Stimulatory Protein in Cardiomyopathic BIO 53.58 Syrian Hamsters

Background The effects of chronic exercise training on myocardial contractility and ,B-adrenergic signal transduction in hearts with left ventricular dysfunction have not been determined. Methods and Results Fourteen-week-old cardiomyopathic BIO 53.58 and normal F1B Syrian hamsters underwent 10 weeks of treadmill training and were compared with 24-weekold BIO 53.58 and F1B untrained controls. Left ventricular isovolumic maximum positive dP/dt and peak developed pressure were significantly lower in BIO 53.58 than in F1B controls. Exercise training improved left ventricular contractile indices in BIO 53.58 but not F1B hamsters. The left ventricular ,B-adrenergic receptor number (Bi,n0) was similar in BIO 53.58 and F1B controls. Basal adenylate cyclase activity (ACA) and ACAs stimulated by isoproterenol, 5'-guanylylimidodiphosphate (GppNHp), sodium fluoride, and forskolin were significantly lower in BIO 53.58 than in F1B controls. The functional activity of stimulatory guanine nucleotide-binding protein (G), as determined by reconstitution with S49 lym-