Effect of metabolic acidosis on the PTH receptor-adenylate cyclase system of canine kidney

1985 ◽  
Vol 249 (4) ◽  
pp. F566-F572
Author(s):  
E. Bellorin-Font ◽  
J. Humpierres ◽  
J. R. Weisinger ◽  
C. L. Milanes ◽  
V. Sylva ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Metabolic Acidosis ◽  
Adenylate Cyclase ◽  
Receptor Binding ◽  
Binding Capacity ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Serum Bicarbonate ◽  
Blood Ph

The phosphaturic action of parathyroid hormone (PTH) is blunted during metabolic acidosis. Previous studies suggest that the activation of renal cortical adenylate cyclase by PTH is decreased under this condition. However, the mechanisms underlying the defect are not completely defined. The present studies were designed to examine the interaction of PTH with its receptor-adenylate cyclase system in basolateral cortical membranes from dogs with metabolic acidosis. Chronic metabolic acidosis was induced in seven normal dogs. Venous blood pH decreased to 7.21 +/- 0.01 and serum bicarbonate to 12.58 +/- 0.32 meq/liter. In seven control dogs blood pH was 7.38 +/- 0.002 and serum bicarbonate was 20.14 +/- 0.26 meq/liter. The kidneys were surgically removed and basolateral membranes were prepared by differential centrifugation and ultracentrifugation in discontinuous sucrose density gradients for studies of adenylate cyclase activity and hormone-receptor binding. Metabolic acidosis resulted in a significant decrease in PTH-dependent adenylate cyclase activity (Vmax 2,119 +/- 150 pmol cAMP X mg prot-1 .30 min-1 vs. 3,548 +/- 116 in the controls). The PTH concentration giving half-maximal activation of adenylate cyclase was unchanged. However, PTH-receptor binding showed similar affinity and binding capacity in both groups of membranes. Basal enzyme activity was also similar. In the presence of the GTP analogue 5'-guanylylimidodiphosphate, PTH-dependent adenylate cyclase activity remained markedly decreased in the acidotic dog membranes compared with the controls. The ability of NaF to stimulate enzyme activity was also depressed in the membrane of acidotic dogs. Enzyme activity in the presence of Mn2+ was similar in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of benzyl alcohol on PTH receptor-adenylate cyclase system of canine kidney

1985 ◽  
Vol 248 (1) ◽  
pp. E31-E35
Author(s):  
K. J. Martin ◽  
C. L. McConkey ◽  
T. J. Stokes
Keyword(s):  
Enzyme Activity ◽  
Adenylate Cyclase ◽  
Benzyl Alcohol ◽  
Membrane Fluidity ◽  
Phospholipid Composition ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Hormone Sensitive ◽  
Canine Kidney

In many systems, perturbations of membrane architecture by changes of lipid and phospholipid composition have been shown to alter the activity of membrane-bound enzymes. The present studies examined the effect of benzyl alcohol, an agent that has been shown to increase membrane fluidity, on the parathyroid hormone (PTH)-sensitive adenylate cyclase system of canine kidney. Benzyl alcohol progressively increased basal adenylate cyclase activity up to fourfold and maximal enzyme activity in the presence of PTH, GTP, guanylimidodiphosphate, and sodium fluoride by four- to sixfold. In the presence of 20 mM Mn2+ (no Mg2+), conditions under which enzyme activity is devoid of influence of guanine nucleotides or hormones, benzyl alcohol was without effect. PTH binding was increased by 25% in the presence of benzyl alcohol without a change in binding affinity. Fluorescent polarization studies using diphenylhexatriene showed a decrease in fluorescence anisotropy in the presence of benzyl alcohol. The results suggest that benzyl alcohol facilitates the interaction of the components of the adenylate cyclase system, presumably by increasing membrane fluidity. Alterations of membrane fluidity may be a potent means of regulating hormone sensitive adenylate cyclase activity.

