Prolactin release by vasoactive intestinal polypeptide in rats

Synthetic vasoactive intestinal polypeptide (VIP) administered either intraventricularly or iv caused a significant and dose-related increase in plasma PRL levels in urethane-anesthetized rats. The administration of naloxone, an opiate receptor antagonist, significantly blunted the plasma PRL response to VIP. Increases in plasma PRL induced by VIP were also significantly suppressed by L-dopa, a precursor of dopamine, whereas pilocarpine, a cholinergic agonist, diphenhydramine, a histamine antagonist, and cyproheptadine, an antiserotoninergic agent, did not affect the plasma PRL response to VIP. In in vitro experiments, VIP alone did not stimulate PRL release from cultured pituitary cells, but it significantly attenuated the inhibitory action of dopamine, which was not blocked by naloxone. These results suggest that VIP stimulates rat PRL secretion, at least in part, through activation of an opiate receptor in the central nervous system and by blocking the inhibitory action of a dopaminergic mechanism at the pituitary level.     

Characterization of the effects of retinoic acid on vasoactive intestinal polypeptide gene expression in neuroblastoma cells

The neuropeptide vasoactive intestinal polypeptide (VIP) has a broad range of functions, and its expression has been correlated with neuronal differentiation. Here we present data on the effects of retinoic acid (RA), a known modulator of neuronal differentiation, on VIP gene expression in the human neuroblastoma cell line NB-1. Morphological data, surprisingly, indicate that these cells are not differentiated concomitant with the increase in VIP gene expression. RA was found to exert a concentration-dependent induction of peptides derived from the VIP precursor molecule, prepro-VIP. The effect at both the messenger RNA (mRNA) level, evaluated by Northern blots, and the peptide level, measured by RIAs, was found to be slow and long lasting. No changes in the processing of prepro-VIP were observed using gel chromatography and RIAs specific for various prepro-VIP sequences. Also, the expression of mRNA for the prohormone-processing enzyme PC2, present in these cells, was not altered by RA. The lag period preceding the increase in VIP mRNA led to experiments with the translational inhibitor cycloheximide showing an indirect effect of RA on VIP mRNA expression. Northern blots revealed that at least three mRNAs encoding RA receptor were expressed and rapidly induced by RA in the cells, thus making them possible candidates for the intermediate protein(s) required from the induction of VIP gene expression.     

Effects of pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal polypeptide on cyclic AMP accumulation in sheep pituitary cells in vitro

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are known to stimulate adenylate cyclase activity in rat pituitary cells but no direct effects have been reported on sheep pituitary cells. In this study we determined whether either peptide could stimulate intracellular cAMP accumulation in dispersed sheep pituitary cells in primary culture. Time course studies with PACAP showed that tachyphylaxis developed rapidly and so a short incubation time (5 min) was used to define the dose-response relationship. PACAP dose-dependently stimulated intracellular cAMP levels with a half-maximum response at 2.9 +/- 0.2 nmol/l (n = 4). In contrast, VIP only caused a small increase in intracellular cAMP levels at the highest dose tested (1 mumol/l). The VIP antagonist [4Cl-D-Phe6,Leu17]VIP had no effect on the cAMP response to either PACAP or VIP while the peptide PACAP(6-38), a putative PACAP antagonist, blocked the cAMP response to PACAP. The desensitisation to PACAP was further investigated by pretreating cells with PACAP for 30 min. After a further 15 min in culture medium alone, these cells showed no cAMP response to subsequent treatment with PACAP but could respond to forskolin. When a longer incubation period of 240 min was used between the first and second treatment with PACAP, a partial return in responsiveness to PACAP was observed. In summary, these results show that PACAP activates adenylate cyclase in sheep pituitary cells but that there is rapid development of tachyphylaxis. Experiments with the antagonists suggest that the response to PACAP is via the PACAP type I receptor. In contrast, physiological doses of VIP do not stimulate cAMP accumulation in sheep pituitary cells.     

Role of nitric oxide and vasoactive intestinal polypeptide in vagally mediated relaxation of the gastric corpus in the anaesthetized ferret

We have examined the role of protein kinase C (PKC) in the stimulation of protein synthesis by insulin using two complementary approaches. In the first, fibroblasts were pretreated with phorbol esters to down-regulate PKC. In these cells, the effects of insulin and of phorbol esters on protein synthesis were completely abolished, although serum still elicited an effect approaching that seen in control cells. Secondly, we used newly developed inhibitors of PKC which, again, blocked the effects of insulin and phorbol esters without greatly reducing the response to serum. Thus PKC apparently plays an important role in the stimulation of translation by insulin.     

