Effects of a novel antihypertensive drug, cilnidipine, on catecholamine secretion from differentiated PC12 cells.
Effects of a novel dihydropyridine type of antihypertensive drug, cilnidipine, on the regulation of the catecholamine secretion closely linked to the intracellular Ca2+ were examined using nerve growth factor (NGF)-differentiated rat pheochromocytoma PC12 cells. By measuring catecholamine secretion with high-performance liquid chromatography coupled with an electrochemical detector, we showed that high K+ stimulation evoked dopamine release from PC12 cells both before and after NGF treatments. Cilnidipine depressed dopamine release both from NGF-treated and untreated PC12 cells in a concentration-dependent manner. In contrast, inhibition by nifedipine was markedly decreased in the differentiated PC12 cells. With intracellular Ca2+ concentration ([Ca2+]i) measurements using fura 2, the elevation of high K+-evoked [Ca2+]i was separated into nifedipine-sensitive and -resistant components. The nifedipine-resistant [Ca2+]i increase was also blocked by cilnidipine, as well as omega-conotoxin-GVIA. By the use of the conventional whole-cell patch-clamp technique, the compositions of the high-voltage-activated Ca2+ channel currents in the NGF-treated PC12 cells were divided into types: L-type, N-type, and residual current components. It was also estimated that cilnidipine at 1 and 3 micromol/L strongly blocked the N-type current without affecting the residual current. These results suggest that cilnidipine inhibits catecholamine secretion from differentiated PC12 cells by blocking Ca2+ influx through the N-type Ca2+ channel, in addition to its well-known action on the L-type Ca2+ channel.
Uneyama
H
H
Life Science Laboratories, Central Research Laboratories, Ajinomoto Co, Inc, Yokohama, Totsuka, Japan. LL_UNEYAMA@te3.ajinomoto co.jp
Uchida
H
H
Yoshimoto
R
R
Ueno
S
S
Inoue
K
K
Akaike
N
N
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism*; D004095:Dihydropyridines / Q000494:pharmacology*; D016716:PC12 Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats
D000959:Antihypertensive Agents; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D002395:Catecholamines; D004095:Dihydropyridines; C065927:cilnidipine; D002118:Calcium