Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.24.3 (collagenase)
18,340 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Somatostatin (SRIF), a tetradecapeptide, has been reported to suppress gastrin release and hence inhibit acid secretion in vivo. This study was performed to determine whether SRIF has any direct effect on parietal cell (PC). Isolated gastric cells were prepared by collagenase digestion and calcium chelation of rabbit fundic mucosa. PC enrichment (75% +/- 5%) was accomplished by velocity sedimentation with an elutriator rotor. Acid, as assessed by the accumulation of 14C-aminopyrine (AP) and macromolecular (intrinsic factor [IF]) secretion were used as markers of PC function. Cells were stimulated with histamine (H) (10(-6) mol/L). SRIF (10(-10) to 10(-6) mol/L) significantly inhibited H-stimulated 14C-AP accumulation (p less than 0.05). Inhibition of H-stimulated IF release was less sensitive, occurring at 10(-8) and 10(-7) mol/L (p less than 0.05), and loss of inhibition was observed at 10(-6) mol/L (p less than 0.05). These results demonstrate a direct inhibitory action of SRIF on PC secretion. The difference in inhibitory effect on IF and proton secretion is consistent with the postulation that SRIF may function at more than one site within the PC.
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PMID:Evidence for nongastrin-mediated somatostatin inhibition of parietal cell function. 287 98

A primary culture of chicken adenohypophyseal cells has been developed to study the regulation of growth hormone (GH) secretion. Following collagenase dispersion, cells were exposed for 2 hr to vehicle (control) or test agents. Human pancreatic (tumor) growth hormone-releasing factor (hpGRF) and rat hypothalamic growth hormone-releasing factor stimulated GH release to similar levels. GH release was increased by the presence of dibutyryl cyclic AMP. Thyrotropin-releasing hormone (TRH) alone did not influence GH release; however, TRH plus hpGRF together exerted a synergistic (greater than additive) effect, increasing GH release by 100 to 300% over the sum of the values for each secretagogue acting alone. These relationships between TRH and hpGRF were further examined in cultured cells exposed to secretagogues for two consecutive 2-hr incubations. TRH pretreatment enhanced subsequent hpGRF-stimulated GH release by about 80% over that obtained if no secretagogue was present during the first incubation. In other experiments, somatostatin (SRIF) alone did not alter GH secretion. However, SRIF reduced hpGRF-stimulated GH release to levels found in controls. Furthermore, GH release stimulated by the presence of both TRH and hpGRF was lowered to control values by SRIF. The results of these studies demonstrate that a primary culture of chicken adenohypophyseal cells is a useful model for the study of GH secretion. Indeed, these results suggest that TRH and hpGRF regulate GH secretion by mechanisms which are not identical.
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PMID:Growth hormone secretion from chicken adenohypophyseal cells in primary culture: effects of human pancreatic growth hormone-releasing factor, thyrotropin-releasing hormone, and somatostatin on growth hormone release. 288 41

We investigated the effects of cysteamine on the pancreatic islet hormones and found that pancreatic somatostatin contents depleted 60 min after the oral administration of cysteamine (300 mg/kg) to rats, yet the insulin and glucagon contents remained unchanged. When pancreatic islets isolated by collagenase digestion were incubated for 60 min in Krebs-Ringer bicarbonate buffer containing 0.1, 1, or 10 mM cysteamine, cysteamine dose-dependently decreased the somatostatin content, however, only a high concentration (10 mM) decreased the insulin level, and cysteamine exerted no effect on the glucagon content. The islet hormones (synthetic somatostatin-14, synthetic somatostatin-28, extracted pork insulin and extracted pork glucagon) were incubated for 60 min with cysteamine (0.1, 1, or 10 mM) and somatostatin-14 was found to be markedly decreased by 1 mM cysteamine. Pork insulin but not pork glucagon was dose-dependently decreased by 0.1-10 mM cysteamine. Cysteamine, 0.1-1 mM, did not interfere with the radio-immunoassay system for somatostatin or insulin, although 10 mM cysteamine did so. This compound exerted no effect on the radioimmunoassay system for glucagon. Our studies support earlier findings that cysteamine administered to experimental animals plays a role of relatively specific depletor of somatostatin. The possibility that the depletion of somatostatin is in part due to the remarkable sensitivity of the intracellular compartments of the D cells to the drug and in part due to the remarkable sensitivity of the molecular structure of somatostatin has to be considered.
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PMID:Mechanisms involved in the depleting effect of cysteamine on pancreatic somatostatin. 288 72

