[Biochemical effects of ryodipine (foridon)--a new calcium antagonist and derivative of 1,4-dihydopyridine].

Ryodipine (foridon)--2, 6-dimethyl-3,5-dicarbomethoxy-4-(o-difluoromethoxyphenyl)-1, 4-dihydropyridine--similarly to nifedipine but at a lesser degree than nicardipine causes an increase of cAMP concentration in the slices of the rabbit myocardium and aorta. This property of 1,4-dihydropyridines is reflected in their effect on the uptake of 45Ca2+ by the myocardial strips. In the range of concentrations of 10(-4)-10(-6)M inhibition of 45Ca2+ transport is enhanced with a decrease of concentrations of the drugs. Under inactivation of potential-dependent transport of Ca2+, 1,4-dihydropyridines enhance the uptake of 45Ca2+. The similar effect was found at incubation of the myocardial slices in a polarizing buffer (2.68 mM K+). Verapamil, irrespective of the degree of depolarization (60,123 mM K+), suppressed in a linear dependence the uptake of 45Ca2+ and failed to influence this process in the absence of potential-dependent transport of Ca2+. By its biochemical effects ryodipine does not differ from the known derivatives of 1,4-dihydropyridine but has, like nifedipine and nicardipine, significant differences as compared with verapamil.