Increased 1,4-dihydropyridine binding sites in serum-stimulated cardiomyocyte hypertrophy.

ABSTRACT

Altered calcium channel number or function may be associated with myocardial hypertrophy. Treatment of cultured neonatal rat cardiomyocytes with norepinephrine or serum results in cellular hypertrophy without an increase in cell number. Cell culture is a convenient system for examining possible changes in channels and receptors associated with hypertrophy. The specific objective of this study was to measure the density of calcium channels in serum-free (as control), norepinephrine and serum-treated cardiomyocyte cultures. Measurements of high affinity [3H]nitrendipine binding and 45Ca++ uptake were made in K(+)-depolarized cardiomyocyte cultures. We report that there is an increased density of functional voltage-sensitive calcium channels in the serum-stimulated model of cardiomyocyte hypertrophy. This increased density of calcium channels in the serum-treated cells may represent a mechanism responsible for initiating and promoting cardiomyocyte hypertrophy.