A STUDY OF GLAUCINE-INDUCED RELAXATION OF RAT AORTA

The vasorelaxant effect of glaucine, the major alkaloid of Platycapnos spicata (L.) Bernh., was studied. At concentrations of 10 muM - 0.3 m M in normal Krebs solution it was almost equieffective in relaxing K+- induced and noradrenaline-induced tension in rat aortic rings without endothelium, with IC50 values of 160 +/- 16 muM and 90 +/- 14 muM resp ectively. In experiments in a calcium-free medium, 10 muM glaucine str ongly inhibited noradrenaline-induced contractions. Glaucine (0.3 mM) did not affect basal uptake of Ca-45, but induced uptake was reduced t o 100% (K+) and 97.7 % (noradrenaline) of the basal value. These resul ts suggest that glaucine has an intracellular effect and also acts on the cell membrane by blocking voltage-dependent and receptor-operated calcium channels.