Trapidil and other 5-triazolo-(1, 5-alpha)-pyrimidine derivatives as calcium channel blockers in 108CC5 cells.

The action of trapidil (RocornalR) and its derivatives AR 12-456 and AR 12-160 on the inward calcium current (ICa) was studied in mouse neuroblastoma x rat glioma hybrid cells of the line 108CC5 under voltage clamp conditions by means of a suction pipette method. A dissociation constant of the calcium channel-trapidil complex of 277 microM was estimated for the initial inhibition of ICa by trapidil. Half maximal block of ICa was produced by 80 +/- 20 microM AR 12-456 and 500 +/- 150 microM AR 12-160.