Daily variations of platelet aggregation in relation to blood and plasma serotonin in diabetes

INTRODUCTION: An increase in digitalis-like substances has been reported in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We hypothesized that the role of saline and unilateral nephrectomy in DOCA hypertension may be due to stimulation of endogenous digitalis-like substances. METHODS: We investigated the effects of digoxin and DOCA alone and in combination in intact rats drinking water. Forty male Sprague-Dawley rats were used (body weight 223-298 g). RESULTS: Neither digoxin (40 micrograms/kg per day, by gavage, for 35 days, n = 10) nor DOCA (30 mg/kg twice a week, subcutaneously, for 5 weeks, n = 10) caused a consistent increase in blood pressure in intact rats drinking water. In contrast, combined digoxin and DOCA administration (n = 10) increased systolic blood pressure from day 18 of treatment onwards, to a maximum at day 34 compared with sham-treated rats (n = 10). There were no consistent changes in water intake, urine volume, urinary sodium or potassium excretion, or plasma sodium or potassium concentration with digoxin treatment. DOCA increased water intake and urine volume, and caused an initial decrease in urinary sodium excretion, but no change in urinary potassium excretion or plasma sodium concentration. Plasma potassium excretion was lower in DOCA- than sham-treated rats. CONCLUSION: Combined digoxin and DOCA administration in intact rats drinking water increased blood pressure significantly compared with either drug alone, raising the possibility that the mechanism by which nephrectomy and salt loading contribute to DOCA hypertension in the rat might be through stimulation of endogenous digitalis-like substances.     

Electron-microscopic morphometric analysis of mouse liver. I. Experimental studies on the morphogenetic significance of the thymus in nude and normal mice

Haired, nude, thymus-grafted nude and haired thymectomized Balb/c-nu mice 2 months of age were studied by electron-microscopic stereology. Each group consisted of 5 animals and a complete morphometric analysis was carried out on their livers. In the absence of the thymus there is a slowing down of the development of the whole organism. Among the liver parameters especially the nuclear ones displayed alterations. Namely, the volume of hepatocyte nuclei increased above the normal level and this phenomenon was reversed by thymus graft into the nude mice. The hepatocyte volume also increased significantly in the surgically thymectomized group, influencing all the morphometric parameters regarding mitochondria and endoplasmic reticulum, when measured per hepatocyte. On the basis of the results obtained, one can conclude that the thymus has a regulatory role in the development of hepatocyte morphology. The findings agree with the biochemical observations demonstrating non-immunological effects of the thymus on cellular development.     

Does the Sabra hypertension-prone rat represent a model of salt or mineralocorticoid sensitivity?

OBJECTIVES: Since the Sabra experimental model of hypertension was developed, it has been known as a model of salt-susceptible hypertension. Because the hypertensive response of the Sabra hypertension-prone strain (SBH/y) is classically elicited by salt loading with a combination of deoxycorticosterone acetate (DOCA) and salt, doubt has now been cast on whether the hypertensive response is due to sensitivity to salt or to mineralocorticoids. The present study was designed to resolve this question. MATERIALS AND METHODS: We studied the blood pressure response of SBH/y to various modes of salt loading. Animals were salt-loaded by administration of: 1% NaCl in drinking water and subcutaneous implantation of a 25 mg DOCA pellet (DOCA-salt); DOCA alone; 1% NaCl in drinking water alone; or 8% NaCl in chow alone. Blood pressure was determined by the tail-cuff method in awake and undisturbed animals. RESULTS: Within 4 weeks, the DOCA-salt treatment elicited the full hypertensive response previously reported in the SBH/y strain. Salt loading with 8% NaCl in chow reproduced the full hypertensive response observed with DOCA-salt, except that it occurred only after 7 weeks of treatment. Salt loading with DOCA alone raised blood pressure moderately and to a maximal level within 3 weeks; the magnitude of the blood pressure response was, however, significantly smaller than that observed with DOCA-salt or 8% NaCl in chow. Administration of 1% NaCl in water alone elicited no hypertensive response. CONCLUSIONS: The hypertensive response to salt loading in the Sabra experimental model of hypertension is an expression primarily of salt sensitivity, as it can be fully reproduced with salt alone, but not with DOCA alone. The use of the DOCA-salt mode of salt loading in this model, as opposed to salt loading with 8% salt in chow, is a useful way of accelerating the development of salt-sensitive hypertension in SBH/y, which shortens, and therefore facilitates, phenotyping.     

