Fig. 5.

Response to isoproterenol. (A) Isolated papillary muscles from wt (n = 7) and TG (n = 9) mice were isolated and analyzed as described in the legend to Fig. 3 in the absence (CTL) and presence (Iso) of 100 nM isoproterenol applied to the surface of the muscles. (B) Hemodynamic measurements on whole hearts were taken after the administration of 2 μg/g isoproterenol through the jugular vein of anesthetized animals. Under resting conditions (CTL) and at the point of maximal changes as assessed by continuous hemodynamic recordings (Iso), ventricular tissue (n = 3 in each condition) was isolated, snap-frozen, and analyzed by immunoblotting with antibodies to PLN (1D11) and phosphorylated PLN (285). Numbers represent the mean ± SEM in arbitrary densitometric units. p, Pentameric PLN; m, monomeric PLN; m/p, the ratio of monomeric to pentameric PLN.