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:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cells were isolated by use of collagenase, EDTA and pronase form human gastric mucosa obtained at peptic ulcer surgery (n = 61) or at Whipple's operations (n = 6). Enriched parietal cell fractions were prepared by isopycnic centrifugation with Percoll. H+ production, intracellular instrinsic factor and histamine content were maximal in the low density fraction containing 75% parietal cells and--among other nonparietal cell types--mast cells. H+ production, intrinsic factor secretion and adenylate cyclase-activity responded to histamine stimulation in a concentration dependent manner. Response was blocked by histamine H2 receptor antagonists (rantidine, famotidine). Dibutyryl cAMP and the phosphodiesterase inhibitor IMX were the most powerful stimuli whereas carbachol, hexoprenaline and pentagastrin were less effective. Prostaglandin E2 and 6-keto-PGF2 alpha occurred in the highest concentrations in the low density cell fraction. PG production increased linearly for 15 min and seemed to be influenced by the intracellular calcium level.
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PMID:[Isolated human gastric mucosa cells--studies on physiologic and pharmacologic regulatory mechanisms]. 286 82

The responsiveness to three beta-adrenergic agonists, isoproterenol (IPN), epinephrine (Epi) and norepinephrine (NE) in AH13O cells was examined compared with that in normal rat liver cells which were cultured for 24 hr after collagenase digestion. As regards to the activation of adenylate cyclase in the cell homogenates, the relative affinity of the three agonists was in order of IPN greater than NE greater than Epi in AH130 cells and IPN greater than Epi greater than NE in cultured normal liver cells. While the efficacies of the three agonists were similar in cultured liver cells, those of NE and Epi were markedly lower than that of IPN in AH13O cells and were increased to the similar level of IPN by pretreatment with phentolamine, but not with prazosin. Clonidine inhibited the activation of adenylate cyclase by IPN in AH13O cells. When cells were preincubated with islet-activating protein (IAP), the activity of adenylate cyclase in the presence or absence of agonist in both cell lines increased. In IAP-treated AH13O cells, the efficacies of NE and Epi became close to that of IPN. Adenylate cyclase in IAP-treated AH13O cells was activated by GTP in a dose-dependent manner, but that in IAP-treated cultured liver cells was not. In the presence of IPN, biphasic (activatory and inhibitory) effects of GTP on the cyclase were observed, and the inhibitory phase was eliminated by the IAP-treatment in both cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Studies on responsiveness of hepatoma cells to catecholamines. III. Difference between the receptor-adenylate cyclase regulating systems in AH130 cells and cultured normal rat liver cells. 287 59

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

Functional gastrin-containing tumor cells (GT cells) have been maintained in short-term culture on microporous membranes, and their response to selected agents has been determined. After dispersion of gastrinoma by collagenase-DNAase digestion coupled with mechanical disruption, dispersed cells were depleted in stromal material by selective attachment to a plastic substrate, then cultured for 72 hours on porous cellulose membranes. Cultures contained 68 +/- 5% GT cells with a viability of 92 +/- 2%. Secretin stimulated the rate of gastrin release from cultured GT cells in both a time- and a dose-dependent fashion. To examine the possible involvement of adenylate cyclase- and protein kinase C-mediated mechanisms in regulating gastrin release from the neoplastic GT cells, we evaluated the effects of 8-bromoadenosine 3':5'-cyclic monophosphate (8-BrcAMP; 10(-4) - 10(-2) mol/L), the diterpene forskolin (10(-5) mol/L), 12-0-tetradencanoylphorobol 13-acetate (TPA; 10(-8) - 10(-6) mol/L), and 4 alpha-phorbol 12,13-didecanoate (4 alpha PDD; 10(-8) - 10(-6) mol/L) on gastrin release. Among all compounds tested, 8-BrcAMP (10(-2) mol/L) was the most potent, stimulating the rate of gastrin release 263% above basal. Both 8-BrcAMP and TPA stimulated gastrin release in a dose-dependent fashion. The biologically inactive phorbol ester, 4 alpha PDD, was without effect at all concentrations. Somatostatin (10(-8) - 10(-6) mol/L) inhibited 8-BrcAMP-stimulated gastrin release in a dose-dependent fashion to a maximum of 75%.
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PMID:Control of gastrin release in cultured gastrinoma-derived G cells. 289 16