Induction of IgG in young nude mice by lipid A or thymus grafts

Postnatal serum concentrations of IgG2a of paternal allotype, measured in congenitally thymusless nude mice, increase with kinetics and titers comparable to their normal congeneic counterparts. Lipid A, the mitogenic part of LPS, stimulates IgG synthesis in nude mice when it is given 7 days after birth. IgG concentrations at 15 days of age are 6- to 8-fold higher than in untreated control nudes; this is considerably lower, however, than in normal mice, which show up to 45-fold higher IgG2ab levels after lipid A treatment. A thymus graft from nearly congeneic donors of the same age, transplanted at 4 days after birth, also stimulates long-lasting IgG synthesis in the nude recipients. If the grafted nudes are injected with lipid A 3 days later, IgG synthesis is further stimulated 8- to 16-fold. The data are discussed in relation to the thymus dependency of IgG production and the conditions for lipid A stimulation.     

Integrated cardiovascular function in the conscious streptozotocin-diabetic deoxycorticosterone-acetate-hypertensive rats

Blood pressure, heart rate, and left ventricular function were measured in conscious diabetic Sprague-Dawley rats subjected to 5 weeks of deoxycorticosterone acetate (DOCA) treatment which was started 1 week following intravenous injection of streptozotocin (STZ) (60 mg/kg) to induce diabetes mellitus. It was found that chronic administration of DOCA in nondiabetic animals caused an increase in blood pressure and functional parameters of left ventricle, and a decrease in heart rate and plasma insulin levels. Normotensive diabetic rats exhibited hyperglycemia, hypoinsulinemia, and a lower body weight as compared with control animals but did not show significant abnormalities in cardiovascular function. DOCA-hypertensive STZ-diabetic rats had similar hyperglycemia, milder hypoinsulinemia, and a significantly lower rate of left ventricular relaxation and systolic blood pressure compared with the nondiabetic DOCA-hypertensive animals. It is concluded that the addition of DOCA hypertension to intact 6-week STZ-diabetic Sprague-Dawley rats results in the occurrence of cardiac dysfunction.     

Induction of diverse arterial and myocardial lesions by adrenal regeneration hypertension in Sprague-Dawley versus spontaneously hypertensive rats

Nonarteriosclerotic, virgin, Sprague-Dawley (SD), and spontaneously hypertensive (SHR) rats and arterio sclerotic breeder SD and SHR rats were subjected to adrenal regeneration-induced hypertension (ARH) with and without extra salt. ARH caused a marked increase in the blood pressure of SD rats and a mild increase in SHR rats; extra salt caused exacerbation of hypertension in SD rats only. Heart and kidney weights were greatly increased commensurate with blood pressure. Increased adrenal weight concomitant with thymus gland involution was considerable in SD and less marked in SHR rats. Testes and ovaries were involuted. Creatine phosphokinase and lactic dehydrogenase levels were abnormally high; blood triglycerides, FFA, glucose, and corticosterone decreased, and total cholesterol, glucose, and corticosterone increased in SD but decreased in SHR rats. Blood urea nitrogen levels were much more abnormally elevated in SD than in SHR rats. ARH did not induce arterial disease in the virgin SD or SHR rats, but it did produce a spectrum of arterial disease in SH breeders, e.g. aortic sclerosis, polyarteritis nodosa-like lesions, intimal cartilaginous metaplasia, and hyalin fibrosis. Altered adrenocortical steroidogenesis may have conditioned the arterial wall of SHR rats to develop diverse morphological changes, and extra salt is much more detrimental to normotensive rats (SD) than to genetically hypertensive rats.     

Endotoxin-induced size change in bone marrow progenitors of granulocytes and macrophages

Injection of 5 mug endotoxin to adult C57BL mice caused a marked increase in the sedimentation velocity of granulocytic and macrophage progenitor (colony-forming) cells in the bone marrow. This change was maximal two days after injection and was not accompanied by corresponding changes in total marrow nucleated cell populations. The endotoxin-induced shift was not dependent on the presence of the thymus but did not occur in mice challenged after preinjection with endotoxin. No changes in buoyant density, cell cycle status, pattern of differentiation and responsiveness of granulocytic and macrophage progenitor cells were observed after the injection of endotoxin. The increased sedimentation velocity of progenitor cells appears to indicate an increase in cell volume but the mechanisms involved have not been identified.     

