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)

The hormonal responsiveness of plasma membrane-bound enzymes (Na-+-K-+)-ATPase and adenylate cyclase has been investigated in normal and regenerating rat liver. (Na-+-K-+)-ATPase basal activity is not affected by surgery and only slightly affected by partial hepatectomy; its response to epinephrine and cyclic AMP is decreased only 15 h after hepatectomy. Adenylate cyclase activity of plasma membranes from untreated animals is stimulated by parathyroid hormone and thyroxine; partial hepatectomy increased basal activity as well as the stimulation exerted by the aforementioned hormones, when glucagon and epinephrine sensitivity is essentially unaltered.
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PMID:Hormone responsiveness of plasma membrane-bound enzymes in normal and regenerating rat liver. 12 2

Studies were carried out to determine if the receptors for parathyroid hormone, calcitonin, and prostaglandin E1 could be differentiated in renal cortex. Slices of rabbit renal cortex were incubated in buffer containing theophylline for 1 hr and then in fresh buffer with and without hormone for an additional period of 15 to 30 min. Parathyroid hormone caused a marked increase in 3',5'-AMP in both the tissue and the reaction medium. The maximal increase in 3',5'-AMP in response to prostaglandin E1 was similar to that of parathyroid hormone in the tissue but significantly less in the medium. The maximal response to calcitonin was less in both the tissue and the medium. Addition of 200 mug/ml trypsin to the first incubation abolished the subsequent response to parathyroid hormone in both the tissue and the reaction medium but did not affect the basal concentration of 3',5'-AMP or the response to calcitonin or prostaglandin E1. Controls were carried out to show that the lack of response to parathyroid hormone could not be attributed to hydrolysis of the hormone by residual trypsin. Slices were also homogenized after preincubation with and without trypsin and assayed for adenylate cyclase activity. Incubation with trypsin markedly diminished the increase in enzyme activity in response to parathyroid hormone but did not alter the basal activity or the response to calcitonin or sodium fluoride. The response to prostaglandin E1 was significantly increased. Combinations of any two or the three hormones at maximal concentrations caused an additive increase in adenylate cyclase activity. The results indicate that the receptors for parathyroid hormone, calcitonin and prostaglandin E1 in renal cortex are separate and the receptor for parathyroid hormone can be selectively hydrolyzed by proteolytic digestion.
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PMID:Selective proteolysis of the receptor for parathyroid hormone in renal cortex. 16 81

It has been shown that both parathyroid hormone (PTH) and calcitonin (CT) increase the concentration of cyclic 3',5'-adenosine monophosphate (cyclic AMP) in skeletal tissue. Since these two hormones have opposing actions on bone resorption, it has been postulated that the cell types upon which the hormones act in skeletal tissue may be different. We have previously shown that osteoblasts and osteocytes contain adenylate cyclase responsive to both PTH and CT whereas the enzyme prepared from periosteum and marrow cells did not respond to either. To further examine the postulate, the effect of these hormones on the concentration of cyclic AMP was determined. Bovine PTH (5U/ml equal to 4.2 times 10-7M) significantly increased the concentration of cyclic AMP/mug DNA in periosteum, osteoblasts, and osteocytes but not in marrow cells. Porcine CT (0.5 U/ml equal to 8.0 mug/ml approximately equal to 3.0 times 10-6M) significantly increased the concentration of cyclic AMP/mug DNA in periosteum, osteoblasts, osteocytes, and marrow cells. Adenylate cyclase activity prepared from periosteum and marrow cells was re-examined using EGTA and DMSO to improve enzyme stability and activity. Wth these additions PTH (5 U/70 mul) increased activity of the preparation from periosteum, and CT (0.5 U/70 mul) increased activity from marrow cells and periosteum. These studies provide evidence that: 1) periosteum, osteoblasts, and osteocytes respond directly to both PTH and CT and 2) marrow cells respond to CT and not PTH.
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PMID:Cyclic 3', 5'-adenosine monophosphate levels in separated bone cells. 16 45