Regulation of PTH receptor-adenylate cyclase system of canine kidney: influence of Mn2+ on effects of Ca2+, PTH, and GTP

1982 ◽  
Vol 242 (5) ◽  
pp. F457-F462
Author(s):  
E. Bellorin-Font ◽  
J. Tamayo ◽  
K. J. Martin
Keyword(s):  
Enzyme Activity ◽  
Adenylate Cyclase ◽  
Metal Ions ◽  
Guanine Nucleotides ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Guanine Nucleotide ◽  
Hormone Binding ◽  
Stimulation Of

Metal ions play important roles in the regulation of the activation of adenylate cyclase. Previous studies have suggested that an important site of action of metal ions is at or closely related to the nucleotide regulatory protein. The present studies examine the nature of the regulation of enzyme activity by divalent cations and the influence of Mn2+ on hormone binding and stimulation of adenylate cyclase. Studies were performed in canine renal cortical membranes. Substitution of Mg2+ by Mn2+ was associated with a progressive decline in the ability of GTP or PTH to stimulate adenylate cyclase activity. Mn2+ did not alter specific binding of an iodinated PTH analogue. However, in spite of the loss of guanine nucleotide stimulation of enzyme activity, the effects of guanine nucleotide on PTH binding were not altered in the presence of Mn2+. Substitution of Mg2+ by Mn2+ abolished the inhibitory effect of Ca2+ on basal adenylate cyclase activity. Similarly, the effects of GTP or PTH to enhance the inhibitory effects of Ca2+ on enzyme activity were abolished in the presence of Mn2+. Since Mg2+ and Ca2+ compete for a common allosteric site and Mn2+ abolished the effects of these cations, it would appear that Mn2+ also competes for the binding site of Mg2+ and Ca2+. The present studies demonstrating that Mn2+ does not affect hormone binding or the actions of guanine nucleotides on hormone binding yet totally eliminates the effect of GTP on enzyme activity indicate that the effect of Mn2+ occurs at the level of the interactions of the nucleotide regulatory component with the catalytic unit. In addition, these data suggest that there are two functionally distinct sites of guanine nucleotides with different ionic requirements.

THYROTROPHIN-RESPONSIVE ADENYLATE CYCLASE ACTIVITY IN THYROID TOXIC ADENOMA

1979 ◽  
Vol 92 (4) ◽  
pp. 658-668 ◽  
Author(s):  
Roberto S. Toccafondi ◽  
Carlo M. Rotella ◽  
Annalisa Tanini ◽  
Patrizia Fani ◽  
Paolo Arcangeli
Keyword(s):  
Enzyme Activity ◽  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Thyroid Tissue ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Toxic Adenoma ◽  
Normal Thyroid Tissue ◽  
Normal Thyroid

ABSTRACT The adenylate cyclase system was studied in hyperfunctioning autonomous nodules in comparison with normal thyroid tissue. The basal, TSH- and NaF-stimulated adenylate cyclase activities were tested in purified plasma membrane preparations. Basal enzyme activity in membranes from hyperfunctioning nodules was variable and the response to TSH was either normal, low or absent. The present study demonstrates that an intact adenylate cyclase activity, hyporesponsive to TSH, may exist in the cell membrane of the adenoma.

Sensitization of frog erythrocyte adenylate cyclase system by tumor-promoting phorbol diesters

1985 ◽  
Vol 63 (8) ◽  
pp. 983-986 ◽  
Author(s):  
Ponnal Nambi ◽  
David R. Sibley ◽  
Robert J. Lefkowitz
Keyword(s):  
Enzyme Activity ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Adenylate Cyclase ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Erythrocyte Membranes ◽  
Adenylate Cyclase System ◽  
Kinase C ◽  
Cell Supernatant

Preincubation of frog erythrocyte lysates with tumor-promoting phorbol diesters leads to an increase in adenylate cyclase activity. This stimulatory effect of phorbol diesters was specific. Incubation with 12-O-tctradecanoylphorbol 13-acetate led to increases in basal (38%) and isoproterenol- (40%), fluoride- (25%), and Mn-stimulated (68%) adenylate cyclase activities compared with control. The inactive phorbol diesters (4α-phorbol 12,13-didecanoate and β-phorbol) were ineffective in promoting increases in adenylate cyclase activity. The effect of active phorbol diesters was also observed on isolated frog erythrocyte membranes in the absence of cell supernatant, although to a much lesser extent than in the whole lysates. Addition of the cell supernatant or of purified protein kinase C to the membranes maximized the sensitization by the phorbol diesters. These data are consistent with the notion that some component(s) of the adenylate cyclase system is (are) phosphorylated by protein kinase C, resulting in an enhancement of enzyme activity.