In vitro suppression of macrophage spreading caused by supernatants of tumour, thymus, and lymph node cells

Peritoneal macrophages washed out from C3Hf/Bu mice were cultivated in medium 199 supplemented with 35% foetal calf serum. If the pH of the medium was adjusted to 7.2, there were 70% spread macrophages after six hours of incubation at 37 degrees C. We investigated the effect of tumour cells on macrophage spreading. Supernatants from cell cultures of a fibro-sarcoma of C57BL mice and lymphoma of C3Hf/Bu mice were used to determine the number of spread macrophages after 6 hours of culture in these supernatants. Supernatants from cell cultures of the kidney, thymus and lymph nodes of normal C57BL or C3Hf/Bu mice and peritoneal cells of normal C3Hf/Bu mice in medium 199 alone served as control. We observed that supernatants from both allogeneic and syngeneic tumour cell cultures reduced significantly the percentage of spread macrophages in comparison with the percentage of spread macrophages found in the kidney culture supernatants. However, a similar spreading inhibition was caused also by supernatants from the thymus and lymph node cell cultures. In these experiments we confirmed the earlier observations that tumour cells can suppress the activation of macrophages, and we also pointed to the possibility that this effect is not specific only for malignant tissues.     

Renal afferent impulses, the posterior hypothalamus, and hypertension in rats with chronic renal failure

Hypertension in 5/6 nephrectomized (CRF) rats is partly related to increased activity of the sympathetic nervous system. We have previously shown a greater norepinephrine turnover rate in the posterior hypothalamic nuclei and locus coeruleus of CRF than control rats. Dorsal rhizotomy prevented the rise in blood pressure and the increase in NE turnover rate in the posterior hypothalamus and the locus coeruleus. The studies suggest that afferent impulses from the kidney to central integrative structures in the brain may be responsible for hypertension in CRF rats. To further evaluate the role of renal afferent nerves in the regulation of blood pressure, and whether renal afferent pathways integrate with the posterior hypothalamus, we studied the effects of an intrarenal injection of 50 microliters of 10% phenol on blood pressure and NE secretion from the posterior hypothalamus of Sprague-Dawley rats. Mean arterial pressure increased from 89 +/- 4.0 to 114 +/- 4.3 mm Hg in rats which received intrarenal injection of phenol, but it did not change in rats that received vehicle (95 +/- 4.3 and 89 +/- 3.6 mm Hg, respectively). Renal denervation totally prevented the increase in blood pressure caused by intrarenal injection of phenol. The secretion of NE from the posterior hypothalamus increased from 139 +/- 4.8 to 250 +/- 9.9 pg/ml (P < 0.01) in rats that received intrarenal phenol, but it did not change in rats which received vehicle or in those with renal denervation. In CRF rats NE secretion from the posterior hypothalamus was greater than in control and CRF rats subjected to dorsal rhizotomy. These studies show that afferent impulses from an injured kidney increase NE secretion from the posterior hypothalamus and raise blood pressure. NE secretion is higher in the posterior hypothalamus of CRF than control rats. The posterior hypothalamus appears to be an important integrative structure of the sympathetic regulation of blood pressure.     

A proteasome inhibitor lessens the increased aortic endothelin-1 content in deoxycorticosterone acetate-salt hypertensive rats

Deoxycorticosterone acetate (DOCA)-salt-treated rats developed marked hypertension after 4 weeks with an increase in aortic endothelin-1. Treatment of DOCA-salt hypertensive rats with a proteasome inhibitor, N-benzyloxycarbonyl-Ile-Glu(O-t-Bu)-Ala-leucinal, significantly reduced the elevation in systolic blood pressure and the effect was accompanied by a decrease in aortic endothelin- content. Thus, a proteasome-dependent proteolytic pathway appears to play an important role in the enhanced production of endothelin-1 in blood vessels and the consequent increase in blood pressure in this model of hypertension.     