The effects of cholera toxin (CT) on the adenylate cyclase-adenosine 3',5'-cyclic monophosphate (cAMP) system(s) in renal cortex were examined using the isolated renal cortical tubules of rat. Unlike parathyroid hormone, catecholamines or prostaglandins, CT had no immediate effects on cAMP production by the tubules or on adenylate cyclase activity. However, after 30 min of incubation at 37 C, cAMP production by the tubules started to rise and reached a plateau between 60 and 90 min. This rise in cAMP production was not abolished by protein synthesis inhibitors (actinomycin D and cycloheximide) nor by the inhibitors of prostaglandin synthesis (acetyl-salicylate and indomethacin). Repeated washings of the tubules exposed to the toxin for five minutes at 0 or 37 C did not abolish the effect of CT to stimulate cAMP production. Assays of adenylate cyclase activity using homogenates prepared from isolated tubules which were incubated for 60 min with CT revealed an increase in the basal adenylate cyclase activity without any change in NaF-sensitive enzyme activity. It is concluded that CT binds to renal tubule cells rapidly, possibly through energy-independent process. CT stimulates adenylate cyclase activity and increases cAMP production by the renal tubule cells after a latent period of 30 min. The stimulatory effects of CT are not due to new protein synthesis or prostaglandin formation.
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PMID:Renal action of cholera toxin: II. Effects on adenylate cyclase-cyclic AMP system. 16 78

Glucagon activated adenylate cyclase in a homogenate of a pheochromocytoma over the concentration range 1 times 10 minus 8M to 1 times 10 minus 6M. Several other hormones including adrenocorticotropin, thyrotropin, parathyroid hormone and histamine were without effect. The tumor glucagon receptor was characterized and found to be similar in several ways to the glucagon receptor previously reported in normal tissue such as liver and heart. One, the receptor specifically bound 125-I-glucagon. Two, solubilization of the pheochromocytoma abolished glucagon-activation of the adenylate cyclase. Three, glucagon-responsiveness of the adenylate cyclase was partially restored by the addition of phosphatidylserine to the incubations. One major difference was observed between the glucagon receptor in tumor tissue and that in liver and heart, namely, a marked lability in 125-I-glucagon binding and adenylate cyclase activity. Within four days, despite storage in liquid nitrogen, 75% of the binding activity and all of the adenylate cyclase activity in the solubilized preparation were lost. The factor(s) responsible for this lability remains unidentified.
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PMID:Characterization of the glucagon receptor in a pheochromocytoma. 16 16

We have perfused isolated rat livers with hypocalcemic (4.4 mg 100 ml) Krebs-Ringer bicarbonate albumin buffer. After 15 min of perfusion, a substance appeared in the perfusate which decreased rat renal adenylate cyclase activation by parathyroid hormone (PTH). The material in the perfusate was purified greater than 50,000-fold by Bio-Gel P-10 chromatography. The purified antagonist decreased the activation of rat renal cortical adenylate cyclase by PTH, glucagon, and epinephrine 75 to 100%. Concentration response curves for each of the hormones indicated a noncompetitive interaction of the inhibitor with the hormone. The inhibition was not species-specific, as the activation of the parathyroid hormone-responsive adenylate cyclase in cat renal cortex was also abolished by the inhibitor from the perfused rat liver. The inhibitor is a peptide, Mr equal to similar to 1000, which is heat-stable, acid-stable, alkai-labile, and is destroyed by trypsin, leucine aminopeptidase, and elastase. It is not destroyed by phosphodiesterase, 5'-nucleotidase, alkaline phosphatase, neuraminidase, RNase, or phospholipase A. The inhibitor is not produced by isolated rat livers perfused with normocalcemic perfusion media. It is unclear whether the peptide is synthesized by the liver or whether it is a breakdown product of a larger peptide or protein in the liver. This is the first reported peptide inhibitor of adenylate cyclase.
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PMID:Isolation of a unique peptide inhibitor of hormone-responsive adenylate cyclase. 16 24

In potassium depletion, a possible alteration of the proximal tubular response to parathyroid hormone (PTH) was evaluated in rat kidney. 1) There were impairments of both phosphaturic and urinary cyclic AMP responses to PTH. The site of the impairment was further investigated by studying the PTH-dependent cycle AMP system in renal cortex. 2) There was a lesser increase of cyclic AMP concentration by PTH in potassium-depleted slices, indicating the lesser urinary cyclic AMP was due to the specific impairment of PTH-dependent cyclic AMP in the kidney. 3). The activation of adenylate cyclase by PTH was impaired , but phosphodiesterase activity was not affected by potassium depletion, indicating the impairment of cyclic AMP generation was due to inhibition of adenylate cyclase. 4) The phosphaturic response to dibutyryl cyclic AMP infusion was also significantly less in the potassium-depleted animals, indicating the step subsquent to the cyclic AMP generation is also impaired. All above results indicate that, in potassium depletion, the renal response to PTH is impaired, and the impairment is both within the step of cyclic AMP generation and after the cyclic AMP generation.
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PMID:Impaired renal response to parathyroid hormone in potassium depletion. 16 90

