Desensitization of the ?-adrenoceptor-adenylate cyclase system of immature erythrocytes by in-vivo treatment of rats with isoprenaline

1981 ◽  
Vol 317 (4) ◽  
pp. 294-301 ◽  
Author(s):  
G. Wiemer ◽  
G. Kaiser ◽  
J. Dietz ◽  
M. Reinhardt ◽  
A. Wellstein ◽  
...  
Keyword(s):  
Adenylate Cyclase ◽  
Adenylate Cyclase System ◽  
In Vivo Treatment

Changes in skeletal muscle glycogenolysis after prolonged cold exposure and repeated injections with isoproterenol

1979 ◽  
Vol 57 (9) ◽  
pp. 938-943 ◽  
Author(s):  
M. C. Thibault ◽  
C. Côté ◽  
J. Vallières
Keyword(s):  
Adenylate Cyclase ◽  
Cold Stress ◽  
Tibialis Anterior ◽  
Skeletal Muscles ◽  
Glycogen Phosphorylase ◽  
Phosphorylase Kinase ◽  
Adenylate Cyclase System ◽  
Great Capacity ◽  
Contracting Muscle

Wistar rats were either given daily injections of isoproterenol (ISO) (15 μg/100 g per day) or exposed to 6 °C for 4 or 12 weeks (cold acclimated (CA)). After a 4-week exposure to cold and to ISO, acute cold stress (4 h at –18 °C) produced a 48% depletion of glycogen in the tibialis anterior of control rats while it did not significantly affect the levels in ISO-treated and CA animals. ISO treatment enhanced the in vivo response of phosphorylase kinase and glycogen phosphorylase to epinephrine (EPI) in the tibialis anterior, a fast contracting muscle. In the soleus, a slow contracting muscle known to be more sensitive to catecholamines, chronic treatment with ISO also resulted in increased basal and EPI-stimulated adenylate cyclase activity. No evidence could be found for an alteration of the glycogenolytic pathway (adenylate cyclase system, phosphorylase kinase, and glycogen phosphorylase) in fast contracting skeletal muscles of CA rats. It is concluded that ISO-treated and CA rats, which have a great capacity for nonshivering thermogenesis, do not rely on their muscle carbohydrate reserves during cold stress. It might be suggested that plasma levels of catecholamines higher than those produced by exposure to 6 °C are required to alter glycogenolytic mechanisms in fast contracting rat skeletal muscles.

Control of adipose tissue lipolysis in ectotherm vertebrates

1992 ◽  
Vol 263 (4) ◽  
pp. R857-R862 ◽  
Author(s):  
R. H. Migliorini ◽  
J. S. Lima-Verde ◽  
C. R. Machado ◽  
G. M. Cardona ◽  
M. A. Garofalo ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Adenylate Cyclase ◽  
Lipolytic Activity ◽  
Adenylate Cyclase System ◽  
Triacylglycerol Lipase ◽  
Membrane Bound ◽  
Adipose Tissue Lipolysis ◽  
Toad Bufo

Lipolytic activity of fish (Hoplias malabaricus), toad (Bufo paracnemis), and snake (Philodryas patagoniensis) adipose tissue was investigated in vivo and in vitro. Catecholamines or glucagon did not affect the release of free fatty acids (FFA) by incubated fish and toad adipose tissue. Catecholamines also failed to activate snake adipose tissue lipolysis, which even decreased in the presence of epinephrine. However, glucagon stimulated both the lipolytic activity of reptilian tissue in vitro and the mobilization of FFA to plasma when administered to snakes in vivo. The release of FFA from incubated fish, amphibian, and reptilian adipose tissue increased markedly in the presence of cAMP or xanthine derivatives, inhibitors of phosphodiesterase. Forskolin or fluoride, activators of specific components of the adenylate cyclase system, strongly stimulated toad adipose tissue lipolysis. The data suggest that adipocyte triacylglycerol lipase of ectotherm vertebrates is activated by a cAMP-mediated phosphorylation and that the organization of the membrane-bound adenylate cyclase system is similar to that of mammals.

scholarly journals Stabilization and solubilization of bovine corpus-luteum adenylate cyclase. The effects of guanosine triphosphate, guanosine 5′-[β,γ-imido]triphosphate, sodium fluoride and Tris/hydrochloric acid concentration on enzyme activity