Phosphatidylinositol 4-kinase of Torpedo californica electrocytes: physico-chemical characterization and regulation by calcium and vicinal molecules of phosphatidylinositol

The kidney is an important target of hypertension-induced organ damage. Recent long-term observation studies have documented that in individuals, without primary chronic renal disease, a very significant relationship exists between hypertension and impaired renal function, elderly hypertensives having a particularly worse prognosis. The hallmark of hypertensive renal injury is thought to be a progressive increase in intrarenal vascular resistance. The alterations in renal hemodynamics are accentuated in elderly patients with essential hypertension, pointing to a greater vulnerability of the senescent kidney to superimposed injury such as high blood pressure. Treatment of elevated blood pressure in the elderly therefore not only reduces cardiovascular morbidity and mortality, but also reduces the incidence of renal failure as a consequence of hypertension-induced damage.     

Renal and vascular effects of chronic endothelin receptor antagonism in malignant hypertensive rats

The effect of the combined ETA/ETB endothelin receptor antagonist bosentan on blood pressure, vascular hypertrophy, and pathologic renal changes was investigated in a model of malignant hypertension, severe vascular hypertrophy, and enhanced vascular expression of endothelin-1, the deoxycorticosterone acetate (DOCA), and salt-treated spontaneously hypertensive rat (SHR). DOCA-salt treated SHR received 100 mg bosentan per kilogram weight per day mixed with their food. Systolic blood pressure of untreated DOCA-salt SHR rose to 241 +/- 1.5 mm Hg, whereas that of bosentan-treated rats rose to 221 +/- 5.1 mm Hg (P < .01). Cardiac and conduit artery mass were not affected by treatment. Small arteries from the coronary, renal, and mesenteric circulations showed a smaller media width and cross-sectional area of the media in rats treated with bosentan than in untreated rats. The kidneys showed the presence of fibrinoid necrosis in a high percentage of afferent arterioles and glomeruli of untreated DOCA-SHR. Some kidneys of treated rats exhibited less severe vascular hypertrophy and lesser extent of vascular or glomerular fibrinoid necrosis, but the renal injury score of bosentan-treated DOCA-SHR was only at the limit of significance from that of untreated rats (P = .06). These results suggest a role for endothelin-1 in blood pressure elevation and the severe vascular hypertrophy of small arteries of the coronary, renal, and mesenteric vasculature, but not of the heart or larger conduit vessels in the malignant hypertension that SHR develop after treatment with DOCA and salt. Although some bosentan-treated rats showed fewer renal lesions, a significant effect on renal pathology could not be unambiguously demonstrated. Further studies will be necessary to determine whether endothelin antagonists may indeed offer some degree of renal protection and have therapeutic potential in severe or malignant hypertension.     

Growth hormone release of interleukin-1 alpha, interferon-gamma and interleukin-4 from murine splenocytes stimulated with staphylococcal protein A, toxic shock syndrome toxin-1 and streptococcal lysin S

1. The role of the renin-angiotensin system in long-term control of sympathetic activity and arterial pressure is reviewed. 2. There is evidence that favours a necessary role for the sympathetic nervous system in long-term arterial pressure regulation. First, appropriate changes in sympathetic activity appear to be produced in response to chronic changes in blood volume or blood pressure. Second, prevention of the normal homeostatic decrease in sympathetic activity in response to an increase in sodium intake produces hypertension. 3. Long-term changes in sympathetic activity cannot be mediated by the baroreceptor reflex, because it adapts to sustained changes in pressure. Therefore, an hypothesis is presented that evokes a key role for angiotensin II (AngII) in determining the chronic level of sympathetic activity. The key feature of this model is that the role of AngII is non-adaptive: chronic changes in extracellular fluid volume produce sustained reciprocal changes in AngII, and long-term increases in AngII produce sustained increases in sympathetic activity. 4. Evidence is reviewed that suggests that a lack of the normal suppression in AngII and/or sympathetic activity in response to an increase in sodium intake produces salt-sensitive hypertension.     

