-sensing receptor expressed in AtT-20 cells is implicated in ACTH release. These data further characterize the pharmacology of the Ca2+-sensing receptor and argue for a role for extracellular Ca2+ and CaSRs in controlling ACTH secretion, a hormone implicated in several types of stress.     

Effects of interleukins on secretion of luteinizing hormone from ovine pituitary cells

OBJECTIVE: To determine whether cytokines of homologous species might mediate the stimulatory effects of endotoxin on release of luteinizing hormone (LH) from pituitary cells. SAMPLE POPULATION: Cells from pituitary glands collected from 8- to 14-month-old wethers. PROCEDURE: Cells from the anterior pituitary gland were cultured in the presence of recombinant ovine or bovine cytokines (interleukin [IL]-1alpha, IL-1beta, and IL-2), tumor necrosis factor-alpha (TNF), and interferon-gamma (IFN-gamma). Luteinizing hormone that was released into the medium was measured. Cells were also cultured with modulators of signal transduction pathways to evaluate the second messenger system used by IL-1 alpha and IL-1beta. RESULTS: Similar to effects of endotoxin, IL-1alpha and IL-1beta stimulated release of LH. Interleukin 2, TNF, and IFN-gamma did not have a detectable effect on release of LH. Stimulation of LH release by IL-1alpha and IL-1beta required activation of voltage-dependent Ca2+ channels and appeared to involve protein kinase C. CONCLUSIONS: IL-1alpha and IL-1beta may mediate the direct stimulatory effect of endotoxin on release of LH in vitro. Interleukin 2, TNF, and IFN-gamma do not have a direct effect on release of LH; therefore, they do not mediate this effect of endotoxin. CLINICAL RELEVANCE: Stressors, including infection, are often associated with reduced fertility. Infection resulting in endotoxin release, production of interleukins, or both, can lead to direct stimulation of LH release from the pituitary gland. Inopportune release of LH via cytokines may interfere with normal pulsatile release of LH, thereby suppressing gonadal function.     

Caffeine stimulates amyloid beta-peptide release from beta-amyloid precursor protein-transfected HEK293 cells

Extracellular amyloid beta-peptide (A beta) deposition is a pathological feature of Alzheimer's disease and the aging brain. Intracellular A beta accumulation is observed in the human muscle disease, inclusion body myositis. A beta has been reported to be toxic to neurons through disruption of normal calcium homeostasis. The pathogenic role of A beta in inclusion body myositis is not as clear. Elevation of intracellular calcium following application of calcium ionophore increases the generation of A beta from its precursor protein (betaAPP). A receptor-based mechanism for the increase in A beta production has not been reported to our knowledge. Here, we use caffeine to stimulate ryanodine receptor (RYR)-regulated intracellular calcium release channels and show that internal calcium stores also participate in the genesis of A beta. In cultured HEK293 cells transfected with betaAPP cDNA, caffeine (5-10 mM) significantly increased the release of A beta fourfold compared with control. These actions of caffeine were saturable, modulated by ryanodine, and inhibited by the RYR antagonists ruthenium red and procaine. The calcium reuptake inhibitors thapsigargin and cyclopiazonic acid potentiated caffeine-stimulated A beta release. NH4Cl and monensin, agents that alter acidic gradients in intracellular vesicles, abolished both the caffeine and ionophore effects. Immunocytochemical studies showed some correspondence between the distribution patterns of RYR and cellular betaAPP immunoreactivities. The relevance of these findings to Alzheimer's disease and inclusion body myositis is discussed.     

Platelet-derived growth factor stimulates the release of protein kinase A from the cell membrane

The mitogenic action of growth factors involves the stimulation of intracellular protein kinases. In this report we have characterized the major protein kinase released from Balb/c 3T3 and normal rat kidney plasma membranes by the action of platelet-derived growth factor (PDGF). PDGF appears to stimulate the release of approximately 10 proteins, at least one of which is a kinase capable of phosphorylating proteins on Ser or Thr (as determined by the lability of the phosphate to alkali treatment). More than 90% of the Ser/Thr kinase activity was inhibited by PKI5-22, a specific peptide inhibitor of the cAMP-dependent protein kinase (PKA). We used immunoblotting to confirm that the kinase released in response to PDGF was PKA. cAMP also stimulated the release of PKA, and the set of protein substrates phosphorylated was similar following PDGF or cAMP stimulation. Interestingly, in the presence of a cAMP analogue ((Rp)-cAMPS), cAMP could not induce dissociation of PKA from the membranes, whereas stimulation by PDGF increased the level of PKA activation. Furthermore, unlike Swiss 3T3 cells, neither Balb/c 3T3 fibroblasts nor normal rat kidney cells accumulate cAMP in response to PDGF, yet the level of PKA in the cytosol of these intact cells increases in response to PDGF. Thus, it appears as though PDGF activation of the membrane-associated form of the PKA holoenzyme occurs by a mechanism independent of an elevation in cAMP levels.     