Parathyroid hormone, calcitonin, and prostaglandin E2 activate the adenylate cyclase-cyclic AMP system in fetal-rat calvaria. These agents presumably interact with the tissue at separate receptor sites. When calvaria were preincubated with trypsin, 500 mug/ml for 45 min, the subsequent increase in 3',5'-AMP in response to parathyroid hormone was markedly diminished, whereas the response to calcitonin and prostaglandin E2 were not altered significantly. The effect was attributable to an action of the enzyme on the tissue and not to hydrolysis of the hormone. Similarily, preincubation of calvaria with trypsin prior to homogenization and preparation of a crude plasma membrane fraction decreased PTH-sensitive adenylate-cyclase activity by 58% but did not alter the degree of stimulation of the enzyme in response to calcitonin, prostaglandin E2, or sodium fluoride. These studies support the hypothesis that the actions of parathyroid hormone and calcitonin on bone are mediated through distinct receptor sites, and the receptors for parathyroid hormone can be altered selectively with trypsin.
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PMID:Selective proteolysis of the receptor for parathyroid hormone in skeletal tissue. 16 56

Isolated kidney cortex tubules from starved rats have been used to study the actions of catecholamines on renal adenosine 3':5' monophosphate (Ado-3':5'-P) levels and gluconeogenesis. In accordance with previous workers, norepinephrine was found to increase glucose formation from lactate and pyruvate and to a smaller degree from malate, succinate, fumarate and glutamine. The stimulatory effect of 0.5 muM norepinephrine was additive to that of 0.1 mM Ado-3':5-P, indicating an Ado-3':5'-P-independent mechanism of catecholamine action. The effects of parathyroid hormone and oleate on gluconeogenesis were also additive to that of norepinephrine. A comparative study of the actions of different catecholamine derivatives revealed that gluconeogenesis was stimulated in parallel to the alpha-adrenergic potency of the hormones, whereas Ado-3':5'-P levels were increased according to the known beta-stimulatory potency of the agents. Although isoproterenol was by far the most effective in raising Ado-3':5'-P levels, it was without effect on glucose formation from pyruvate, when added at 0.1 muM. At the same concentration, phenylephrine, which had no effect on Ado-3':5'-P levels, was the best stimulator of gluconeogenesis. The alpha-receptor blocking agent phentolamine inhibited the stimulatory effect of catecholamines on gluconeogenesis with a 50 times higher potency than propranolol, a beta-blocking agent. The fact that the stimulatory effect of Ado-3':5'-P was also blocked by propranolol, indicated an unspecific mechanism of action of this substance. The results indicate that the stimulatory effect of catecholamines on renal gluconeogenesis are mediated by an alpha-receptor and that they are independent from the stimulation of renal adenyl cyclase by these agents.
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PMID:Metabolism of isolated kidney tubules. Independent actions of catecholamines on renal cyclic adenosine 3':5'-monophosphate levels and gluconeogenesis. 17 87

Purification of pork renal cortex membranes yielded a particulate adenylate cyclase retaining good sensitivity to stimulation by parathyroid hormone and glucagon and a modest but significant response to porcine calcitonin. Treatment of this partially purified membrane fraction with 0.5% Lubrol PX and 5 mM NaF released adenylate cyclase activity into a fraction which was not sedimented by centrifugation for 20 min at 37,000 X g or for 2 hours at 100,000 X g and passed through a Millipore filter (0.22 mum pore). This solubilized adenylate cyclase was stimulated by porcine calcitonin and NaF but not by parathyroid hormone or glucagon. On gel filtration (Sephadex G-200) in the presence of 1mM dithiothreitol and 5mM NaF, the major portion of the adenylate cyclase activity eluted with the void volume of the column and showed 2.0-fold stimulation with 10 muM calcitonin. Binding of 125I-labeled porcine calcitonin was demonstrated in the 37,000 X g and the 100,000 X g supernatants. From 74 to 86% of the observed binding could be blocked by the addition of unlabeled porcine calcitonin to the reaction mixture. Addition of salmon calcitonin, parathyroid hormone, or glucagon blocked only 12 to 18% of the binding. The dose-response curves for inhibition of binding of iodinated calcitonin by unlabeled calcitonin and the activation of adenylate cyclase by the hormone each showed 50% maximal effect at a concentration between 4.5 and 8 muM porcine calcitonin and maximal effect at a concentration between 33 and 66 muM porcine calcitonin.
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PMID:Solubilization of calcitonin-responsive renal cortical adenylate cyclase. 17 Feb 64


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