Intrauterine contraceptive devices. Mode of action, experiences, complications (author''s transl)

Effects of norethisterone (NT) purified norethisterone (pure NT), norethynodrel (NE), medroxyprogesterone acetate (MAP), chlormadinone acetate (CMA) and desoxycorticosterone acetate (DOCA) on serum and liver lipid levels and serum lipoproteins were examined in both intact and estradiol-treated male rats. NT and NE caused a decrease in serum cholesterol and phospholipid levels, an increase in liver cholesterol level, no significant change in triglyceride levels of both serum and liver, with a significant change in serum lipoprotein patterns; a decreased in alpha- and beta-lipoproteins and a marked increase in pre beta-lipoprotein. Pure NT decreased serum cholesterol without causing any change in lipoprotein pattern. MAP, CMA and DOCA causee almost no effect on lipid levels in serum and liver, but CMA and DOCA increased alpha-lipoprotein and decreased beta- and pre beta-lipoproteins. An acute treatment with estradiol caused a decrease in alpha- and beta-lipoproteins and an increase in pre beta-lipoprotein with a decrease in serum lipid levels and an increase in liver lipids. By contrary, a chronic treatment with a marked hypercholesterolemia. This increase of alpha-lipoprotein in estradiol-treated rats was prevented by NT and NE, not affected or rather decreased by MAP but further increased with CMA and DOCA. These data suggest that the effects of synthetic progestational steroids on lipids are classified into two groups, 19-nortestosterone derivatives and 17alpha-hydroxyprogesterone derivatives including DOCA. The former caused a decrease in serum lipid levels with an increase of pre beta-lipoprotein and adecrease of alpha-lipoprotein. The latter caused almost no change or a slight increase in serum lipid levels with a decrease in pre beta-lipoprotein and an increase in alpha-lipoprotein, though it was not found in MAP.     

Effect of blockade of angiotensin II on blood pressure, renin and aldosterone in cirrhosis

1-Sar-8-ala angiotensin II (saralasin) was infused intravenously in graded doses of from 0.1 to 10 mug/kg/min to five patients with cirrhosis and ascites after three days of restricted sodium intake. In each patient blockade of AII by saralasin produced a marked fall in blood pressure, a rise in plasma renin activity (PRA) and plasma renin concentration (PRC) and, in four of the five, a fall in plasma aldosterone (PA). The rise in PRA and PRC correlated poorly with changes in blood pressure. The effects of saralasin rapidly reversed after cessation of the infusion. Plasma volume was normal or high in each case. Three patients were mildly hypotensive in the control state, and all five were resistant to the pressor effect of infused AII. After three days of salt loading, the above effects of saralasin were diminished but not abolished. In four normal subjects, after salt depletion, saralasin infusion induced qualitatively similar but much smaller changes in blood pressure, PRA and PRC. In two cirrhotic patients without ascites, after salt depletion, saralasin infusion caused a rise in blood pressure with no significant changes in PRA, PRC or PA. These results provide evidence that in patients with cirrhosis and ascites circulating AII is active in support of blood pressure, in direct suppression of renal renin release, and in stimulation of aldosterone release.     

The development of the thymus gland in rat embryogenesis with progesterone administration

Thymus structure was studied in 16 and 20-days-old embryos after everyday administration of 0,3 microgram (treatment doze) and 3,0 micrograms/100 g body weight of progesterone. It was established by morphologic methods that on 16th day blast forms amount in experimental animals is significantly lower than that in control animals. Amount of the hormone, 10 times exceeding the previous ones was administered in the same terms and caused reduction of the mitotic activity. The data on the cell by that time were absent. Progesterone administration during placenta forming does not change neither does thymus location nor its structure in 20-days-old foetuses. Treatment doze causes increase of the share of the section area occupied with the cortical matter. 10-times exceeding doze results in more significant decrease of the lymphoid cells number than those caused by treatment doze. Progesterone dissolvent (apricot oil) does not cause significant changes in thymus structure indexes studied. Thus, changes in the thymus structure observed result from progesterone effect on the thymus rudiment during placenta forming.     

