scholarly journals Stimulation of glucose transport in rat adipocytes by insulin, adenosine, nicotinic acid and hydrogen peroxide. Role of adenosine 3′:5′-cyclic monophosphate

1979 ◽  
Vol 178 (2) ◽  
pp. 381-389 ◽  
Author(s):  
Wayne M. Taylor ◽  
Mitchell L. Halperin
Keyword(s):  
Cyclic Amp ◽  
Nicotinic Acid ◽  
Glucose Transport ◽  
Pentose Phosphate ◽  
High Cell ◽  
Stimulatory Action ◽  
Rat Adipocytes ◽  
Cell Concentrations ◽  
Stimulation Of

Glucose transport into adipocytes of the rat was measured by monitoring the conversion of [1-14C]glucose into 14CO2. Glucose transport was made rate-limiting by increasing the flux through the pentose phosphate pathway with phenazine methosulphate, an agent that rapidly reoxidizes NADPH. Under these conditions, the observed rate of glucose disappearance from the incubation medium was about 20% higher than the rate of conversion of the C-1 of glucose into 14CO2. Apparent rates of glucose transport were significantly increased by insulin, H2O2, adenosine and nicotinic acid. Stimulation of the apparent rate of glucose transport by insulin was dependent on adipocyte concentration, the hormone being most effective at relatively high cell concentrations. Adenosine and nicotinic acid further enhanced the maximum stimulation of glucose transport by insulin. Potentiation of insulin action by adenosine was more pronounced at lower cell concentrations. At relatively high cell concentrations the stimulatory action of insulin was markedly decreased by adenosine deaminase. Stimulation of apparent rates of glucose transport by the compounds noted above were antagonized by agents that increased intracellular cyclic AMP concentrations (theophylline and isoprenaline) and by dibutyryl cyclic AMP. Intracellular concentrations of cyclic AMP were significantly lowered when adipocytes were incubated with insulin, H2O2, adenosine or nicotinic acid. These effects were observed under basal conditions or when intracellular cyclic AMP concentrations were elevated by theophylline or isoprenaline. On the basis of the above data, we suggest that insulin, H2O2, adenosine and nicotinic acid may all stimulate glucose transport in rat adipocytes by lowering the intracellular cyclic AMP concentration. These data therefore support the hypothesis that cyclic AMP inhibits glucose transport in rat adipocytes.

Stimulation of glucose transport in rat adipocytes by calcium

1979 ◽  
Vol 57 (6) ◽  
pp. 692-699 ◽  
Author(s):  
Wayne M. Taylor ◽  
Lena Hau ◽  
Mitchell L. Halperin
Keyword(s):  
Glucose Transport ◽  
Maximum Velocity ◽  
Pentose Phosphate ◽  
Calcium Flux ◽  
Intracellular Camp ◽  
Rat Adipocytes ◽  
Phosphorylation Mechanism ◽  
Rate Limiting ◽  
Camp Levels ◽  
Stimulation Of

Glucose transport in rat adipocytes was studied by monitoring the conversion of [1-14C]-glucose to 14CO2 in a system where glucose transport was made rate-limiting by increasing the flux through the pentose phosphate pathway with phenazine methosulphate, an agent which rapidly reoxidizes NADPH. Calcium increased both basal and insulin-stimulated apparent rates of glucose transport by approximately 40%. The maximum velocity of the apparent rate of glucose transport was increased by extracellular calcium both in the presence or absence of insulin. There was no change in the glucose concentration required for half-maximal rates of 14CO2 production. Calcium also enhanced the stimulation of apparent rates of glucose transport by insulin when examined over a range of hormone concentrations. Adipocyte cAMP concentrations were significantly lowered by calcium under conditions which led to increased apparent rates of glucose transport. In contrast, cobalt and nickel, antagonists of calcium action, elevated adipocyte cAMP levels and inhibited apparent rates of glucose transport. Agents which inhibit transmembrane calcium flux (verapamil, tetracaine, and procaine) inhibited apparent rates of glucose transport despite a reduction in adipocyte cAMP concentration.On the basis of the above data we suggest that calcium may increase apparent rates of glucose transport in rat adipocytes both by lowering intracellular cAMP concentration and by a further mechanism independent of changes in the level of cAMP. These results are consistent with the hypothesis that glucose transport in rat adipocytes may be controlled, in part, by a cAMP-induced phosphorylation mechanism.