Phenomenon of intrinsic rhythm of luteinizing hormone release from isolated anterior pituitary gland of female rat

The intrinsic nature of rthymic release of luteinizing hormone (LH) of isolated human and rat anterior pituitary gland reported independently by Macro Gambacciani and Xie in 1987 can be more directly demonstrated by a computer programme of Time Series-HSY Hidden Periodic Analytic Approach for continuous monitoring the LH output of the perfusate from a perfusion system with in vitro anterior pituitary of SD female rat. The results are as follows: (1) Under various reproductive conditions the average frequency (min/cycle) and amplitude (ng/ml) of the intrinsic rhythm of LH release were quite different: In proestrous group the frequency and amplitude were the highest, being intermediate in the ovariectomized group and lowest in the lactation group. (2) The intrinsic rhythm of LH release could be changed by either peptide or steroid hormones. In proestrous group with 30 min of gonadotropin-releasing hormone (GnRH), stimulation would reduce both frequency and amplitude. In case of lactation, the frequency was unchanged, but amplitude lowered, while in the ovariectomized rat pituitary, the 30 min GnRH stimulation decreased the frequency of release only. The intrinsic rhythm of the LH release could also be influenced by steriod hormones (Ru486 and Anordrin). With 120 min before removal of the anterior pituitary gland the rats receiving i.m. injection of Ru486 (2 mg/kg bw) or Anordrin (2 mg/kg), the results showed that Ru486 decreased frequency, while Anordrin decreased only the frequency to a less extent, both without amplitude affected. (3) Verapamil and EGTA added to the perfusion system did not abolish but only decreased the rhythmic phenomenon by using proestrous pitutary. This suggests that participation of Ca2+ may take place in the intrinsic release of LH. The above results indicated that the intrinsic rhythm of LH release of isolated anterior pituitary gland is different from various reproductive hormonal conditions and capable of being modified by exogenous hormones. The physiological function of the intrinsic rhythm of LH release of anterior pituitary gland remains to be elucidated.     

Thyroid hormone inhibits growth and stimulates terminal differentiation of epiphyseal growth plate chondrocytes

As a continuation of our studies on mineralization in epiphyseal growth plate (GP) chondrocyte cultures, the effects of tri-iodothyronine (T3) in both beta-glycerophosphate-containing, serum-free (HL-1) and beta-glycerophosphate-free, serum-containing medium (DATP5) were studied. The GP cells responded to T3 in a serum-, stage-, and dosage-dependent manner. Added at graded levels (0.1-10.0 nM) to preconfluent cultures (from day 7) in both HL-1 and DATP5, T3 caused progressive decreases in protein, collagen, and DNA synthesis but increased mineral deposition. In postconfluent cultures, these effects of T3 were generally muted. In preconfluent cultures, proteoglycan (PG) levels were not significantly affected in DATP5, although in HL-1 they were decreased by approximately 50%. In postconfluent cultures, T3 increased PG levels in DATP5 but had no effect in HL-1. In HL-1, alkaline phosphatase (ALP) activity was progressively increased by 200-500% in both pre- and postconfluent cultures. In DATP5 in preconfluent cultures, T3 initially stimulated but later suppressed ALP; in postconfluent cultures, T3 also transiently increased ALP but did not suppress activity upon longer exposure. The inhibitory effects of T3 on protein, PG, and DNA levels of GP chondrocytes suggest that in vivo its effects on bone growth must occur primarily after cellular proliferation. Apparently by binding to the 50 kDa thyroxine-binding globulin, which cannot penetrate the PG barrier, accessibility of T3 to GP chondrocytes is limited until the time of vascular penetration when its stimulatory effects on ALP and mineral deposition become critical for continued bone development.     

Stimulation by urocortin of growth hormone (GH) secretion in GH-producing human pituitary adenoma cells

Urocortin (Ucn) possesses high homology with CRH and is considered to be a ligand to type-2 CRH receptor. We investigated the effect of Ucn on hormone release from cultured GH-producing human pituitary adenoma cells in vitro. GH-producing human pituitary adenoma cells were superfused on a Sephadex G-25 column. Both Ucn (10 nM) and CRH (10 nM) elicited an increase in GH release from the pituitary adenoma cells in one patient with acromegaly. In contrast, GH release from the pituitary adenoma cells was stimulated by Ucn but not by CRH in the other patient with acromegaly. These preliminary findings suggest that type-2 CRH receptors are expressed in some population of GH-producing human pituitary adenoma cells and that Ucn might be involved in GH secretion from tumorous tissues in patients with acromegaly.     

Influence of serum, estrogen, and gonadotropins upon growth and progesterone secretion by cultures of granulosa cells from small porcine follicles

Granulosa cells from small (less than 2mm) antral porcine follicles were grown in culture to study the effects of various hormones on growth, morphology and progesterone secretion. Culture medium 199D + 4% serum was found to be most suitable since it maintained a fairly constant cell population. Estradiol (1mug/ml) and human FSH stimulated cell growth. LH and FSH stimulated progesterone secretion and induced morphological changes associated with luteinization. Estradiol (0.1 mug/ml) inhibited progesterone secretion by granulosa cells.