Nocturnal blood pressure and relation to vasoactive hormones and renal function in hypertension and chronic renal failure

The purpose of this study was to assess the blood pressure profile and to measure vasoactive hormones in patients with essential hypertension (n=61), secondary hypertension (n=32) and chronic renal failure (n=32) matched with healthy control subjects (n=35), and to study the relationship between circadian changes in blood pressure and baseline levels of vasoactive hormones and renal function. Non-invasive, automatic blood pressure measurement was performed for 24 or 48 h. Venous plasma concentrations of renin, angiotensin II, aldosterone, arginine vasopressin, atrial natriuretic peptide and endothelin were measured. The mean 24-h blood pressure was higher in all groups of hypertensive patients than in control subjects. The nocturnal blood pressure fall was preserved in essential hypertension, in contrast to secondary hypertension in which it was attenuated. In the patients with chronic renal failure the 24-h mean blood pressure was the same as in the controls. Night-time blood pressure was higher among the chronic renal failure patients than in the control group, and the nightly blood pressure fall in both diastolic and systolic blood pressure was reduced. Plasma concentrations of renin activity, arginine vasopressin, atrial natriuretic peptide, aldosterone and endothelin were significantly increased in secondary hypertension and chronic renal failure, compared to essential hypertension and control subjects. Plasma angiotensin II was increased in chronic renal failure compared to essential hypertension and controls. Estimated creatinine clearance and nightly blood pressure dips were inversely correlated in essential and secondary hypertension, i.e. with a decreasing renal function both systolic and diastolic nightly blood pressure dips were gradually attenuated. In the whole group of patients the nightly systolic and diastolic blood pressure dips were negatively correlated to basal plasma renin activity, plasma aldosterone and atrial natriuretic peptide levels, i.e. the higher the basal plasma hormone level the lower the blood pressure dip. In conclusion, patients with essential hypertension have elevated but normally configured 24-h blood pressure profiles, and patients with different kinds of secondary hypertension have elevated 24-h blood pressure profiles and attenuated nightly systolic and diastolic blood pressure falls. The more the renal function is reduced and the more the plasma levels of renin and aldosterone are increased, the more the nocturnal fall in blood pressure is reduced. It is suggested that the attenuated or absent decrease in nocturnal blood pressure in secondary renal hypertension is caused by an abnormally increased secretion of vasoactive hormones and/or by so far unknown factors released from the diseased kidney.     

Opposite role of interferon-gamma and interleukin-4 on the regulation of blood pressure in mice

There is growing evidence that T-lymphocyte dysfunction contributes to the development of hypertension. IL-4 and IFN-gamma are important regulators of T-lymphocyte function. Therefore, we investigated the effect of neutralizing antibodies against IL-4 (alpha-IL-4) and IFN-gamma (alpha-IFN-gamma) on the development of hypertension in NZBNZWF1 hybrid compared to normotensive NZW control mice. Antibody-producing cells were encapsulated and injected intraperitoneally in mice at 6,8 and 10 weeks of age. This treatment resulted in significant levels of antibody in the serum. At 12 weeks of age blood pressure was recorded under anesthesia. Mean arterial blood pressure (MAP) increased in NZBNZWF1 hybrids between the age of 6 and 12 weeks. This increase was inhibited by treatment with alpha-IL-4, but was not affected by alpha-IFN-gamma. Treatment with alpha-IL-4 did not influence MAP in normotensive NZW or C57B1/6J mice. However, in these mice, treatment with alpha-IFN-gamma increases MAP. This increase in MAP by alpha-IFN-gamma was prevented by simultaneous treatment with alpha-IL-4. The present study demonstrates the influence of endogenous IL-4 and IFN-gamma on blood pressure.     

Immunohistochemical detection of parathyroid hormone-related protein in human astrocytomas

Hypertension is more common among African Americans than Americans of European descent. However, the genetic etiology has not been defined. Similarly, lipoprotein (Lp) (a), an independent risk factor for cardiovascular disease, is higher among African Americans. To explore the relationship between Lp (a) and hypertension, we measured the blood pressure of transgenic mice expressing apolipoprotein(a), the unique protein moiety of lipoprotein(a). As controls, we also determined blood pressure for apoE deficient mice, low density lipoprotein-receptor (LDL-R) deficient mice, and wild type C57Bl/6 mice. Apo(a) expression was not associated with hypertension. Surprisingly, LDL-R deficient mice exhibited male-associated hypertension. This observation could explain the higher incidence of atherosclerosis in male LDL-R deficient mice and human familial hypercholesterolemia (FH) patients. LDL-R deficient mice were more sensitive to photochemically induced cerebral stroke. However, this hypersensitivity was only modestly associated with sexual dimorphism. The presented data suggest that LDL-R deficiency results in hitherto unrecognized changes in the vascular tone.