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Impairment of hormone-stimulated cardiac adenylate cyclase activity in the genetically obese (fa/fa) Zucker rat

par Chatelain, Pierre ;Robberecht, Patrick ;De Neef, Philippe ;Camus, Jean Claude ;Poloczek, Piotr ;Christophe, Jean
Référence Pflügers Archiv, 390, 1, page (10-16)
Publication Publié, 1981

Article révisé par les pairs

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Résumé :

The age-related development of the capacity of the cardiac adenylate cyclase system to be stimulated with secretin, vasoactive intestinal peptide (VIP), glucagon, the beta-adrenergic agonist isoproterenol, Gpp(NH)p, and NaF was compared in obese (fa/fa) Zucker rats and their lean (FA/?) littermates. The obese (fa/fa) Zucker rats tested developed postweaning obesity associated with marked hypertriglyceridemia, mild hyperglycemia, and hyperinsulinism. At 4 weeks, there was already a 57% reduction in secretin-VIP-stimulated adenylate cyclase activity in fa/fa rats. At 12 weeks, the secretin-VIP-stimulation was reduced by 77%, and glucagon- and isoproterenol-stimulations by 16-21%. At 45 weeks, secretin-VIP-stimulation was reduced by 91%, glucagon- and isoproterenol stimulations by 34-42%, and Gpp(NH)p- and NaF-stimulations by 16-23%. The reductions of isoproterenol-, Gpp(NH)p-, and NaF-stimulations were totally or partially reversed in 30-week old fa/fa animals submitted for 5 weeks to severe food restriction that almost normalized the altered blood parameters. In sharp contrast, food restriction imposed a further decrease in secretin-VIP- and glucagon-stimulated adenylate cyclase activities. This pattern of impaired secretin-VIP-stimulated adenylate cyclase activity appeared limited to cardiac membranes in obese animals as the responses of liver, brain and anterior pituitary adenylate cyclase activities to secretin and/or VIP were unaltered. These results suggest that secretin-VIP receptors coupled to adenylate cyclase were rapidly and specifically altered in the heart of fa/fa Zucker rats.