G-proteins and beta-adrenergic stimulation of adenylate cyclase activity in the diabetic rat prostate.
BACKGROUND
The consequences of experimental diabetes on membrane lipids, beta-adrenergic stimulation of adenylate cyclase activity, and G-protein levels in the prostate gland are not defined.


METHODS
Prostatic membranes from control and streptozotocin (STZ)-diabetic rats were used to study adenylate cyclase stimulation as well as for immunodetection of stimulatory (alpha s) and inhibitory (alpha i) G-protein subunits. Changes in membrane lipid composition were estimated by [1-14C] acetate incorporation into lipid subclasses.


RESULTS
The efficacy of isoproterenol on stimulation of adenylate cyclase activity and the levels of alpha s, alpha i1/2, and alpha i3/0 G-protein subunits were drastically reduced in prostatic membranes from STZ-diabetic rats. Insulin treatment of diabetic rats tended to normalize G-protein levels, but it was ineffective on the poor adenylate cyclase response to isoproterenol or forskolin. However, it prevented enzyme desensitization to vasoactive intestinal peptide. The pattern of [1-14C] acetate incorporation into lipid subclasses did not vary with diabetes or insulin treatment.


CONCLUSIONS
STZ-induced diabetes results in desensitization for the beta-adrenergic response of adenylate cyclase, as supported by previous data on the low density of beta-adrenergic receptors and the present results on the general decrease of Gs and Gi proteins levels and even of the enzyme itself in the diabetic rat prostate.
Carmena
M J
MJ
Departamento de Bioquimica y Biología Molecular, Universidad de Alcalá, Spain.
Clemente
C
C
Carrero
I
I
Solano
R M
RM
Prieto
J C
JC
D000085:Acetates / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy / Q000201:enzymology*; D019204:GTP-Binding Proteins / Q000502:physiology*; D015151:Immunoblotting; D007328:Insulin / Q000627:therapeutic use; D007545:Isoproterenol / Q000494:pharmacology; D050356:Lipid Metabolism; D008297:Male; D011467:Prostate / Q000201:enzymology* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D000085:Acetates; D000318:Adrenergic beta-Agonists; D007328:Insulin; D005576:Colforsin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D007545:Isoproterenol