scholarly journals The role of insulin in the modulation of glucagon-dependent control of phenylalanine hydroxylation in isolated liver cells

1987 ◽  
Vol 242 (3) ◽  
pp. 655-660 ◽  
Author(s):  
M J Fisher ◽  
A J Dickson ◽  
C I Pogson
Keyword(s):  
Cyclic Amp ◽  
Insulin Action ◽  
Phenylalanine Hydroxylase ◽  
Liver Cells ◽  
Phosphorylation State ◽  
Isolated Liver Cells ◽  
The Impact ◽  
Isolated Liver ◽  
Stimulation Of

The stimulation of phenylalanine hydroxylation in isolated liver cells by sub-maximally effective concentrations of glucagon (less than 0.1 microM) is antagonized by insulin (0.1 nM-0.1 microM). This phenomenon is a consequence of a decrease in the glucagon-stimulated phosphorylation of phenylalanine hydroxylase from liver cells incubated in the presence of insulin. The impact of insulin on the phosphorylation state and activity of the hydroxylase is mimicked by incubation of liver cells in the presence of orthovanadate (10 microM). A series of cyclic AMP and cyclic GMP analogues enhanced phenylalanine hydroxylation: in each case insulin diminished the stimulation of flux. These results are discussed in the light of the characteristics of insulin action on other metabolic processes.

Possible role of cyclic GMP in stimulus-secretion coupling by salt gland of the duck

1979 ◽  
Vol 237 (5) ◽  
pp. C200-C204 ◽  
Author(s):  
D. J. Stewart ◽  
J. Sax ◽  
R. Funk ◽  
A. K. Sen
Keyword(s):  
Cyclic Amp ◽  
Guanylate Cyclase ◽  
Cyclic Gmp ◽  
Salt Gland ◽  
Domestic Ducks ◽  
Stimulus Secretion Coupling ◽  
Stimulation Of

Stimulation of salt galnd secretion in domestic ducks in vivo increased the cyclic GMP concentration of the tissue, but had no effect on cyclic AMP levels. Methacholine, which is known to stimulate sodium transport by the glands both in vivo and in vitro, stimulated ouabain-sensitive respiration in salt gland slices. Cyclic GMP stimulated ouabain-sensitive respiration to the same extent as methacholine. Guanylate cyclase stimulators, hydroxylamine and sodium azide, also stimulated ouabain-sensitive respiration. The stimulation of ouabain-sensitive respiration by methacholine was blocked either by atropine or by removal of calcium from the incubation medium. The stimulation of ouabain-sensitive respiration by cyclic GMP still occurred in the absence of calcium. The above observations seem to indicate that cyclic GMP acts as a tertiary link in the process of stimulus-secretion coupling in the tissue.

Stimulation of aldosterone biosynthesis by sodium sequestration: role of angiotensin II

1982 ◽  
Vol 243 (6) ◽  
pp. E450-E457
Author(s):  
J. Muller ◽  
E. G. Lund ◽  
L. Hofstetter ◽  
D. B. Brunner ◽  
P. Haldy
Keyword(s):  
Angiotensin Ii ◽  
Enzyme Inhibitor ◽  
Zona Glomerulosa ◽  
High Dose ◽  
Converting Enzyme ◽  
Bilateral Nephrectomy ◽  
Stimulatory Action ◽  
Sodium Sequestration ◽  
Stimulation Of

The role of angiotensin II in the stimulation of aldosterone biosynthesis by sodium sequestration in potassium-deficient rats was assessed by experiments involving 1-day angiotensin II infusion, converting enzyme inhibition, and bilateral nephrectomy. In intact rats, only an extremely high dose of exogenous angiotensin II imitated the stimulatory effects of polyethylene glycol-induced edema on the conversions of deoxycorticosterone and corticosterone to 18-hydroxycorticosterone and aldosterone. Treatment with the converting enzyme inhibitor captopril as well as bilateral nephrectomy blocked the aldosterone-stimulating action of edema. This inhibition was prevented by the simultaneous infusion of angiotensin II in captopril-treated rats but not in nephrectomized animals. According to these results, angiotensin II is an essential mediator in the stimulation of aldosterone biosynthesis by sodium sequestration. However, the role of the kidneys appears to be twofold. First, they act through the secretion of renin. In addition, a second yet unknown kidney factor is necessary for a full response of the zona glomerulosa to the stimulatory action of angiotensin II.