Somatostatin, somatotropin release-inhibiting factor (SRIF), is a regulatory peptide that has proved to directly inhibit parietal cell acid secretion. However, the therapeutic usefulness of SRIF has been limited by a brief plasma half-life. Several analogues of SRIF that are effective in suppressing acid secretion in vivo have been developed. This study was undertaken to compare the effects of SRIF and two analogues, SMS 201-995 and L-363,568, on in vitro acid secretion. We used isolated rabbit parietal cells prepared by collagenase digestion and counterflow elutriation. Acid secretion was assessed by the accumulation of 14C-aminopyrine within the cells. Two types of secretagogues were utilized: histamine (10(-6) mol/L), a membrane receptor agonist which acts by means of adenylate cyclase and cyclic AMP, and forskolin (10(-6) mol/L), a direct activator of adenylate cyclase. SRIF, SMS 201-995, and L-363,568 (10(-11) to 10(-7) mol/L) all significantly inhibited histamine-stimulated 14C-AP uptake (p less than 0.001). On a molar basis, SMS 201-995 was 10 times more potent and L-363,568 was 40 times more potent than SRIF. SRIF, SMS 201-995, and L-363,568 significantly inhibited forskolin-stimulated 14C-AP uptake (p less than 0.005). The inhibitory effects of SRIF and both analogues on forskolin-stimulated acid secretion was, however, significantly less than that observed with histamine (p less than 0.05). These results demonstrate increased in vitro potency of SRIF analogues compared with the native peptide. The data are consistent with the hypothesis that SRIF and its analogues function at more than one site within the parietal cell.
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PMID:Somatostatin analogue inhibition of isolated parietal cell secretion. 289 Dec 2

Growth hormone releasing factor (GHRF) was examined to determine whether it affects somatostatin (SRIF) release from cultured rat hypothalamic cells and fragments in vitro. The hypothalami of rat fetuses were collected on the 17th day of pregnancy under a dissection microscope. Thirty hypothalami were placed in phosphate buffered saline, and the cells were dispersed with 0.1% collagenase. The dispersed cells were cultured in Dulbecco's modified Eagle medium (DMEM) containing 10% horse serum and 2.5% fetal calf serum at 37 degrees C under 5% CO2 in air. On the 12th day of culture, the cells were washed with Krebs Ringer bicarbonate buffer containing glucose (KRBG), and then incubated with KRBG for 1 hour. The medium was replaced with KRBG alone (control) or KRBG containing test substances, and incubated for another hour. SRIF released into the medium was quantitated by RIA. The mean basal release of SRIF was 14.7 +/- 0.9 pg/dish/hour. One-tenth, 1, and 10nM hpGRF44 stimulated SRIF release by 1.4, 1.5, and 1.8 fold respectively in a dose-related manner. Ten nM ovine corticotropin releasing factor (o-CRF) also stimulated SRIF release by 2.3 fold. One, 10, and 100 nM hpGRF44, 10nM o-CRF, 10nM thyrotropin releasing hormone (TRH) and 60 mM K+ also stimulated SRIF release from rat hypothalamic fragments. Removal of Ca++ from the medium resulted in a decrease of basal release of SRIF. In Ca++ free medium, 10nM hpGRF44 failed to release SRIF. One-tenth nM hpGRF44, 10nM GnRH, and 10nM VIP have no effect on SRIF release statistically. The results of this study demonstrate that a high concentration of GHRF stimulates SRIF release from the hypothalamus in vitro, suggesting a possibility that GHRF may increase the release of SRIF from the median eminence and the hypothalamus in vivo under certain conditions.
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PMID:The stimulation of somatostatin release by hpGRF44 from rat hypothalamic cells and fragments in vitro. 289 40