scholarly journals Differential effects of non-ionic detergents on microsomal and sarcolemmal adenylate cyclase in cardiac muscle

1978 ◽  
Vol 175 (1) ◽  
pp. 171-180 ◽  
Author(s):  
Prakash V. Sulakhe ◽  
Njanoor Narayanan
Keyword(s):  
Enzyme Activity ◽  
Sarcoplasmic Reticulum ◽  
Adenylate Cyclase ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Protein Ratio ◽  
Guinea Pig Heart ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Ionic Detergent ◽  
Triton X

1. About 4 and 23% of the homogenate adenylate cyclase activity was recovered in the microsomal and sarcolemmal fractions isolated from guinea-pig heart ventricles. 2. Cardiac microsomal adenylate cyclase activity [basal as well as p[NH]ppG (guanyl-5′-yl imidodiphosphate)- and NaF-stimulated] was increased over 2-fold in the presence of Lubrol-PX (0.01–0.1%). 3. The sarcolemmal enzyme, however, showed concentration-dependent inhibition caused by the detergent under all assay conditions, except when p[NH]ppG was included in the assay. In the latter case, the detergent (0.01–0.02%) caused a modest increase (30–45%) in enzyme activity. 4. Another non-ionic detergent, Triton X-100, also stimulated the microsomal cyclase and inhibited the sarcolemmal enzyme. 5. With either membrane fraction, Lubrol-PX solubilized the enzyme when the detergent/membrane protein ratio was 2.5 (μmol of detergent/mg of protein). 6. The findings with homogenate and a washed particulate fraction resembled those obtained with sarcolemma, and those with isolated sarcoplasmic reticulum resembled those with microsomal preparations. 7. p[NH]ppG, and to some extent NaF, protected the detergent-induced inactivation of the enzyme observed at higher detergent concentrations (0.5% Lubrol-PX and 0.05–0.5% Triton X-100). 8. In the absence of detergents, p[NH]ppG increased the basal enzyme activity about 2-fold in microsomal fractions, but did not appreciably stimulate the sarcolemmal enzyme. Isoproterenol, on the other hand, increased the sarcolemmal enzyme activity (>2-fold) in the presence of p[NH]ppG and caused only moderate stimulation (31%) of the microsomal enzyme under these conditions. 9. These findings support the view that, although the bulk of adenylate cyclase resides in heart sarcolemma (plasma membrane), the microsomal activity cannot be accounted for solely by contamination of the microsomal fraction with sarcolemma, as has been suggested by others [Besch, Jones & Watanabe (1976) Circ. Res.39, 586–595; Engelhard, Plut & Storm (1976) Biochim. Biophys. Acta451, 48–61]. Further, the results of this study show that cardiac sarcoplasmic-reticulum membranes possess this enzyme.

Temporal effects of cytokines on neonatal cardiac myocyte Ca2+ transients and adenylate cyclase activity

1997 ◽  
Vol 272 (4) ◽  
pp. H1937-H1944 ◽  
Author(s):  
R. J. Bick ◽  
J. P. Liao ◽  
T. W. King ◽  
A. LeMaistre ◽  
J. B. McMillin ◽  
...  
Keyword(s):  
Adenylate Cyclase ◽  
Cardiac Myocyte ◽  
Prolonged Exposure ◽  
Neonatal Rat ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Short Exposure ◽  
Adenylate Cyclase System ◽  
Long Term Treatment

