INCREASED 1,4-DIHYDROPYRIDINE BINDING-SITES IN SERUM-STIMULATED CARDIOMYOCYTE HYPERTROPHY

Altered calcium channel number or function may be associated with myoc ardial hypertrophy. Treatment of cultured neonatal rat cardiomyocytes with norepinephrine or serum results in cellular hypertrophy without a n increase in cell number. Cell culture is a convenient system for exa mining possible changes in channels and receptors associated with hype rtrophy. The specific objective of this study was to measure the densi ty of calcium channels in serum-free (as control), norepinephrine and serum-treated cardiomyocyte cultures. Measurements of high affinity [H -3]nitrendipine binding and (45) Ca++ uptake were made in K+-depolariz ed cardiomyocyte cultures. We report that there is an increased densit y of functional voltage-sensitive calcium channels in the serum-stimul ated model of cardiomyocyte hypertrophy. This increased density of cal cium channels in the serum-treated cells may represent a mechanism res ponsible for initiating and promoting cardiomyocyte hypertrophy.