It has previously been demonstrated that somatostatin (SRIF) directly inhibits parietal cell secretion. However, the significance of SRIF as a paracrine agent and mechanisms of local gastric SRIF release are not clear. Vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) are neuropeptides which have been localized in the gastric fundus and have been demonstrated to inhibit gastric acid secretion in vivo. The present study examines the hypothesis that CGRP and VIP act via the release of gastric fundic SRIF. The study utilized rabbit isolated gastric glands prepared by collagenase digestion. Glands were incubated alone, or with 10(-10)-10(-6) M CGRP or 10(-10)-10(-6) M VIP for 30 min. Supernatant SRIF was measured using a specific radioimmunoassay. Unstimulated SRIF release was 101 +/- 16 fmole/ml. CGRP (10(-7) and 10(-6) M) and VIP (10(-7) and 10(-6) M) resulted in significant SRIF release. The maximum release of SRIF by CGRP (506 +/- 113 fmole/ml) was significantly greater than that by VIP (293 +/- 33 fmole/ml) (P less than 0.05). However, both these concentrations of SRIF are comparable to the ID50 concentration (4.5 X 10(-10) M) for SRIF inhibition of acid secretion by isolated parietal cells as assessed by [14C]aminopyrine accumulation. These results are consistent with the hypothesis that CGRP and VIP inhibition of acid secretion may be mediated, at least in part, by the local release of SRIF from the gastric fundus. These data further support the significance of paracrine interactions in the modulation of cellular secretory function.
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PMID:Gastric somatostatin release: evidence for direct mediation by calcitonin gene-related peptide and vasoactive intestinal peptide. 289 38

The pineal indole melatonin suppresses the neonatal rat luteinizing hormone (LH) and follicle-stimulating hormone (FSH) responses to LH-releasing hormone (LHRH), as shown in previous studies from this laboratory. We show in this study that the melatonin inhibition is a selective effect and is not due to general inhibition of pituitary function. The effects of the indole on the responses to thyrotropin-releasing hormone (TRH) and somatostatin (SRIF) and on basal pituitary hormone secretion were examined with cells in culture. Neonatal rat anterior pituitary cells dissociated with collagenase and hyaluronidase were cultured overnight and distributed to 35-mm dishes at the time of use. For examination of melatonin effects on the response to releasing hormones, the cells were incubated for 3 h in control medium or medium containing LHRH (10-9-10-6 M), TRH (10-10-10-6 M), or SRIF (10-9-10-6 M), either alone or in the presence of melatonin (10-8 or 10-6 M). For examination of basal hormone secretion, the cells were incubated for 1.5, 3, 6, 15, or 24 h in either medium alone or medium containing melatonin (10-6 M). Medium and cell lysate concentrations of LH, FSH, thyroid-stimulating hormone (TSh), prolactin (PRL) and growth hormone (GH) were determined by double antibody RIA. As previously, melatonin (10-8 M) significantly suppressed LH and FSH release by all concentrations of LHRH. This concentration of the indole produced maximal suppression of both LH and FSH responses to LHRH. By contrast, melatonin at a 100-fold greater concentration (10-6 M) had no effect on TRH stimulation of TSH or PRL release or on SRIF inhibition of GH release. Similarly, melatonin had no effect on basal release of TSH, PRL, or GH at the times examined. These findings show that melatonin inhibition of the gonadotroph response to LHRH is a selective effect.
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PMID:Selectivity of melatonin pituitary inhibition for luteinizing hormone-releasing hormone. 612 68

