Inhibition of L-type but not T-type calcium channel current by a new dihydropyridine derivative, S11568.

S11568, (+-)((amino-2-ethoxy)-2-ethoxy]-methyl)-2-(dichloro-2', 3'-phenyl)-4-ethoxycarbonyl-3-methoxycarbonyl-5-methyl-6-dihydro-1,4-pyr idine HCl, is a new dihydropyridine derivative that is water soluble and relatively insensitive to light. The Ca2+ channel inhibitory activity of S11568 was tested in whole-cell patch clamp recordings from cultured embryonic chick cardiomyocytes in 40 mM Ba2(+)-containing medium that revealed T-type and L-type components of inward current through calcium channels. S11568 inhibited L-type Ca2+ current with an IC50 value near 1 microM but was without effect on the T-type barium current.