Effects of Calcium Antagonists on the PC12 Cell Damage Induced by Hypoxia

ABSTRACT

Hypoxia-induced cell damage is known to be mediated by increase in intracellular calcium. In the present study, the effect of calcium channel blockers on the hypoxia-induced cell damage was investigated in iat pheochromocytoma cells line, PC12 cells. The cultured cells were exposed to hypoxia under 95% N2 plus 5% C02 gas phase and incubated in the media devoid of fetal bovine seruril The cell demage was assessed by measuring the release of lactate dehydrogenase (LDH) from the cells into the incubation media. Exposure of the cells to hypoxia for 2 hours caused a 28% of the total LDH to be released from cells -into media. The pretreatment of the cells with 1 mM each of diltiazem, nifedipine, and verapamil depressed the LDH release to the extent of 52%, 42%, and 30% inhibition, respectively. The inhibitory effects of diltiazem and verapamil were more marked at 1 mM than at 10 mM. The influx of 45 Ca2+ into the cells was rapidly increased within 2 minutes after exposure of the cells to hypoxia. Diltiazem at 1 mM almost completely inhibited Ca2+ influx, while nifedipine and verapamil exhibited only, 30% inhibition of Ca2- influx. The results lend support to the notion that mcreased intracellular calcium triggers a series of cascade reactions leadmg to cell death. It is suggested that the inhibitory effects of various calcium antagonists on hypoxia-induced cell damage differ from each other in their potency.