Pituitary adenylate cyclase-activating polypeptide, helospectin, and vasoactive intestinal polypeptide in human corpus cavernosum

1. The distribution and effects of pituitary adenylate cyclase-activating polypeptide (PACAP-27 and -38), helospectin (Hel-1 and Hel-2), and vasoactive intestinal polypeptide (VIP), were investigated in isolated preparations of human corpus cavernosum (CC). 2. Immunohistochemistry revealed coinciding profiles of nerve structures that showed immunoreactivities for VIP and PACAP, and VIP and Hel. Confocal microscopy showed the co-existence of VIP- and PACAP-immunoreactivities, and VIP- and Hel-immunoreactivities in most (90%) varicose nerve structures. 3. As determined by radioimmunoassay, the amounts of VIP, PACAP-27, and PACAP-38 in the preparations were 61.7 +/- 11.6, 0.1 +/- 0.05, and 3.7 +/- 0.5 pmol g-1 wet weight of tissue (pmol g-1 wet wt.), respectively. In tissue from patients with diabetes, the content of VIP was lower (13.7 +/- 0.5 pmol g-1 wet wt.), whereas that of PACAP (-27 and -38) was unchanged. 4. Cyclic nucleotide levels were determined in preparations exposed to PACAP-27, PACAP-38, Hel-1, Hel-2, and VIP. All the peptides, but Hel-2, significantly increased the concentrations of cyclic AMP, whereas the levels of cyclic GMP were unchanged. 5. The peptides concentration-dependently relaxed noradrenaline-contracted preparations. The order of potency was VIP > PACAP 27 > Hel-1 > Hel-2 > PACAP-38. 6. Hel-1, VIP and PACAP-27 effectively counteracted electrically induced contractions. At 10(-6) M, the highest peptide concentration used, the inhibitory effects obtained reached 96 +/- 3%, 87 +/- 6%, and 80 +/- 3%, respectively. 7. The results suggest that PACAP and Hel-1 are co-localized with VIP in nerve structures within the human cavernous tissue, and that the peptides are effective relaxants of CC preparations in vitro. The role of the investigated peptides for penile erection remains to be established.     

Effects of vasoactive intestinal polypeptide on heart rate in relation to vagal cardioacceleration in conscious dogs

OBJECTIVE: The vagal cardiac accelerator (VCA) system takes part in the nervous control of the heart rate. In the present study we tried to adduce evidence that vasoactive intestinal polypeptide (VIP) contributes to vagally induced cardioaccelerations. METHODS: The effect of VIP on heart rate and arterial blood pressure was investigated after unmasking the inherent VCA activity by blocking the sympathetic accelerator and vagal decelerator influences on heart rate in conscious dogs. RESULTS: Following intravenous administration of VIP (10 micrograms i.v.) the heart rate increased by 43.6 +/- 6.7 (28.1 +/- 4.7%), from 165.6 +/- 8.5 to 209.1 +/- 7.0 beats/min (P < 0.001) and the mean arterial blood pressure decreased by 47.5 +/- 3.2 (37.9 +/- 3.0%), from 126.6 +/- 2.6 to 79.1 +/- 4.9 mmHg (P < 0.001) (n = 11). After VCA activity was reflexly enhanced by alpha 1-adrenoceptor stimulation with methoxamine, VIP increased heart rate by 36.9 +/- 7.3 (21.5 +/- 4.6%), from 179.8 +/- 5.2 to 216.7 +/- 5.8 beats/min (P < 0.001) and decreased mean arterial pressure by 79.1 +/- 6.4 (46.7 +/- 3.5%), from 168.2 +/- 4.1 to 89.1 +/- 5.0 mmHg (P < 0.001). Hence, the VIP-induced tachycardia, expressed in relative values, shows a significant attenuation after the administration of methoxamine (P < 0.05). The increase in heart rate induced by VIP appeared to be inversely related to the prevailing VCA activity, both before (r = -0.744, P = 0.009) and after methoxamine (r = -0.689, P = 0.019). The VIP-induced tachycardia is certainly not reflexly induced by the fall in arterial pressure, because intracoronary administration of VIP (0.5 microgram i.c.) caused an appreciable increase in the heart rate by 63.7 +/- 13.0 (46.4 +/- 10.4%), from 143.0 +/- 8.1 to 208.7 +/- 12.0 beats/min (P < 0.005), whereas the mean arterial pressure only slightly changed (-7.7 +/- 2.0 mmHg) (P < 0.05) (n = 6). In addition, VIP (10 micrograms i.v.) also caused a tachycardia in vagotomized dogs with blocked beta-adrenergic and muscarinic receptors. The administration of the VIP antagonists [D-p-CI-Phe6, Leu17]-VIP (50-150 micrograms i.c.) and [Lys1, Pro2,5, Leu17]-VIP (20 micrograms i.c.) did not result in alterations in VCA activity nor did the VIP antagonists block the VCA reflex response to a rise in arterial pressure. However, none of the VIP antagonists reduced the VIP-induced tachycardia either. CONCLUSION: Vasoactive intestinal polypeptide is likely to play a part in the vagal cardiac accelerator system. However, conclusive evidence for its role as the terminal transmitter in the VCA pathway will have to wait for the availability of a specific cardiac VIP receptor antagonist.     

