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 beta-adrenoceptor density and the activities of adenylate cyclase and cyclic AMP phosphodiesterase were examined to compare AH13 cells having lower beta-adrenergic responsiveness with other rat ascites hepatoma cells and normal rat liver cells. Normal rat liver cells used were cultured for 24 hr after the collagenase digestion of liver. The density of binding sites of 3H-dihydroalprenolol in AH13 cell plasma membrane was very similar to the density in AH44 and normal liver cell membrane, but that in AH130 cell plasma membrane was about 10-fold greater than those in the other three cell lines. The activity of cyclic AMP phosphodiesterase was about 2.5- to 7-fold higher in hepatoma cells than in rat liver cells, but this enzyme activity of AH13 cells was not especially high among the hepatoma cells examined. The basal adenylate cyclase activity was lower in AH44 cells, but was higher in AH13 and AH130 cells than in rat liver cells. However, adenylate cyclase of AH13 cells was hardly activated by isoproterenol, while the enzyme of the other cells was activated 3- to 5-fold. On the other hand, adenylate cyclase of each cell line including AH13 was activated 4- to 14-fold by NaF. From these results, it is suggested that AH13 cells can hardly produce cyclic AMP by the beta-adrenergic stimulation because of the disordered interaction of beta-adrenoceptors with adenylate cyclase.
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PMID:Studies on responsiveness of hepatoma cells to catecholamines. I. Lack of beta-adrenergic responsiveness in rat ascites hepatoma AH13 cells. 609 61

Free cells isolated from adult rat heart by the collagenase method were maintained in culture up to 21 h with or without an islet-activating protein (IAP) that had been purified from the culture medium of Bordetella pertussis. Short-term stimulation of beta-adrenergic or glucagon receptors in these cultured cells caused more accumulation of cAMP in cells precultured with IAP (IAP-treated) than in nontreated cells, although there was no significant difference in the baseline (non-stimulated) content of cAMP between these cells. Stimulation of muscarinic cholinergic or adenosine R-site receptors caused a marked inhibition of cAMP accumulation in nontreated cells in either the presence or absence of a beta-agonist (or glucagon); no such inhibition was essentially observed in IAP-treated cells. These actions of IAP developed gradually and were dose-dependent with the half-maximal concentration of approximately 80 ng/ml in culture. It is concluded that IAP may exert its unique influence on the heart cell membrane causing profound modification of the coupling mechanism involved in the receptor-mediated activation or inhibition of adenylate cyclase. This action of IAP differs clearly from that of cholera toxin which activates adenylate cyclase rather independently of the receptor functions in heart cells.
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PMID:Modification by islet-activating protein of receptor-mediated regulation of cyclic AMP accumulation in isolated rat heart cells. 616 42

Capillaries isolated by collagenase digestion of hamster epididymal fat pads were used to examine the properties of endothelial adenylate cyclase and cyclic nucleotide phosphodiesterase. Adenylate cyclase activity in capillary homogenates was increased by 10 microM GTP or 100 microM isoproterenol. Lower concentrations of the catecholamine and 5.7 microM prostaglandin E1 did not stimulate endothelial adenylate cyclase activity unless GTP was included in the assay system. The effects of isoproterenol on capillary adenylate cyclase activity were blocked by propranolol, but were not affected by phentolamine. Phosphodiesterase activity in endothelial homogenates showed anomalous kinetic behavior with either cyclic AMP or cyclic GMP as the enzyme substrate. At substrate concentrations below 1 microM, capillary phosphodiesterase activity hydrolyzed cyclic GMP 2-6 times faster than cyclic AMP. However, at high substrate levels, e.g., 100 microM, cyclic AMP and cyclic GMP were degraded at similar rates. Hydrolysis of 1 microM cyclic AMP by capillary homogenates was stimulated by 0.1 and 1 microM cyclic GMP. Caffeine, 1-methyl-3-isobutylxanthine, papaverine and dipyridamole SQ 20009 were effective inhibitors of capillary phosphodiesterase activity. In contrast, imidazole enhanced the activity of the enzyme. The presence of adenylate cyclase and phosphodiesterase activities in hamster isolated capillaries is consistent with a role for cyclic AMP in the regulation of endothelial function. Moreover, the experiments described here indicate that hamster isolated capillaries are useful model systems for studying the metabolism of vascular endothelium.
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PMID:Properties of adenylate cyclase and cyclic nucleotide phosphodiesterase in hamster isolated capillary preparations. 624 1