This study investigates the hypothesis that inflammatory cytokines, interleukin (IL)-1alpha IL-1beta, and tumor necrosis factor (TNF), influence cardiac function by affecting calcium homeostasis and that this effect is mediated by the beta-adrenergic-adenylate cyclase system. After 4 days in culture, neonatal rat ventricular myocytes were treated with cytokines (10 ng/ml) for short (2 h) or longer (18 h) times. Myocyte calcium, contractility, and adenylate cyclase were measured under each condition. Anticipated stepwise increases in adenylate cyclase and intracellular calcium were found in controls (non-cytokine-treated) with 10(-7) M isoproterenol, 10(-7) M isoproterenol + 0.1 mM guanosine triphosphate, and 10(-9) M forskolin. Cells in the presence of cytokine for 2 h show increased basal calcium levels but no changes in adenylate cyclase activities, and isoproterenol fails to elevate adenylate cyclase levels or affect contractile shortening. After long-term treatment with IL-1beta or TNF, but not IL-1alpha, the significantly elevated levels of basal systolic calcium remain, and isoproterenol increases adenylate cyclase activity, unlike after short exposure. Forskolin maximally activates adenylate cyclase following both short- and long-term incubation, but the stepwise increase in activity is blunted following prolonged exposure. Thus short-term cytokine treatment blocks the adrenergic receptor-mediated increases in adenosine 3',5'-cyclic monophosphate, dissociating adenylate cyclase activation from cytokine-mediated increases in cell calcium, whereas longer treatment apparently produces direct affects on adenylate cyclase. Time-dependent differences in contractile response were found with IL-1alpha at 2 h and TNF at 18 h, implying that myofibrillar responsiveness to increased cytoplasmic calcium is dependent on both cytokine species and exposure time.

scholarly journals Catecholamine-sensitive adenylate cyclase of caudate nucleus and cerebral cortex. Effects of guanine nucleotides

1977 ◽  
Vol 164 (1) ◽  
pp. 67-74 ◽  
Author(s):  
P V Sulakhe ◽  
N L Leung ◽  
A T Arbus ◽  
S J Sulakhe ◽  
S H Jan ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Cerebral Cortex ◽  
Adenylate Cyclase ◽  
Caudate Nucleus ◽  
Protein S ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Biphasic Effect ◽  
Site Binding ◽  
Stimulation Of

1. GTP and GMP-P(NH)P (guanyl-5'-yl imidodiphosphate) were observed to increase the stimulation of neural adenylate cyclase by dopamine (3,4-dihydroxyphenethylamine) and noradrenaline. 2. GMP-P(NH)P had a biphasic effect on the enzyme activity. 3. Preincubation of membranes with GMP-P(NH)P activated the enzyme by a process dependent on time and temperature. Catecholamines increased the speed and the extent of this activation. 4. Membrane fractions contained high- and low-affinity sites for GMP-P(NH)P binding: this binding was due to protein(s) of the membrane preparations. 5. Low-affinity-site binding of GMP-P(NH)P appeared to be related to the stimulatory effect on the adenylate cyclase activity.

Relationship of follicle stimulating hormone (FSH)-sensitive adenylate cyclase activity to FSH binding in immature rat ovaries following administration of pregnant mare serum gonadotrophin

1982 ◽  
Vol 101 (4) ◽  
pp. 625-629 ◽  
Author(s):  
C. Y. Lee ◽  
L. E. Reichert
Keyword(s):  
Adenylate Cyclase ◽  
Dose Response ◽  
Follicle Stimulating Hormone ◽  
Optimal Dose ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Immature Rat ◽  
Pregnant Mare Serum Gonadotrophin ◽  
Stimulating Hormone

Abstract. The time and dose-response relationships of human follicle stimulating hormone (hFSH)-sensitive adenylate cyclase activity to hFSH binding was studied in the immature rat ovary following an sc injection of pregnant mare serum gonadotrophin (PMSG). When an optimal dose of PMSG (10 IU/rat) was administered, a marked increase in hFSH-sensitive activity was observed at day 2, followed by a sharp decline at day 3. This was accompanied by a parallel rise and fall in ovarian hFSH binding activity. When immature rats were given various doses (5–100 IU/rat) of PMSG for 2 days, hFSH-sensitive adenylate cyclase activity increased sharply and maximal stimulation was obtained at 10 IU/rat. A close correlation was also observed with respect to dose-response for hCG-sensitive adenylate cyclase and hCG binding activities. It is concluded that: 1) PMSG administration with an optimal dose to the immature rat induced ovarian FSH and LH-hCG receptors, and an adenylate cyclase system highly sensitive to hFSH and hCG, and 2) the acquisition and responsiveness of adenylate cylcase to gonadotrophins are closely related to the appearance and the numbers of gonadotrophin receptors.

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