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)

1,25(OH)2D3 induced a dose-dependent increase of alkaline phosphatase activity in primary cultures of fetal rat osteoblast-like cells. A slight decrease in final DNA content was found in densely seeded cultures and at 10(-8) M 1,25(OH)2D3 only. Furthermore, 1,25(OH)2D3 treatment resulted in an attenuation of the cAMP response to PTH without an effect on the EC50 of PTH. On the other hand no change of the cAMP response to forskolin was observed. Forskolin partly restored the decline in the PTH-stimulated adenylate cyclase activity. The results indicate that physiological concentrations of 1,25(OH)2D3 have a stimulatory effect on the alkaline phosphatase of osteoblast-like cells and decrease the responsiveness of these cultures to PTH. We propose that the site of action of 1,25(OH)2D3 in the adenylate cyclase system is either at the level of the regulatory unit or on the interaction of the regulatory with the catalytic unit.
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PMID:The effects of 1,25-dihydroxyvitamin D3 on growth, alkaline phosphatase and adenylate cyclase of rat osteoblast-like cells. 284 88

Guanylate cyclase in rat cerebellum was investigated on the light microscopical level with guanylyl imidodiphosphate as substrate. Several attempts for activation of enzymatic activity and delimitation to other enzymes were made by sodium azide, aminophylline, sodium fluoride and dithioerythrole. The localization was similar but less strong compared to adenylate cyclase (Poeggel and Luppa 1984) and differs in behaviour to the above mentioned substances. Nucleotide pyrophosphatases seem to play an unimportant role in guanylyl imidodiphosphate conversion, while alkaline phosphatase is possibly of more importance. A light microscopical demonstration of guanylate cyclase by its enzymatic activity must be considered with caution. Main reasons are the low activity and therefore the great importance of interfering enzymes with high activities.
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PMID:Attempts for light microscopical demonstration of guanylate cyclase activity in rat cerebellum. 287 7

Cell fractionation studies have been performed, in order to obtain insight into the subcellular distribution of Dictyostelium adenylate cyclase and guanylate cyclase and also to provide a starting point for further study and isolation of these enzymes and their regulatory components. Adenylate cyclase and cAMP receptors were found in the same membrane fractions, but were distributed different from the plasma membrane marker alkaline phosphatase. Guanylate cyclase was partially soluble, partially particulate. In isopycnic gradients, particulate guanylate cyclase was present in other fractions than cAMP receptors and adenylate cyclase, but in similar ones to alkaline phosphatase. These observations are consistent with the hypothesis that cell-surface cAMP receptors and adenylate cyclase interact via a membrane-bound G-protein, whereas the receptors activate guanylate cyclase via a cytosolic factor. The adenylate cyclase activity in membranes obtained by sucrose gradient centrifugation was retained in the presence of various detergents, while with the same detergents the activity of particulate guanylate cyclase was lost. This adenylate cyclase was solubilized as assessed by gel filtration and centrifugation experiments, and it behaved heterogeneous in fractionation studies. In gel filtration, the major component eluted at a position corresponding to a Stokes radius of 4-7 nm. A purification of about 70-fold as compared to the cell homogenate was obtained by affinity chromatography of adenylate cyclase on ATP-Sepharose. We conclude that cell fractionation provides useful starting material for isolation and further study of Dictyostelium adenylate cyclase.
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PMID:Cell fractionation, detergent sensitivity and solubilization of Dictyostelium adenylate cyclase and guanylate cyclase. 288 13

The characteristics and localization of beta adrenoceptor subtypes in rat kidney sections have been examined using [125I]cyanopindolol and in vitro labeling combined with autoradiography. Binding was stereoselective since the (-)-isomers of propranolol and pindolol were some two orders of magnitude more effective as competitors than the (+)-isomers. Competition curves obtained using the subtype selective antagonists ICI 118,551 (beta-2) and betaxolol (beta-1) had low pseudo Hill coefficients and were resolved into two distinct components representing beta-1 (63%) and beta-2 adrenoceptors (37%). Combined autoradiographic and histochemical studies using nuclear emulsion-coated coverslips and alkaline phosphatase staining showed that the majority of receptors were in the renal cortex and in the outer band of the medulla with fewer receptors associated with the inner medulla, papilla and renal blood vessels. Delineation of beta-1 and beta-2 adrenoceptor subtypes with the selective antagonists betaxolol and ICI 118,551 indicated that the highly localized receptors were predominately of the beta-1 subtype, associated with glomeruli and with tubules that from their staining characteristics and topography represent distal and cortical collecting tubules with few if any receptors associated with proximal tubules. Beta-2 adrenoceptors were more diffusely distributed in the cortex and there were minor areas of localization in the inner medulla. Although some glomerular beta adrenoceptors probably play a role in control of renin release, their distribution throughout this structure indicates that they also control other functions. The distribution of beta adrenoceptors in tubules corresponds well with the known distribution of beta adrenoceptor-stimulated adenylate cyclase in rat kidney and indicates that these receptors subserve a physiological function.
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PMID:Localization of beta adrenoceptor subtypes in rat kidney by light microscopic autoradiography. 298 17