The influence of follicular maturation on progesterone production by collagenase-dispersed hen granulosa cells was measured in short-term incubations. Granulosa cells of the largest follicle (F1) produced up to ten times more progesterone than cells from smaller follicles (F3-F5), not only in response to luteinizing hormone (LH), but also when stimulated by exogenous cyclic AMP or forskolin, both of which raise intracellular cyclic AMP levels by nonreceptor-mediated mechanisms. Moreover, when granulosa cell progesterone synthesis was stimulated by incorporating 25-hydroxy-cholesterol into the incubation medium, an identical pattern was obtained. This could be attributed to a corresponding increase in the specific activity of the mitochondrial cholesterol side-chain cleavage enzyme (20,22 desmolase). An increase in the apparent Vmax was observed without a change in the apparent Km values. Pregnenolone substrate at concentrations which raised progesterone production to levels similar to those observed in response to LH stimulation was utilized equally by granulosa cells of mature and developing follicles. However, at high pregnenolone concentrations, granulosa cells of mature follicles converted significantly more of the precursor to progesterone. Assay of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) showed that the enzyme has two Kms: a low Km present in cells of both mature and developing follicles, and a high Km found only in granulosa cells of more mature follicles. It is concluded that LH-promoted progesterone synthesis in granulosa cells of developing chicken follicles is restricted not so much by the availability of receptors and the competence of the adenylate cyclase/cyclic AMP system, but by the activity of key enzymes, principally the cholesterol-20,22 desmolase.
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PMID:Influence of follicular maturation on luteinizing hormone-, cyclic 3',5'-adenosine monophosphate-, forskolin- and cholesterol-stimulated progesterone production in hen granulosa cells. 298 34

It is well recognized that serotonin stimulates aldosterone production by the adrenal glands. To investigate the possible roles of serotonin type 1 and 2 receptors in the regulation of aldosterone production, we examined the effects of cyproheptadine (a serotonin antagonist that inhibits both type 1 and 2 receptors) and ketanserin (a serotonin type 2 selective antagonist) on aldosterone and cAMP production in collagenase dispersed rat adrenal capsular cells. Serotonin, ranging in concentration from 10(-9) to 10(-3) M, significantly increased aldosterone production in a dose-dependent fashion after 2 h of incubation at 37 degrees C. Cyproheptadine and ketanserin showed comparable inhibitory effects on basal aldosterone production. These serotonin antagonists preferentially inhibited serotonin-induced aldosterone production. Serotonin significantly increased cAMP production at a dose of 10(-6) M. Both cyproheptadine and ketanserin significantly decreased basal cAMP production at doses of 10(-5) M. These serotonin antagonists preferentially inhibited serotonin-stimulated cAMP production. These results suggest that adrenal serotonin type 2 receptors may be coupled with adenylate cyclase activity and that these receptors are involved in the regulation of aldosterone production. Whether serotonin plays an important role in the regulation of aldosterone secretion in vivo remains to be elucidated.
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PMID:Role of serotonin type 2 receptors in regulation of aldosterone production. 299 85

Although Ismail-Beigi and Edelman demonstrated in 1971 that thyroid hormones control the activity of Na-K-ATPase in the mammalian kidney, the actual site of this regulation inside the organ was not located. We therefore decided to study the relationship between thyroid hormones and Na-K-ATPase activity in individual nephron segments obtained by microdissection of collagenase-treated rabbit kidneys. For this purpose, the changes in the activity and number of catalytic sites of Na-K-ATPase in response to thyroidectomy or triiodothyronine administration were examined. Eight to 12 days after thyroidectomy, Na-K-ATPase activity had dropped by 40 to 80% in the convoluted and straight portions of the proximal tubules, and in the cortical and outer medullary collecting tubules, but not in the thick ascending limbs of Henle's loops or distal convoluted tubules. The apparent number of catalytic sites for Na-K-ATPase, as measured by specific binding of 3H-ouabain, decreased in parallel with Na-K-ATPase activity, and therefore this enzyme's specific activity was not altered. Fourty eight hours after injection of thyroidectomized animals with a single dose of either 100 or 500 micrograms/kg triiodothyronine, Na-K-ATPase activity in target segments was restored to the level measured in control animals. These effects of thyroid hormone were specific for Na-K-ATPase, since the activity of adenylate cyclase, another marker of the basolateral membrane, was not altered by thyroidectomy. The results obtained indicate that triiodothyronine controls Na-K-ATPase activity in specific nephron segments, by altering the number of this enzyme's catalytic sites.
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PMID:Sites of thyroid hormone action on Na-K-ATPase along the rabbit nephron. 299 94