Activation of T lymphocytes by syngeneic murine intestinal smooth muscle cells

BACKGROUND & AIMS: Intestinal smooth muscle cells (ISMCs) express major histocompatibility complex II (MCH II) and intercellular adhesion molecule 1 (ICAM-1) after exposure to interferon gamma (IFN-gamma). T lymphocytes invade the intestinal musculature during Crohn's disease or pseudoobstruction. The aim of this study was to determine whether ISMCs activate syngeneic T cells via MHC II and ICAM-1. METHODS: Cultured murine ISMCs were exposed to IFN-gamma for 72 hours and analyzed for Mac-1 (CD11B CD18) antigen, MHC II, and ICAM-1 expression using enzyme-linked immunosorbent assay and fluorescence-activated cell sorter scan. T lymphocytes from mesenteric lymph nodes of ovalbumin-sensitized mice were examined for their ability to proliferate after coculture with IFN-gamma-pretreated and ovalbumin-pretreated ISMCs using [3H]thymidine incorporation. RESULTS: ISMCs expressed smooth muscle alpha-actin before and after IFN-gamma exposure. No macrophages were identified in these cultures. Exposure to IFN-gamma and ovalbumin for 72 hours induced MHC II and ICAM-1 expression; these treated ISMCs induced T-cell proliferation, whereas untreated ISMCs did not. T-cell proliferation was markedly enhanced by adding interleukin 2 and was blocked by antibodies against MHC II and ICAM-1. CONCLUSIONS: ISMCs activate T lymphocytes in an MHC II-linked manner and thus possess the ability to modulate immune function in the gut.     

Contraction and intracellular calcium-ion elevation of cultured human aortic smooth muscle cells by endothelin-1, vasoactive intestinal contractor (VIC) and the derivatives

Effects of endothelin (ET) family peptides and their derivatives on cellular contraction and calcium-ion level were examined by using cultured human vascular smooth muscle cells (VSM). Contraction of cultured human VSM, isolated from human fetal aortic segments, was induced within 1 min after the treatment with ET-1 (100 nM) as seen in the changes of cytosolic calcium-ion localization. In parallel with the cell contraction, cytosolic calcium-ion level in the human VSM increased very rapidly and then dropped with some oscillation as determined by Anchorage Cell Analyzing System. It was noted that transient calcium-ion mobilization rather than sustained calcium-ion influx was significant in the contraction of cultured human VSM. Vasoactive intestinal contractor (VIC), three amino acids different from ET-1, had less activity in increase of intracellular calcium-ion level and in percent of response cells than ET-1, ET-2, and VIC-S4L6 (one amino acid different from ET-1). EC50 of ET-1, VIC-S4L6, ET-2, and VIC were 0.5 nM, 0.6 nM, 2.0 nM, and 20 nM, respectively. VIC-like peptide (VIC-LP), 16 amino acids fragment of VIC precursor protein, had no effect with a single administration of up to 10 microM. However, the increase in calcium-ion level by VIC was suppressed with a prior treatment of cells with high concentration (10 microM) of VIC-LP. The establishment of cultured human VSM for the simultaneous examination of the contraction and calcium-ion level will provide a new system to study signal transduction of vasocontractor peptides.     

