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 effect of parathyroid hormone and calcitonin on the renal excretion of phosphate, calcium, and cyclic AMP was evaluated in the thyroparathyroidectomized hamster, a mammal apparently reisstant to the phosphaturic effect of parathyroid hormone. Parathyroid hormone did not increase phosphate excretion, although it decreased excretion of calcium and increased urinary excretion of cyclic AMP. This lack of a phosphaturic response to parathyroid hormone was not reversed by administration of 25-OH vitamin D or infusions of calcium or phosphate. Calcitonin, another potentially phosphaturic hormone, also vailed to increase phosphate excretion but markedly elevated urinary excretion of cyclic AMP. In hamsters pretreated with infusion of urinary ammonium chloride, which decreased plasma and urinary pH, both parathyroid hormone and calcitonin increased excretion of phosphate as well as that of cyclic AMP. Acetazolamide had no phosphaturic effect in ammonium chloride-loaded hamsters, and it decreased cyclic AMP and calcium excretion. Alkalinization of urine by acetazolamide did not prevent the phosphaturic effect of parathyroid hormone in ammonium chloride-loaded hamsters, but it blocked the increase in urinary cyclic AMP excretion. Parathyroid hormone and calcitonin both stimulated adenylate cyclase in a cell-free system (600-g pellet) from hamster renal cortex, elevated tissue cyclic AMP levels, and activated protein kinase in tissue slices from hamster renal cortex. In acid medium, the increase in cyclic AMP and activation of protein kinase in response to parathyroid hormone was diminished, but addition of acetazolamide restored responsiveness of both parameters to control values. Acetazolamide, on the other hand, did not influence adenylate cyclase or its response to parathyroid hormone or cyclic AMP phosphodiesterase activity. We conclude that the lack of a phosphaturic effect of parathyroid hormone and calcitonin in the hamster depends on steps in the cellular action of these hormones, steps that are sensitive to pH subsequent to cyclic AMP generation and protein kinase activation. In addition, acetazolamide may potentiate the phosphaturic effect of parathyroid hormone by promoting accumulation of cyclic AMP in tissue. Thus, the hamster is a particularly useful model for studies of syndromes in which there is renal resistance to phosphaturic hormones.
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PMID:Mechanism of resistance to the phosphaturic effect of the parathyroid hormone in the hamster. 1 74

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

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

Many hormones initiate their biologic actions by augmenting the intracellular concentrations of 3',5'-adenosine monophosphate (cyclic AMP). The nucleotide has been found in body fluids; its determination in plasma and urine can be performed by a rapid, simple and specific method: the cyclic AMP assay kit of the Radiochemical Centre (Amersham, England). The assay is based on the competition between unlabelled cAMP and a fixed quantity of the tritium labelled compound for binding to a bovine muscle protein which has a high specificity and affinity for cAMP. Different factors must be considered in evaluating the 24 h urinary content of the nucleotide: the renal or extrarenal origin of cAMP and the functional status of the kidneys. In basal conditions the urinary cAMP excretion is significantly correlated with creatinine excretion (n = 67; r = 0.47; p less than 0.001) thus confirming that the most part of cAMP excreted is derived from the plasma by glomerular filtration. Parathyroid hormone (PTH) stimulates adenylate cyclase predominantly in the renal cortex, whereas vasopressin (ADH) stimulated the enzyme in the medulla; thus PTH and ADH could increase the amount of cAMP in the urine from the renal source. In a case of diabetes insipidus and infusion of ADH caused a prompt rise in cAMP urinary excretion. In 5 normals an infusion of bovine synthetic parathyroid hormone caused an increased excretion of cAMP that preceded the phosphaturic response. An infusion of salmon synthetic calcitonin caused a rise in phosphate excretion and no increase in cAMP urinary content. As it concerns the two calciotopic hormones, PTH and CT, it is reasonable to assume that renal receptors are distinct. The 24 h urinary excretion of cAMP in 55 control subjects (3613 +/- 1460 D.S. n moles) was contrasted with the lower excretion in 25 elderly subjects (70-93 years: 1804 +/- 699 n moles), with the high cAMP excretion in a patient with hyperparathyroidism (that fell to normal values following removal of the parathyroid adenoma) and with the low cAMP excretion in patients with primary or surgical hypoparathyroidism. The mean 24 h cAMP excretion in patients with renal insufficiency was significantly decreased when compared to control subjects. These findings and recent reports confirm that the 24 h urinary output of cAMP may be considered an useful index of pharathyroid function in man.
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PMID:[The diagnostic value of the determination of cyclic 3',5'-adenosine monophosphate (cAMP) in urine]. 19 Jun 33

The regulation of vitamin D metabolism by the kidney is now known to be multifactorial. Three regulatory factors are discussed: 1,25(OH)2D3 itself; parathyroid hormone, and phospate. The influence of 1,25(OH)2D3 probably depends on new protein synthesis, while the mode of action of phosphate is unknown. Parathyroid hormone is not essential for regulation but may have an important biological role. The direction of its effect varies, perhaps due to a complex interrelation of changes in calcium and phosphorus metabolism and the level of kidney adenyl cyclase activity.
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PMID:Regulation of vitamin D: an evolutionary view. 21 35

