In voltage-clamped chromaffin cells PCA50941 (1 microM) and Bay K 8644 (1 microM) shifted the I-V relationship of whole-cell Ca2+ currents by about 5-10 mV towards more hyperpolarizing potentials.?At -20 mV, PCA50941 enhanced ICa by 195 +/- 16% and Bay K 8644 by 288 +/- 51%.?Stimulation of fura 2-loaded chromaffin cell suspensions with 17.7 K+/0.5 Ca2+ increased 3-fold the basal [Ca2+]i.?PCA50941 increased further the K(+)-evoked peak to 655 nM, and Bay K 8644 to 1129 nM.?In the presence of 5 mM Ca2+, PCA50941 or Bay K 8644 increased the [Ca2+] peaks to 427 and 350 nM, respectively[1].

PCA50941 potentiated the release of catecholamines from perfused bovine adrenal glands evoked by 30 s pulses of 17.7 mM K+ in a manner dependent on the [Ca2+]o.?Thus at 1, 2.5, 5 and 10 mM Ca2+, secretion was 2.3-, 3.8-, 5- and 4-fold greater than in control glands.?Bay K 8644 enhanced the K(+)-induced response 3- and 9-fold at [Ca2+]o of 0.25 or 0.5 mM, respectively;?at higher [Ca2+]o the potentiation was similar to that of PCA50941[1].