1978 ◽  
Vol 169 (1) ◽  
pp. 133-142 ◽  
Author(s):  
John L. Young ◽  
David A. Stansfield
Keyword(s):  
Adenylate Cyclase ◽  
Corpus Luteum ◽  
Active State ◽  
Adenylate Cyclase System ◽  
Hydrochloric Acid Concentration ◽  
Bovine Corpus Luteum ◽  
Ionic Detergent ◽  
Stimulation Of

1. Adenylate cyclase of the washed 600g sediment of bovine corpus-luteum homogenate is stimulated by p[NH]ppG (guanosine 5′-[β,γ-imido]triphosphate), the imido analogue of GTP, and to a lesser extent by GTP itself. Activation by p[NH]ppG is not reversed by extensive washing before assay, but can, however, be reversed by NaF. 2. Both p[NH]ppG and NaF stabilize the enzyme during incubation at 37°C. NaF also causes an irreversible activation, but only of part of the potentially NaF-activatable adenylate cyclase; there are possibly two components of the adenylate cyclase system, which can be distinguished by their response to NaF. 3. Solubilization of the adenylate cyclase activity in the 600g sediment, by using the non-ionic detergent Lubrol-PX, gave variable yields. A relationship between the magnitude of NaF stimulation of the 600g-sediment enzyme and the yield of soluble activity derived from the sediment was recognized. The results suggest that the pre-existing state of the enzyme complex in vivo is reflected by the response in vitro to NaF and may determine the success with which activity can be solubilized. 4. The absolute yields of soluble activity could be increased by p[NH]ppG preactivation of the 600g sediment. During the development of the maximally active state by preincubation with p[NH]ppG the enzyme passes through a stage in which Lubrol solubilization is increased, but the maximally active state is itself less amenable to solubilization. p[NH]ppG activation causes the appearance of NaF-inhibited states, which appear to be preferentially solubilized by Lubrol-PX.

Epinephrine Induces von Willebrand Factor Release from Cultured Endothelial Cells: Involvement of Cyclic AMP-dependent Signalling in Exocytosis

1997 ◽  
Vol 77 (06) ◽  
pp. 1182-1188 ◽  
Author(s):  
Ulrich M Vischer ◽  
Claes B Wollheinn
Keyword(s):  
Endothelial Cells ◽  
Adenylate Cyclase ◽  
Von Willebrand Factor ◽  
Umbilical Vein ◽  
Free Calcium ◽  
Camp Content ◽  
Von Willebrand ◽  
Willebrand Factor

Summaryvon Willebrand factor (vWf) is released from endothelial cell storage granules after stimulation with thrombin, histamine and several other agents that induce an increase in cytosolic free calcium ([Ca2+]i). In vivo, epinephrine and the vasopressin analog DDAVP increase vWf plasma levels, although they are thought not to induce vWf release from endothelial cells in vitro. Since these agents act via a cAMP-dependent pathway in responsive cells, we examined the role of cAMP in vWf secretion from cultured human umbilical vein endothelial cells. vWf release increased by 50% in response to forskolin, which activates adenylate cyclase. The response to forskolin was much stronger when cAMP degradation was blocked with IBMX, an inhibitor of phosphodiesterases (+200%), whereas IBMX alone had no effect. vWf release could also be induced by the cAMP analogs dibutyryl-cAMP (+40%) and 8-bromo-cAMP (+25%); although their effect was weak, they clearly potentiated the response to thrombin. Epinephrine (together with IBMX) caused a small, dose-dependent increase in vWf release, maximal at 10-6 M (+50%), and also potentiated the response to thrombin. This effect is mediated by adenylate cyclase-coupled β-adrenergic receptors, since it is inhibited by propranolol and mimicked by isoproterenol. In contrast to thrombin, neither forskolin nor epinephrine caused an increase in [Ca2+]j as measured by fura-2 fluorescence. In addition, the effects of forskolin and thrombin were additive, suggesting that they act through distinct signaling pathways. We found a close correlation between cellular cAMP content and vWf release after stimulation with epinephrine and forskolin. These results demonstrate that cAMP-dependent signaling events are involved in the control of exocytosis from endothelial cells (an effect not mediated by an increase in [Ca2+]i) and provide an explanation for epinephrine-induced vWf release.

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