The human colon cancer line Caco-2 exhibits after confluency a concomitant increase of glycogen accumulation and an enterocytic differentiation. The purpose of this work was to investigate whether forskolin (FK), an activator of adenylate cyclase, would induce a permanent glycogenolysis and, if so, whether it would result in modifications of the differentiation pattern of the cells. FK activates adenylate cyclase in Caco-2 cells with an ED50 of 7 X 10(-6)M. Three different treatment protocols with FK (10(-5)M) were applied: 1) the cells were treated during all the time in culture (20 days); 2) the treatment was started after confluency; 3) the treatment was interrupted after confluency. The presence of FK results in a permanent stimulation of cAMP accumulation (10 to 20 fold the basal values) and in a permanently reduced glycogen content (30 or 50% of the control values). The rates of glucose consumption are increased three and five fold in protocols 1 and 3 respectively. These metabolic changes are associated with morphological changes (tightening of the intercellular spaces and shortening of the brush border microvilli) and with a dual inhibition of the activities of brush border hydrolases: a) an inhibition of the post-confluent increase of activity of sucrase, aminopeptidase N and alkaline phosphatase in the brush border enriched fraction; b) an inhibition of the post-confluent increase of activity of sucrase in the cell homogenate. A comparison of the results obtained in each protocol shows that the morphological modifications and the decrease of the enzyme activities in the brush border fraction are regularly associated with an increased cAMP accumulation, whereas the inhibition of the differentiation of sucrase is a direct consequence of the increase in glucose consumption and decrease in glycogen stores.
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PMID:Enterocytic differentiation and glucose utilization in the human colon tumor cell line Caco-2: modulation by forskolin. 298 31

This study documents the characteristics of a viral antigen-bearing cell line derived from co-culture of the bone from a 71-year-old woman with Paget's disease of bone and HEp-2 cells. The cell line has survived in continuous culture for 3 1/2 years and 185 subcultures. The cells are epithelioid in appearance, produce alkaline and acid phosphatase, increase alkaline phosphatase activity in response to 1,25-(OH)2-D3 and contain receptors for 1,25-(OH)2-D3. Immunofluorescent studies utilizing antisera to respiratory syncytial virus and measles virus reveal antigens of both viruses in the cells. These cells do not produce bone in culture and the adenylate cyclase activity found in their plasma membrane does not increase significantly in response to parathyroid hormone or calcitonin. The cells are not contact inhibited and form spherical colonies in agarose. They are aneuploid and have a modal number of 62-74 as well as HeLa markers. When injected into athymic mice, osteosarcomas are produced. These tumors continue to bear viral antigens. The availability of this cell line should aid in further studies of the viral antigens associated with Paget's disease of bone.
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PMID:A viral antigen-bearing cell line derived from culture of Paget's bone cells. 299 74

The role of cyclic adenosine 3',5'-monophosphate (cAMP) in inducing bone resorption was studied in neonatal mouse calvaria in vitro. Forskolin, a stimulator of adenylate cyclase, increased the medium calcium concentration at 96 hr of incubation, indicating enhanced bone resorption. Bone resorption was observed between 1 X 10(-4) and 1 X 10(-6) M forskolin; the maximal effect was at 1 X 10(-5) M and there was no effect at 1 X 10(-7) M. Lactic acid release was increased during the 96 hr of incubation in proportion to the calcium release in the media. The bone acid phosphatase activity was increased and the alkaline phosphatase activity was decreased. Bone carbonic anhydrase activity was increased more than twofold. Forskolin-induced bone resorption was significantly but incompletely inhibited by 10(-4) M acetazolamide, a carbonic acid anhydrase inhibitor. These findings support the concept that carbonic anhydrase plays a significant role in bone resorption.
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PMID:Forskolin-induced bone resorption in neonatal mouse calvaria in vitro. 300 59