We have developed a new short term in vitro system to examine hypothalamic somatostatin (SRIF) release. Hypothalamic cells were obtained from normal rats after trypsin or collagenase aided dispersion and released immuno-reactive (IR) SRIF which eluted in 3 molecular weight (MW) forms on gel chromatography. The smallest MW form, which constituted the major peak, co-eluted with synthetic cyclic 1-14 SRIF on gel and reverse phase high pressure liquid chromatography (HPLC). After 24 h in culture in medium containing heat inactivated fetal calf serum, cell viability was demonstrated by two techniques, (1) vital staining with trypan blue, and (2) incorporation of 32Pi into phospholipids. SRIF release was also studied at this time which was optimal in terms of responsivity of the cells to depolarizing stimuli. SRIF release increased in a time dependent manner, over 3 h. Membrane depolarization, induced either by potassium chloride 56 mM or ouabain (the Na+, K+-ATPase inhibitor) 10(-6) M or greater, markedly stimulated SRIF release. Incubation at 4 degrees C, or in the presence of EDTA 0.05 M or verapamil, the calcium channel blocker, 50 microM abolished these stimulatory effects. Glucose deprivation was induced by the addition of 2-deoxy-D-glucose (2-DG) to the experimental medium. 2-DG, at concentrations of up to 200 mg%, had no significant effect on SRIF release during incubation periods of up to 1 h.
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PMID:Somatostatin release from dispersed hypothalamic cells - effects of membrane depolarization, calcium and glucose deprivation. 613 93

We studied the release of immunoreactive somatostatin (IR-SRIF) from hypothalamic cells that were obtained from rats and dispersed with the aid of collagenase. Twenty-four hours after dispersion, cells were placed in a column supported by a matrix of preswollen Biogel P2 and perifused. Fractions were collected on ice and subsequently assayed for SRIF. SRIF release was stimulated markedly by potassium depolarization (KCl, 56 mM), by the Na+-K+-ATPase inhibitor ouabain (10(-4) M), and by dopamine at concentrations as low as 10(-11) M. The stimulatory effects of membrane depolarization were calcium dependent and were not observed in the absence of exogenous calcium in the perifusion medium or in the presence of EDTA (0.05 M). Metoclopramide, the dopamine antagonist, abolished the stimulatory effect of dopamine. In conclusion, release of IR-SRIF by dispersed rat hypothalamic cells can be studied in a simple perifusion apparatus. Release is stimulated by membrane depolarization in a calcium-dependent manner and by dopamine at physiological concentrations.
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PMID:Dopamine stimulates somatostatin release from perifused hypothalamic cells. 613 72

The goal of the study was to establish the age-related responses of cultured porcine pituitary cells to growth hormone-releasing factor (GRF) and(or) somatostatin (SRIF). A culture system for dispersed porcine pituitary cells was validated. Pituitaries from female pigs of various ages (90 or 110 d of gestation, newborn, 3, 6, or 24 mo old) were enzymatically dispersed with collagenase and neuraminidase, plated (200,000 cells/well), and cultured for 3 d. Plated cells were then subjected to a 4-h challenge with increasing concentrations of GRF (10(-11) to 10(-8) M), SRIF (10(-9) to 10(-6) M), or 10(-8) M of each peptide with increasing concentrations of the other. Culture media were collected and assayed for growth hormone (GH). Pituitaries were pooled so that there were four replicates per age, and treatments were assigned to quadruplicate wells. Concentrations of GH in control wells (basal GH) were maximal at 110 d of gestation and decreased thereafter (P < .01) with increasing age of swine. All peptide combinations affected the GH response (P < .05) at all ages studied, yet GRF was more potent than SRIF in eliciting a response. Age had an effect (P < .05) on the GH response to any of the treatments; younger pigs (90, 110 d of gestation and newborns) had a greater response (P < .05) than older pigs (3, 6, and 24 mo), whereas 6- and 24-mo-old pigs responded similarly in all cases (P > .1).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Validation of a culture system for porcine pituitary cells: effects of growth hormone-releasing factor and(or) somatostatin on growth hormone secretion. 809 10


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