Fluoride activates G protein-dependent and -independent pathways in dispersed intestinal smooth muscle cells

The existence of G protein-dependent and -independent mechanisms activated by sodium fluoride was examined in muscle cells isolated separately from the circular and longitudinal layers of guinea pig intestine. The cells were transiently permeabilized by incubation with Trans. Port Reagent in the presence or absence of GDP beta S (100 microM) and then re-sealed. In the absence of GDP beta S, NaF (1 mM) induced contraction and caused an increase in [Ca2+]i, IP3 and diacylglycerol levels and in protein kinase C (PKC) activity in both cell types. In the presence of GDP beta S, the increases in IP3, DAG and PKC were abolished whereas contraction and the increase in [Ca2+]i were partly inhibited. Residual contraction and [Ca2+]i were abolished by the Ca2+ channel blocker, methoxyverapamil. We conclude that contraction and Ca2+ mobilization induced by NaF is mediated by G protein activation as well as by a G protein-independent mechanism involving activation of plasmalemmal Ca2+ channels.     

Pharmacological, molecular and functional characterization of vasoactive intestinal polypeptide/pituitary adenylate cyclase-activating polypeptide receptors in the rat pineal gland

Melatonin secretion from the mammalian pineal gland is strongly stimulated by noradrenaline and also by vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Three types of receptors for VIP and PACAP have been characterized so far: VIP1/PACAP receptors and VIP2/PACAP receptors, which possess similar high affinities for VIP and PACAP, and PACAP1 receptors which exhibit a 100-1000-fold higher affinity for PACAP. The aim of the present study was to characterize the receptor subtype(s) mediating the stimulatory effects of VIP and PACAP on melatonin synthesis in the rat pineal gland. Autoradiographic studies showed that PACAP and VIP were equally potent in displacing binding of radioiodinated PACAP27 from pineal sections. Amplification of pineal complementary DNAs by polymerase chain reaction using specific primers for the different receptor subtypes revealed that all three receptor messenger RNAs are expressed and that VIP1/PACAP receptor messenger RNA was predominant over VIP2/PACAP receptor messenger RNA. In vitro, VIP and PACAP stimulated melatonin synthesis with similar high potency and the effect of the two peptides were not additive. The selective VIP1/PACAP receptor agonists [R16]chicken secretin (1-25) and [K15, R16, L27]VIP(1-7)/growth hormone releasing factor(8-27) were significantly more potent than the selective VIP2/PACAP receptor agonist RO 25-1553 in stimulating melatonin secretion. The stimulatory effects of VIP and PACAP were similarly inhibited by the VIP1/PACAP antagonist [acetyl-His1, D-Phe2, K15, R16, L27]VIP(3-7)/growth hormone releasing factor(8-27). These data strongly suggest that VIP and PACAP exert a stimulatory effect on melatonin synthesis mainly through activation of a pineal VIP1/PACAP receptor subtype.     

Desmin-rich smooth muscle bundles in chronic intestinal pseudo-obstruction

OBJECTIVE: To report a case of hypocalcemia and hypomagnesemia after ibuprofen overdose. CASE SUMMARY: A 21-month-old boy developed acute renal failure with severe metabolic acidosis after ingestion of ibuprofen 8 g. The infant developed tonic-clonic seizures 46 hours after ingestion, with significant hypocalcemia and hypomagnesemia that required electrolyte replacement to control the seizures. DISCUSSION: To our knowledge this is the first case report of hypocalcemia, hypomagnesemia, and seizures in a patient after ibuprofen overdose. The mechanism is unclear, the situation was probably aggravated by the use of sodium polystyrene sulfonate and furosemide. CONCLUSIONS: In patients with ibuprofen overdose, serum calcium and magnesium concentrations should be evaluated since seizures may be associated with a deficiency of these cations. The management of these patients should include calcium and/or magnesium supplementation when required and furosemide should be avoided.     

Different effects of visual deprivation on vasoactive intestinal polypeptide (VIP)-containing cells in the retinas of juvenile and adult rats

Vasoactive intestinal polypeptide (VIP) is a 28 amino acid peptide that has been shown to be present in a distinct subset of retinal amacrine cells (VIP+ cells). Previous work has suggested that the expression of retinal VIP might depend on the lighting conditions prevailing. Reasoning that a careful analysis of the exact conditions of this interaction and its time course might offer clues to the functional role of retinal VIP, we performed a quantitative immunohistochemical analysis of the effects of visual deprivation on the retinal VIP+ system in adult and in visually inexperienced neonatal rats. In adult rats visual deprivation caused a marked suppression of VIP-like immunoreactivity (IR) in both somata and processes of VIP+ cells which increased linearly over time, reducing the number of VIP+ cells to about 30% of the control value after approximately 50 days of deprivation. The observed changes were specific for VIP and were independent of the form of deprivation used (monocular lid suture versus keeping rats in constant darkness). However, the effects of visual deprivation were dependent on the developmental state of the rats, since juvenile rats without previous visual experience exhibited a decrease in VIP+ cells and fibers which was much smaller and occurred significantly slower than in adult rats. The suppression of VIP-like IR was completely reversible in both juvenile and adult rats when previously deprived rats were returned to a normal visual environment.     