The two first steps of the renal cellular action of parathyroid hormone and of calcitonin are the hormonal binding onto specific receptors and the stimulation of adenylate cyclase by the hormone-receptor complex producing an increase in the intra-cellular concentration of 3'-5' cyclic adenosine monophosphate (cyclic AMP). Specific glomerular and tubular receptors for parathyroid hormone have been demonstrated using either tritiated parathyroid hormone or an indirect technique with 125 I labelled specific antibodies. Tubular receptors are localized both in the proximal and distal segments of the nephron. Parathyroid hormone stimulates glomerular and tubular adenylate cyclase. The main unsolved problem is the difficulty for demonstrating high affinity binding sites and stimulation of adenylate cyclase at low physiological concentrations of parathyroid hormone. In man, administration of parathyroid hormone produces a marked increase in the urinary excretion of cyclic AMP chiefly concerning its nephrogenous fraction. The peak of excretion is early and precedes the decrease in phosphate tubular reabsorption. Tubular receptors for calcitonin have been demonstrated using 125 I labelled salmon calcitonin. Calcitonin stimulates renal adenylate cyclase in only some segments of the nephron allowing receptors for calcitonin to be localized in the wide ascending branch of Henle's loop and the initial part of the convoluted distal tubule. In the presence of guanylnucleotides, binding of calcitonin onto its receptors and activation of adenylate cyclase are observed in the range of physiological concentrations of calcitonin in the rat. In man, administration of calcitonin produces a moderate increase in the urinary excretion of cyclic AMP coming from a non renal tissue.
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PMID:[Renal receptors of parathyroid hormone and calcitonin (author's transl)]. 21 63

Parathyroid hormone (PTH) and glucagon increase the urinary fractional excretion of phosphate, but insulin administration is associated with a decreased fractional excretion of phosphate. It was the purpose of this study to determine whether insulin will antagonize the effects of PTH and glucagon on cAMP levels and protein kinase activation of rat renal cortex. In situ incubation studies were performed on rat renal cortical slices exposed to insulin, PTH, and glucagon. Insulin alone did not affect the tissue cAMP and cGMP levels or the state of protein kinase activation. Preincubation of slices with insulin, however, did significantly inhibit increases in protein kinase activation induced by both PTH and glucagon. Insulin also significantly inhibited PTH-stimulated increases in tissue cAMP levels, but did not blunt the elevations of cAMP levels induced by glucagon. Insulin (10(-9) M) had no effect on either the in vitro activity of adenylate cyclase, basal or PTH-stimulated, or on the activities of low Km cytosolic or membrane-bound cAMP phosphodiesterase. The data show that insulin antagonizes activation of protein kinase by both PTH and glucagon in renal cortex. Separate mechanisms are probably involved for PTH and glucagon interaction. The antiphosphaturic effect of insulin in vivo may result in part from this antagonism at the cellular level.
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PMID:Insulin inhibition of hormone-stimulated protein kinase systems of rat renal cortex. 22 Aug 84

Prolactin was shown to activate adenylate cyclase in broken cellular enzyme preparations from rat renal medulla. Likewise, vasopresin was effective on this enzyme system. Parathyroid hormone was similarly active in the renal cortex. The simultaneous administration of vasopressin and prolactin to medullary kidney slices did not result in an additive effect in stimulating medullary adenyl cyclase. Audioradiographic techniques revealed a selective and prolonged localization of intravenously injected 125I-prolactin to the thick limb of the loop of Henle, the distal tubule and the collecting duct. It is concluded that prolactin activates medullary adenylate cyclase, and may do so by occupying ADH receptors.
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PMID:Prolactin-induced stimulation of rat renal adenylate cyclase and autoradiographic localization to the distal nephron. 86 55

Fresh frozen bovine parathyroid glands were defatted in acetone, when extracted with phenol. Following trichloroacetic acid precipitation, the resultant peptides were chromatographed on Sephadex G-100. Parathyroid hormone (BPTH) characteristically elutes in the fourth peak. However, we also observed significant hormonal activity, both biological and immunological, in the fifth elution peak. The peak V material had potent hypercalcemic activity in the rat and chick, and stimulated adenylate cyclase activity in the rat renal cortex bioassay. This material was further purified by ion exchange chromatography on carboxymethylcellulose in 8 M urea. The biological activity of the purified peptide (3700 MRC units/mg) was equivalent to that of the native hormone on a molar basis. Amino acid analysis, carboxypeptidase digestion, and partial Edman sequence analysis identified this material as BPTH 1-65, a hormonal fragment lacking the C-terminal 19 residues of the 84 residue hormone molecule. Several immunoassays using different anti-PTH antisera had variable reactivity toward the BPTH 1-65 fragment, showing that it may be useful for further characterizing antibody recognition sites. The presence of a lysine residue at position 65 suggests a tryptic-like cleavage may be responsible for the genesis of this hormonal fragment. Further investigation will be necessary to determine if this peptide has physiological significance.
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PMID:A biologically active hormonal fragment isolated from bovine parathyroid glands (BPTH 1-65). 114 77

1. Incubation of parathyroid hormone with plasma membranes from rat kidney cortex resulted in rapid loss of all hormal activity. 2. Chick kidney membranes showed no ability to inactivate parathyroid hormone even with prolonged incubation. 3. Biologically active, labelled parathyroid hormone was degraded to fragments by rat kidney membranes, but not by chick kidney. 4. Hormone-responsive adenylate cyclase activity in a mixture of rat and chick kidney membranes was additive. 5. Parathyroid hormone bound specifically to chick kidney palsma membranes. 6. It is concluded that hormone in activation during incubation has little relevance to the effectiveness of parathyroid hormone in stimulating adenylate cyclase activity in kidney, and furthermore that failure of chick kidney to metabolize the hormone is not the explanation for the greater sensitivity of this species to the hormone.
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PMID:Hormone metabolism and response of adenylate cyclase to parathyroid hormone in kidney. 123 5


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