The role of phospholipids in the maintenance of beta-adrenoceptor function was investigated in isolated canine myocytes prepared from eight adult mongrel dogs by using collagenase. The characteristics of beta-adrenoceptors were assessed by determining the number and the affinity of receptors by a radioactive ligand binding assay using 125I-iodocyanopindolol. The increase in cyclic AMP content induced by isoproterenol or forskolin was also determined by radioimmunoassay with or without pretreatment with phospholipase (PLase) A2. The amount of free fatty acids released from isolated myocytes by PLase A2 was measured by high-performance liquid chromatography. PLase induced a significant decrease in the number of beta-adrenoceptors but did not affect their affinity. Although the isoproterenol-stimulated increase in cyclic AMP was significantly inhibited by the pretreatment with PLase A2, the forskolin-stimulated increase was not affected. Responsive accumulation of cyclic AMP to isoproterenol was much more impaired than the decrease in beta-adrenoceptor number. These results indicate that PLase A2 deteriorates the function of the adenylate cyclase system linked-beta-adrenoceptor, and suggest that PLase A2 affects both beta-adrenoceptors and the coupling of beta-adrenoceptors with adenylate cyclase.
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PMID:The effects of phospholipase A2 on beta adrenoceptor function in isolated cardiac cells. 300 82

Rat renal medullary tubular cells, prepared by collagenase dispersion and hypotonic lysis, were introduced in Teflon chambers for superfusion. Prostaglandin (PG) E2 and cyclic adenosine 5'-monophosphate (cAMP) production was measured in the effluent. Arginine vasopressin (AVP) but not 1-deamino-8-D-arginine vasopressin (dDAVP) (10(-10)-10(-6) M), induced a dose-dependent increase in PGE2 synthesis, whereas AVP and dDAVP produced a similar dose-dependent increase in cAMP synthesis. The Ca2+ ionophore A23187 (10(-6) M) stimulated PGE2 synthesis but not cAMP production. In contrast, forskolin (10(-5) M) stimulated cAMP synthesis without affecting PGE2 generation. The pressor antagonists dEt2AVP and d(CH2)5Tyr(Me)AVP (10(-5) M) completely inhibited the PGE2 response to 10(-8) M AVP, whereas d(CH2)5-D-LeuVAVP (10(-6) M), a mixed pressor-antidiuretic antagonist, inhibited incompletely. dEt2AVP did not significantly affect cAMP synthesis in response to 10(-8) M AVP, whereas d(CH2)5-D-LeuVAVP, and unexpectedly also d(CH2)5Tyr(Me)AVP, were inhibitory. dPTyr(Me)AVP (10(-7) M), a pressor antagonist, had an unexpectedly high cAMP-stimulating capacity. In Ca2+-free media containing EGTA, the PGE2 response to AVP and A23187 was inhibited. Nifedipine (10(-6) M) did not significantly inhibit the AVP-stimulated PGE2 production. Thus AVP-stimulated PGE2 synthesis is linked to a V1-receptor in renal medullary tubular cells and occurs independently to the activation of adenylate cyclase through a V2-receptor.
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PMID:Prostaglandin E2 and cyclic AMP response to vasopressin in renal medullary tubular cells. 301 60

The acute antigonadotrophic action of prostaglandin F2 alpha (PGF2 alpha) was examined in dispersed luteal cell preparations from immature superluteinized rat ovaries. Cell suspensions prepared by collagenase digestion and purification over a Percoll density gradient were incubated for 1 h in Eagle's minimum essential medium in the presence and/or absence of LH, PGF2 alpha, N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate (dbcAMP) and forskolin. Medium was assayed for total progesterone and adenosine 3',5'-cyclic monophosphate (cAMP). Luteal cell preparations showed typical steroidogenic (progesterone) responses to LH, mimicked by both dbcAMP and forskolin. Whilst the threshold LH dose to increase cAMP synthesis was greater than that for progesterone (100 micrograms/l compared with 1 microgram/l), 24 mumol forskolin/l was the threshold dose for both cAMP and progesterone responses. Furthermore, combined doses of LH and forskolin synergistically raised cAMP yet produced less than additive increases in progesterone. Similarly, combinations of dbcAMP plus forskolin produced less than additive progesterone increases. These data suggest that forskolin may not act as a simple mimic of LH. Prostaglandin F2 alpha dose-dependently inhibited forskolin-induced cAMP and progesterone synthesis and also inhibited progesterone synthesis induced by dbcAMP. These data suggest that the antigonadotrophic effect of PGF2 alpha has more than one locus of action, i.e. it both inhibits an adenylate cyclase event associated with cAMP generation and blunts the cellular response to cAMP. The present uncertainty over the exact locus of forskolin's action within the adenylate cyclase complex limits further delineation of the inhibitory action of PGF2 alpha on LH-responsive adenylate cyclase.
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PMID:Prostaglandin F2 alpha-induced functional luteolysis: interactions of LH, prostaglandin F2 alpha and forskolin in cyclic AMP and progesterone synthesis in isolated rat luteal cells. 302 26


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