Neurogenic relaxation mediated by vasoactive intestinal polypeptide (VIP) in the isthmus of the human fallopian tube

The smooth musculature of the Fallopian tube is important for normal ovum transport, fertilization and implantation. Little is known about the factors controlling the motor activity of the isthmic sphincter. Studies were performed on smooth muscle preparations from the human tube in vitro. Electrical field stimulation of the nerves in the isthmic region reduced the motor activity, particularly in the circular muscle. The response was unaffected by adrenergic and cholinergic antagonists, but blocked by tetrodotoxin, suggesting a neural involvement. Vasoactive intestinal polypeptide (VIP) was considered a likely candidate for the neural mediation of this response in view of the high density of VIP-containing nerve fibres in this region, and in view of the fact that exogenous VIP causes a marked reduction of the tubal motor activity. To test whether VIP might be the endogenous mediator of this effect, nerve stimulation was carried out in the presence of large amounts of exogenous VIP in order to occupy all VIP receptors; the motor inhibitory action of VIP was counteracted by vasopressin. Under these conditions, nerve stimulation failed to reduce isthmic motor activity. This was not due to vasopressin since reduction occurred in the presence of this peptide alone. The results suggest that VIP is responsible for the neurogenic inhibition of motor activity in the isthmus region of the human Fallopian tube.     

Rectal adaptation to distension in patients with overt rectal prolapse

BACKGROUND: High recovery rates of continence are observed after surgical procedures for rectal prolapse. Increases in rectal compliance but no obvious rise in anal pressures have been reported. The authors' hypothesis was that decreased rectal adaptation to distension may contribute to incontinence in patients suffering from overt rectal prolapse. METHODS: This was a prospective study conducted in 20 consecutive incontinent patients suffering from overt rectal prolapse with no mucosal change (two men and 18 women; mean(s.e.m.) age 50(3) years). They were compared with 20 age- and sex-matched patients with incontinence without rectal prolapse and ten age- and sex-matched healthy volunteers observed during the same period. The subjects were submitted to phasic isobaric distension of the rectum with an electronic barostat. Anal pressures, perception scores and rectal volumes were recorded at six different preselected pressures. RESULTS: Compared with healthy subjects, maximum rectal volumes (mean(s.e.m) 98(6) versus 167(11) ml; P= 0.005), volumes related to compliance (56(5) versus 100(9) ml; P= 0.004) and tone (41(3) versus 67(4) ml; P = 0.003) were decreased significantly in the rectal prolapse group. Prolapse and incontinence groups did not differ significantly with respect to rectal adaptation for all three parameters and steps of distension considered. CONCLUSION: Patients suffering from overt rectal prolapse had markedly impaired rectal adaptation to distension which may contribute to incontinence.     

Involvement of pituitary adenylate cyclase-activating polypeptide II vasoactive intestinal peptide 2 receptor in mouse neocortical astrocytogenesis

At the end of neuronal migration, the neopallial germinative zone produces glial cells destined to colonize the upper layers of neocortex. High densities of binding sites for vasoactive intestinal peptide (VIP) have been found in the rodent germinative zone just after completion of neuronal migration, suggesting a possible role of VIP in neocortical astrocytogenesis. In the present study, administration of a VIP antagonist at embryonic days 17 and 18 to pregnant mice was followed by a dramatic depletion of astrocytes in the upper cortical layer of the offspring. The depletion of astrocytes was dose-dependent, with a 42% reduction in the density of astrocytes observed with 50 microg of antagonist. The antagonist effect was reversed by cotreatment with VIP or pituitary adenylate cyclase-activating polypeptide (PACAP), suggesting the involvement of a receptor common to these two neuropeptides. VIP antagonist-induced inhibition of astrocytogenesis was also blocked by Ro 25-1553, a long-acting cyclic VIP analogue selective for the PACAP II VIP2 receptor subclass. Our results demonstrate that VIP and/or PACAP play a crucial physiological role in neocortical astrocytogenesis, possibly through interaction with PACAP II VIP2 receptors.     

