Developmental changes of protein kinase C and Gs alpha in hypertrophic cardiomyopathic hamster hearts.

Protein kinase C (PKC) and GTP-binding proteins (G-proteins) are known to be major determinants in the modulation of cardiac function. In this study, we examined the developmental changes of PKC and the alpha-subunit of the stimulatory guanosine triphosphate binding protein (Gs alpha) in hypertrophic cardiomyopathic Syrian hamster (BIO 14.6) hearts, before the onset of hypertrophy (30 days old) and at the peak of hypertrophy (6 months old) and compared these with age-matched control hamster (BIO RB) hearts. At 30 days, cardiac PKC activity was similar between BIO 14.6 and BIO RB both in the membrane (117.1 +/- 9.9 pmol/min/mg vs 131.2 +/- 12.7 pmol/min/mg in controls, n = 8) and in the cytosolic fractions (213.1 +/- 22.0 pmol/min/mg vs 186.6 +/- 23.9 pmol/min/mg in controls, n = 9). At 6 months, PKC activity was significantly higher in BIO 14.6 than in controls, both in the cardiac membrane (131.9 +/- 7.1 pmol/min/mg vs 40.7 +/- 4.7 pmol/min/mg in controls, n = 8, p < 0.00001) and cytosol (77.9 +/- 2.1 pmol/min/mg vs 54.6 +/- 3.3 pmol/min/mg in controls, n = 6, p < 0.0005). In BIO RB hearts, membrane and cytosolic PKC activities were significantly reduced at 6 months compared with those at 30 days of age (p < 0.001). However, the membrane PKC activity in 6-month-old BIO 14.6 was maintained at the level of the 30-day-old hearts. On the other hand, the relative immunoreactive amounts of Gs alpha were similar between BIO RB and BIO 14.6 hearts at 30 days and at 6 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)