The structural requirements for the inhibition of net bone collagen synthesis by parathyroid hormone (PTH) in vitro have been examined by study of the effects of selected fragments and analogs of bovine PTH (bPTH) upon the incorporation of [3H]proline into collagenase-digestible and -nondigestible proteins by neonatal mouse calvarial bone in organ culture. At concentrations of 10(-10)-10(-7) M, the amino-terminal fragment bPTH-(1-34) was found to be as potent as intact bPTH in the specific suppression of net bone collagen synthesis after 24 h in culture. The synthetic fragments bPTH-(1-30), bPTH-(1-28), and bPTH-(3-34) were approximately 3%, 1%, and 0.2% as active, respectively, as bPTH-(1-34), in good agreement with previous estimates of the relative potencies of these hormonal fragments on bone resorption in vitro and in vivo and on adenylate cyclase activation in and receptor binding to isolated renal membranes. The amino-terminal analog [Ser1]bPTH-(1-34) displayed no reduction in biological activity compared with bPTH-(1-34), as previously found for bone resorption in vivo. The overall results with this assay system indicate a minimum sequence for biological activity that extends from residues 3-28 of intact bPTH, which is consistent with similar estimates in other test systems and emphasizes the importance of the aminoterminus of the hormone in the expression of its biological effects on bone formation as well as resorption. Moreover, these findings support the potential usefulness of the mouse calvarial culture system in predicting the skeletal activity in vivo of new synthetic analogs of PTH.
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PMID:Bone collagen synthesis in vitro: structure/activity relations among parathyroid hormone fragments and analogs. 625 80

A homogeneous population of single cells from the thick ascending limb of Henle's loop (TALH) has been isolated from the rabbit kidney medulla. A total medullary cell suspension was prepared by a series of collagenase, hyaluronidase, and trypsin digestions and separated on a Ficoll gradient (2.6-30.7% wt/wt). Morphologically, the cells isolated from the TALH were homogeneous and showed polarity within their plasma membrane structure, with a few blunt microvilli on their apical surface and deep infoldings of the basal-lateral membrane. Biochemically, the TALH cells were highly enriched in calcitonin-sensitive adenylate cyclase and Na, K-ATPase. Alkaline phosphatase and arginine vasopressin-sensitive adenylate cyclase, highly concentrated in proximal tubule and collecting duct, were present only in low concentrations in the TALH cells. Additionally, furosemide, a diuretic inhibiting sodium chloride transport in the TALH in vivo, inhibited oxygen consumption of the TALH cells in a dose-dependent manner. The TALH cells were viable, as judged by morphological appearance, trypan blue exclusion, the response of oxygen consumption to 2,4-dinitrophenol, succinate and ouabain, and the cellular Na, K and ATP levels.
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PMID:Separation of renal medullary cells: isolation of cells from the thick ascending limb of Henle's loop. 625 27

In attempting to understand the causes of the hyperglycaemia observed in aging populations and to determine the mechanism(s) for the diminished in vitro insulin release from islets of Langerhans of older rats, the adenylate cyclase-cyclic AMP system was studied in isolated islets from 12 month old and 2 1/2 month old (control) male rats to determine its role in this altered insulin secretion. Islets of Langerhans were isolated by collagenase digestion and then either incubated in the presence of low or high concentrations of glucose for studies of insulin release or were sonicated and assayed for determinations of activities of adenylate cyclase and phosphodiesterase. Insulin release was identical from islets of 12 month old and 2 1/2 month old rats to 2.8 mM D-glucose, while in the presence of 16.7 mM D-glucose, insulin release was decreased by 33% (P less than 0.02) from islets of the older animals. Adenylate cyclase activity was diminished by 60% (P less than 0.005) from the 12 month old rats as compared with islets from the 2 1/2 month old controls, while low Km phosphodiesterase activity was similar in islets from both groups of animals. From these studies it appears that the adenylate cyclase-cyclic AMP system may play a role in the altered insulin release from islets of aging rats.
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PMID:Role of the adenylate cyclase system in altered insulin release from islets of Langerhans of aging rats. 625 70

Hormone-dependent adenylate cyclase activity was measured separately in the different nephron portions by combining the microdissection of collagenase-treated rabbit kidneys and the use of a single tubule enzyme microassay. The results obtained in the rabbit for vasopressin, parathyroid hormone, calcitonin, and isoproterenol are given and discussed. Each hormone stimulated adenylate cyclase activity in several well-localized segments of tubule according to a highly specific and reproducible pattern. Sharp transitions were generally noted between responsive and unresponsive nephron portions. In the rat kidney, the functional segmentation of the distal convoluted tubule was not as clearly delineated as in the rabbit kidney. Various nephron segments of the rat kidney were observed to contain glucagon-sensitive adenylate cyclase activity. When the results obtained for vasopressin are compared in rabbit, rat, mouse, and human kidneys, species differences are noted with respect to the responsiveness to arginine vasopressin in the medullary portion of thick ascending limbs of Henle's loops. It is concluded that biochemical approaches can be used as a means of investigating problems dealing with kidney physiology very near the cell level.
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PMID:Sites of hormone action in the mammalian nephron. 625 51