The present study was undertaken to investigate the effect of the Hyp mutation and diet-induced hyperparathyroidism on renal responsiveness to PTH and forskolin and to determine whether the renal brush border membrane phosphate transport defect is expressed in the vitamin D- and calcium-deficient Hyp mouse. Our results indicate that PTH is a potent activator of cAMP synthesis in renal slices obtained from vitamin D-replete normal mice and Hyp littermates. However, in the mutants, the amount of cAMP produced in response to similar concentrations of PTH (0.005-5 U/ml) is 55% of normal (P = 0.0076). PTH-dependent cAMP synthesis is significantly reduced in both normal and Hyp mice fed the vitamin D-deficient low calcium diet, and under these conditions, genotype differences are no longer apparent. In contrast, forskolin-stimulated cAMP production is identical in vitamin D-replete normal and mutant mice. Furthermore, cAMP accumulation in response to forskolin is not decreased by diet-induced hyperparathyroidism in either genotype. Vitamin D and calcium deprivation results in a significant decrease in renal brush border membrane Na+-dependent phosphate transport in both genotypes, and under these conditions, the phosphate transport defect persists in Hyp mice. Finally, vitamin D and calcium deprivation has no effect on renal brush border membrane alkaline phosphatase activity. The present results suggest that the catalytic subunit of adenylate cyclase is intact in the mutant strain and that the blunted renal response to PTH in vitamin D-replete Hyp mice as well as in vitamin D- and calcium-deficient mice may be due to uncoupling of the PTH-receptor-adenylate cyclase system. The data also suggest that the expression of the renal phosphate transport defect in Hyp mice is independent of PTH status and alkaline phosphatase activity.
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PMID:Effect of the Hyp mutation and diet-induced hyperparathyroidism on renal parathyroid hormone- and forskolin-stimulated adenosine 3',5'-monophosphate production and brush border membrane phosphate transport. 300 90

Despite its acute inhibitory effect on bone formation in vitro, PTH has been shown to have an anabolic effect on bone in vivo and to stimulate cell proliferation in osteoblastic cell lines and organ cultures. We have examined the effects of PTH on cells derived from human trabecular bone and compared these effects with those on human skin fibroblasts. Human bone cells have the capacity to synthesize type I collagen and osteocalcin, and to respond to 1,25-dihydroxyvitamin D3 with an increase in the synthesis of osteocalcin and alkaline phosphatase. PTH stimulated adenylate cyclase activity at both low and high cell density. However, the same concentrations of hormone stimulated the proliferation of these cells only when they were cultured at a high cell density. The effect of PTH was bone cell specific in that no proliferative effect of PTH was detected in cultures of human skin fibroblasts obtained from the same donor and cultured under the same conditions. The effect of PTH on DNA synthesis by human bone cells may be important in the generation of a long term anabolic response to PTH.
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PMID:Parathyroid hormone stimulates the proliferation of cells derived from human bone. 300 59

Based on the finding that retinoic acid (RA) increases 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] receptor number in ROS 17/2 cells, we investigated the effects of RA on the ability of 1,25-(OH)2D3 to regulate alkaline phosphatase activity and PTH-responsive adenylate cyclase in these cells. A maximally effective dose of 1,25-(OH)2D3 (10(-8) M) caused a 75-80% increase in alkaline phosphatase activity and an approximately 70-75% attenuation of the cAMP response to PTH, while RA (10(-6) M) decreased alkaline phosphatase activity by 30-45% and decreased PTH-stimulated cAMP levels by approximately 20%. Preincubation with RA did not enhance the 1,25-(OH)2D3-induced increases in alkaline phosphatase activity. The ED50 values for control and RA-treated cultures were approximately 8 X 10(-10) M and 6 X 10(-10) M, respectively. With regard to PTH responsiveness, the effects of RA preincubation on the 1,25-(OH)2D3 attenuation of cAMP response varied with the concentration of 1,25-(OH)2D3. At low doses (less than 10(-9) M), the effects of 1,25-(OH)2D3 and RA were additive. At higher doses of 1,25-(OH)2D3, the effects of RA and 1,25-(OH)2D3 were not additive, and there were no differences between control- and RA-treated cultures. The ED50 values for control- and RA-treated cultures were 10(-10) M and 3 X 10(-11) M, respectively. None of the above effects were observed using equimolar doses of the vitamin D3 metabolites 24,25-dihydroxyvitamin D3 and 25-hydroxyvitamin D3. The data show that pretreating ROS 17/2A cells with RA to increase 1,25-(OH)2D3 receptors does not correspond with a concomitant increase in the cellular responsiveness to 1,25-(OH)2D3, as measured by increases in alkaline phosphatase activity and decreases in PTH-responsive adenylate cyclase.
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PMID:Modulation by retinoic acid of 1,25-dihydroxyvitamin D3 effects on alkaline phosphatase activity and parathyroid hormone responsiveness in an osteoblast-like osteosarcoma cell line. 301 60


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