Strassheim D, Palmer T, Milligan G, Houslay MD. Alterations in G-protein expression and the hormonal regulation of adenylate cyclase in the adipocytes of obese (fa/fa) Zucker rats.
Biochem J 1991;
276 ( Pt 1):197-202. [PMID:
1903933 PMCID:
PMC1151164 DOI:
10.1042/bj2760197]
[Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Attenuated maximal activations by forskolin, Mn+. NaF or guanosine 5'-[gamma-thio]triphosphate (GTP[S]) were noted for adenylate cyclase activity in adipocytes from obese (fa/fa) Zucker rats compared with their lean (Fa/Fa) littermates. GTP[S] achieved half-maximal activation of adenylate cyclase at some 10-fold lower concentrations in membranes from lean animals compared with those from obese. Levels of the 42 and 45 kDa forms of Gs were some 40-50% lower in membranes from obese animals, and levels of Gi-1 and Gi-3 were some 62-65% lower. No differences in levels of Gi-2 alpha-subunits or G-protein beta-subunits were observed. Gi function, as assessed by inhibiting forskolin-stimulated adenylate cyclase, achieved by prostaglandin E1, nicotinate and phenylisopropyladenosine, was similar in membranes from both lean and obese animals. Levels of beta-adrenoceptors were some 50% lower in membranes from obese animals. It is suggested that the attenuated activation of adenylate cyclase by stimulatory ligands in membranes from obese animals may be caused by decreases in both Gs and receptors, and that this may contribute to the attenuated lipolytic response seen in adipocytes from such animals.
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