The work has been done on primary heart culture from neonatal rat ventricle. Cardiomyocyte
hypertrophy was modelled using
noradrenaline (NA),
angiotensin II (AII) and fetal serum, respectively. Cell
hypertrophy of primary heart cultures was assessed by measuring the surface area, the scope of
protein synthesis estimated by 3H-leucine autoradiography and the contents of
nucleic acids in
gallocyanin-
chromalum stained cardiomyocytes. The structure of myofibrillar apparatus was studied by
rhodamine-conjugated
phalloidin and indirect immunofluorescence of muscle
alpha-actinin. Treatment with 10(-6) M NA increased 3H-leucine incorporation in 9-day old heart culture by 42% without changing cell size. AII in a dose 1 microM stimulated
protein synthesis activity by 1.3 fold and the surface area by 1.7 fold, both in 2- and 9-day old primary heart cultures. The maximum stimulation of cell
hypertrophy was provided by the medium supplemented with fetal serum.
RNA contents in the cytoplasm of cardiomyocytes increased by 7.8 fold and the myocardial cell size by 2.9 fold in serum-supplemented culture by 9 days of cultivation. In the medium with fetal serum, amounts of cardiomyocytes with
tetraploid nuclei reached 33%, against 14% in control. Coculturing of myocardiocytes and fibroblasts rendered effects of fetal serum on the growth of myocardiocytes. Cultivation in the presence of 1 microM
enalapril, an
ACE inhibitor, suppressed the development of cardiac muscle cells
hypertrophy. The effect of
enalapril depended on the degree of cellular
hypertrophy. Addition of 10 microM
amiloride to the medium lowered the
protein synthesis by 29% independently on the initial cellular
hypertrophy.