scholarly journals Stimulation of glucose transport in Clone 9 cells by insulin and thyroid hormone: role of GLUT-1 activation

1996 ◽  
Vol 1314 (1-2) ◽  
pp. 140-146 ◽  
Author(s):  
Mangala Shetty ◽  
Ashok K Kuruvilla ◽  
Faramarz Ismail-Beigi ◽  
John N Loeb
Keyword(s):  
Thyroid Hormone ◽  
Glucose Transport ◽  
Glut 1 ◽  
Stimulation Of

Effect of lanthanum on the inotropic response of isoproterenol: role of the superficially bound calcium

1985 ◽  
Vol 63 (9) ◽  
pp. 1106-1112 ◽  
Author(s):  
Ahmad B. Fawzi ◽  
John H. McNeill
Keyword(s):  
Cyclic Amp ◽  
Positive Inotropic Effect ◽  
Direct Action ◽  
Maximum Response ◽  
Inotropic Response ◽  
Guinea Pig Heart ◽  
Low Concentrations ◽  
Stimulation Of ◽  
Calcium Pool

Mammalian myocardial contractility is believed to be related to the amount of calcium contained in a highly labile superficial calcium pool. The purpose of this study was to determine the role of such sites in the positive inotropic effect of isoproterenol. Lanthanum, an ion that is restricted to the extracellular space and that displaces the superficially bound calcium, was selected as a tool for this investigation. In Langendorff preparations of the guinea pig heart, lanthanum decreased the basal contractility index (+ dP/dtmax) in a concentration-dependent fashion (0.05–3μM) and blocked the inotropic response of isoproterenol in a noncompetitive manner (0.25–3 μM). Three-micromolar lanthanum (i) reduced basal contractility and the maximum response to isoproterenol by 97 and 95%, respectively, (ii) had no significant effect (p > 0.05) on basal and isoproterenol-induced cyclic AMP levels, and (iii) had no effect on the Kd of [3H]nitrendipine binding, but reduced the Bmax by 31%. While 1 μM lanthanum reduced basal contractility and the maximum response to isoproterenol by 90 and 70%, respectively, it had no effect on [3H]nitrendipine binding. These results suggest that the effects of such low concentrations of lanthanum (≤3 μM) are not related to a direct action on the calcium channels and are not mediated by an inhibition of isoproterenol stimulation of the enzyme adenylate cyclase. Therefore, one interpretation of these results suggests that superficially bound calcium is required for the inotropic response of isoproterenol.

Stimulation of steroid secretion by adrenocorticotropin injections and by arginine vasopressin infusions: no evidence for a direct stimulation of the human adrenal by arginine vasopressin

1991 ◽  
Vol 125 (4) ◽  
pp. 348-353 ◽  
Author(s):  
V. Bähr ◽  
J. Hensen ◽  
O. Hader ◽  
T. Bölke ◽  
W. Oelkers
Keyword(s):  
Arginine Vasopressin ◽  
Plasma Aldosterone ◽  
Regression Coefficients ◽  
Minor Importance ◽  
Cortisol Secretion ◽  
Plasma Acth ◽  
Direct Stimulation ◽  
Stimulatory Action ◽  
Stimulation Of

Abstract. Arginine vasopressin stimulates the secretion of adrenocorticotropin. A direct stimulatory effect of AVP on cortisol as well as aldosteron secretion has been postulated by several investigators. To study the possible role of a direct stimulatory action of AVP on the adrenal cortex, normal volunteers were treated with incremental injections of ACTH or with incremental infusions of AVP which raised plasma AVP levels to a maximum of 256±16 pmol/l. In both situations, a significant (p<0.001) linear correlation between plasma ACTH and plasma cortisol was observed. The regression coefficients were not different (p>0.5). Plasma aldosterone was stimulated by both treatments, but the weakly positive correlation between plasma ACTH and plasma aldosterone was not significant for either stimulus. Thus, in man, a direct stimulatory effect of AVP on cortisol secretion cannot be demonstrated. A direct effect of AVP on aldosterone cannot be definitely excluded, but is certainly of minor importance.

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