Supernatant fluids from the cultures of bone marrow cells from 10 of 12 patients with multiple myeloma (MM) caused bone resorption in organ cultures of fetal rat calvaria. In four patients, the marrow cells were cultured with and without indomethacin (1 muM). The supernatant fluids from indomethacintreated marrow cultures caused significantly less bone resorption than supernatant fluids of cell cultures without indomethacin. This inhibition of release of bone resorbing factor(s) by myeloma cultures is similar to the previously observed indomethacin-induced inhibition of osteoclast-activating factor (OAF) production by activated human leukocytes. None of the MM supernatants had any effect on cyclic (c)AMP accumulation in resorbing bone in vitro. Four separate preparations of partially purified OAF obtained from phytohemagglutinin-stimulated peripheral human leukocytes were tested for their ability (a) to cause bone resorption in organ cultures of fetal rat and neonatal mouse calvaria and (b) to cause accumulation of cAMP in rat and mouse skeletal tissue in vitro. Those dilutions of OAF that caused bone resorption had no effect on accumulation of cAMP in rat or mouse calvaria incubated in vitro. In addition, no stimulation of adenylate cyclase activity in membranes prepared from fetal rat calvaria could be found. Bone cell populations isolated by sequential collagenase digestion of fetal rat calvaria also showed no cAMP response to these dilutions of OAF. Parathyroid hormone caused a clear response in all three systems. Furthermore, no cAMP response to OAF was observed in calvaria in the presence of cholera toxin (1 mug/ml) and isobutyl-methylxanthine (0.3 mM). These observations demonstrate that (a) supernatant fluids from MM marrow cultures stimulate bone resorption but do not increase cAMP accumulation in vitro; (b) indomethacin interferes with the release of bone resorbing factors by MM bone marrow cultures suggesting that this process requires prostaglandins; and (c) Sephadex G100 or G75 purified OAF does not stimulate adenylate cyclase or increase cAMP accumulation at equivalent bone resorbing concentrations in rat and mouse skeletal tissue. The resorptive action of MM culture fluids is similar to that of partially purified OAF from activated cultured leukocytes, but different from those of other bone resorbing factors, parathyroid hormone and prostaglandin E(2), which stimulate cAMP production in skeletal tissue.
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PMID:Observations on the mechanism of bone resorption induced by multiple myeloma marrow culture fluids and partially purified osteoclast-activating factor. 626 78

Effects on Ca2+ transport of parathyroid hormone (PTH) and N6,O2'-dibutyryl adenosine 3',5'-cyclic monophosphate (DB-cAMP) were examined in the rabbit distal nephron segments including the cortical thick ascending limb of Henle's loop (CAL), the connecting tubule (CNT) and the cortical collecting tubule (CCT) by the in vitro perfusion technique. When PTH (10(-8) mol . l-1) was added to the bath, efflux of Ca2+ (pmol . mm-1 . min-1) was increased from 6.29 +/- 1.46 to 7.96 +/- 1.66 (P less than 0.02) in the CAL, and from 8.55 +/- 1.30 to 13.73 +/- 1.24 (P less than 0.001) in the CNT, respectively, without changes in influx of Ca2+. The effect of PTH on Ca2+ transport in the CAL, however, was abolished when phosphate concentration in the medium was reduced from 3.0 to 1.0 mmol . l-1. When DB-cAMP (10(-3) mol . l-1) was added to the bath, efflux of Ca2+ was also increased from 7.01 +/- 0.83 to 9.40 +/- 0.82 (P less than 0.05) in the CAL, and from 13.11 +/- 0.89 to 19.74 +/- 0.52 (P less than 0.005) in the CNT, respectively. By contrast, neither PTH nor DB-cAMP affected efflux of Ca2+ in the CCT. PTH did not affected the transepithelial voltage either in the CAL or in the CNT. But in the CNT, DB-cAMP decreased the voltage from -14.1 to -9.4 mV. The response of adenylate cyclase activity to PTH in the collagenase treated isolated nephron segments was also examined. Significant increases in adenylase cyclase activity were observed in the CAL as well as in the CNT with 10(-6) mol . l-1 PTH. These data indicate that PTH stimulates Ca2+ transport across the CNT probably via activation of the adenylate cyclase-cyclic AMP system. The hormone may also stimulate Ca2+ transport across the CAL in a special condition where plasma phosphate concentration is elevated.
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PMID:Effects of parathyroid hormone and N6,O2'-dibutyryl cyclic AMP on Ca2+ transport across the rabbit distal nephron segments perfused in vitro. 626 87

Kupffer cells exposed to bacterial lipopolysaccharide in vitro synthesized collagenase and released the major portion of it into the extracellular space while the intracellular level of enzyme was not altered significantly. Cycloheximide prevented the appearance of collagenase in the medium indicating de novo synthesis. Indomethacin, an inhibitor of cyclooxygenase, also blocked collagenase synthesis. In line with this observation. Kupffer cells were found to synthesize substantial amounts of prostaglandin E2 when exposed to lipopolysaccharide; concomitantly, cellular cAMP levels were increased. Indomethacin was shown to abolish the stimulated cAMP formation. Addition to the culture medium of cAMP or dibutyryladenosine 3', 5'-monophosphate as well as of prostaglandin E2 or, to a lesser extent, prostaglandin E1 allowed indomethacin-inhibited cells to resume the production of collagenase. It is proposed that in rat Kupffer cells lipopolysaccharide-elicited collagenase synthesis and excretion is mediated sequentially by stimulated production of prostaglandin E2, enhanced adenylate cyclase activity and increased intracellular cAMP levels.
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PMID:Involvement of prostaglandin E and adenosine 3', 5'-monophosphate in lipopolysaccharide-stimulated collagenase release by rat Kupffer cells. 628 7


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