Ultrastructural co-localization of neuropeptide Y and vasoactive intestinal polypeptide in neurosecretory vesicles of submucous neurons in the rat jejunum

The localization of vasoactive intestinal polypeptide and neuropeptide Y in submucous nerves of rat jejunum was studied using both single-label pre-embedding immunocytochemistry and post-embedding double-label immunogold techniques. Vasoactive intestinal polypeptide-immunoreactive fibres and cell bodies were regularly observed in submucous plexus and a similar distribution was seen for neuropeptide Y. Varicose fibres were observed in single-label studies and when areas of specific interest were subjected to double-label immunogold protocols these immunoreactive profiles exhibited vesicles clearly stained for both vasoactive intestinal polypeptide and neuropeptide Y. Synaptic vesicles in immunopositive fibres observed close to the mucosa (and elsewhere in the submucosa) were dense-cored with an average diameter of 80 nm. Nerves associated with vascular elements only stained for neuropeptide Y, not for vasoactive intestinal polypeptide. These findings suggest that these two unrelated enteric peptides are co-released in the vicinity of the mucosal lining and the likely implications of such co-release are discussed.     

Role of caveolae in cholesterol transport in arterial smooth muscle cells exposed to lipoproteins in vitro and in vivo

Arterial smooth muscle cells are able to shift between two major differentiated states with distinct morphologic and functional properties, a contractile phenotype and a synthetic phenotype. Recently, it was demonstrated that contractile smooth muscle cells have numerous caveolae and that these specialized regions of the plasma membrane, to a large extent, are lost when the cells are modified into a synthetic phenotype. At the same time, the levels of the cholesterol-binding membrane protein caveolin remained unchanged and caveolin was redistributed from the cell surface to the perinuclear cytoplasm. In the present investigation, electron microscopy was used to study how smooth muscle cells of different phenotypes react to exposure to low-density lipoprotein and other lipoproteins both in vitro and in vivo. Our findings indicate that contractile cells (present early in primary culture and in the media of normal arterial walls) do not accumulate lipids in the cytoplasm and release excess cholesterol by means of plasma membrane caveolae. Extracellularly, the expelled lipids were built into membranous configurations and piled up as myelin-like deposits. In synthetic cells (formed after a few days in primary culture and as a response to arterial injury), lipids gathered in cytoplasmic droplets and increased amounts of membranous inclusions appeared in endosomes and lysosomes. On the other hand, no signs of extracellular discharge of lipids were detected. The results suggest that contractile smooth muscle cells use caveolin and caveolae to free themselves of excess lipoprotein-derived cholesterol and so manage to maintain a balance in the influx and efflux of cholesterol. Synthetic smooth muscle cells show a Golgi-like immunostaining for caveolin but have an insufficient capacity to use this protein to transport cholesterol to the plasma membrane and out of the cell. Cholesterol will then rather be esterified and collect in lipid droplets, eventually leading to foam cell formation if the uptake of lipoprotein continues.     

Studies on the composition of phospholipids in rat small intestinal smooth muscle

The phospholipid composition of rat small intestinal smooth muscle was investigated in comparison with those of the mucosa and liver. Phospholipid content per g of the wet smooth muscle was almost identical with that of the mucosa and was about 1/4 of that in the liver. The phospholipid/protein ratio of the smooth muscle was about 1/2 of the value in the liver. Sphingomyelin content was significantly high and amounted to 18% of total phospholipids. This value was about twice that in the mucosa and 4 times higher than that in the liver. On the other hand, the percent distribution of phosphatidylcholine was lowest in the smooth muscle. Distribution patterns of phosphatidylserine and phosphatidylinositol in the smooth muscle as well as in the mucosa were different from those in the liver. The occurrence of vinyl-ether and ether phospholipids was clearly demonstrated in the smooth muscle as well as in the mucosa. A major part of the ether lipids was detected in the phosphatidylethanolamine fraction, in which they amounted to about 50%; 40% as alkenyl-acyl type and 12% as alkyl-acyl type. A high content of ether lipids was also observed in the phosphatidylethanolamine fraction from mucosa, but the distribution was reversed, that is, 14% alkenyl-acyl type and 28% alkyl-acyl type. Fatty aldehydes, fatty alcohols, and fatty acids were also determined by gas-liquid chromatography. The compositions of fatty aldehydes in the phosphatidylethanolamine fraction from smooth muscle and from mucosa were similar, whereas the compositions of long chain fatty alcohol and fatty acids were clearly different. The compositions of fatty alcohols and fatty acids of the phosphatidylcholine fraction from smooth muscle showed significantly different patterns from those of the phosphatidylethanolamine fraction and from those of the same phospholipid fraction in the mucosa.