Effect of the genetic background and specific mutation on adenylate cyclase activity in obesity syndromes.
Adenylate cyclase activity and its modulation by guanine nucleotides and isoproterenol were assessed in adipocyte membranes of mice with mutations causing different genetic obesity syndromes. The object was to determine whether the defect in inhibitory modulation observed in the obese (ob/ob) mouse was also present in the diabetes (db/db) mouse. The data show that adipocyte adenylate cyclase in both the ob/ob and the db/db mouse is resistant to activation by isoproterenol. The response to guanosine triphosphate (GTP) differed between the two mutants, such that an inhibitory phase was visible in the db/db but not in the ob/ob membranes. Moreover, pertussis toxin attenuated the inhibitory effect of GTP and significantly stimulated cyclase activity in the db/db but not in the ob/ob membranes. The data show that the two mutations affect the expression of adenylate cyclase activity via different mechanisms.
Bégin-Heick
N
N
Department of Biochemistry, University of Ottawa, Canada.
Coleman
D L
DL
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology / Q000235:genetics; D004789:Enzyme Activation / Q000187:drug effects; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009154:Mutation; D009765:Obesity / Q000201:enzymology / Q000235:genetics*
D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D000262:Adenylyl Cyclases; D007545:Isoproterenol