AIM: To study the effects of a novel calcium channel blocker, m-nisoldipine, on vascular calcium overload (VCO) at both tissue
and cellular levels. METHODS: VCO was induced in Wistar rats by treatment with colecalciferol (Col, 400 000 ID· kg-1, po) and an aqueous mixture of ethanol and polyethyleneglycol-400 for 3 d. The tissue and subcellular calcium contents of aorta were
determined by atomic absorption spectrometer and
electron probe microanalysis, respectively. RESULTS: Chronic treatment with
m-nisoldipine (m-Nis, 1 - 15 mg·kg-1, po, bid) only had mild inhibition on the elevation of total calcium in aorta, and the dose-response relationship of m-Nis displayed a bell shape, with inhibition ratio of 24 % only for m-Nis 2.5 mg · kg-1. The effect of verapamil (12.5 mg·kg-1, po, bid) was a little better than that of m-Nis. The intracellular VCO in medial smooth muscle cells of aorta were remarkably inhibited by m-Nis (2.5 mg·kg-1). with inhibition ratios of 72 % for cytoplasm and 76 % for mitochondrion. The calcium accumulation in nucleus was reduced to a lesser degree than those in cytoplasm and mitochondrion. CONCLUSION: As for aorta in VCO rats, m-Nis mainly had conspicuous inhibition on intracellular VCO in medial smooth muscle cells, particularly in cytoplasm and mitochondrion, but with little effect on extracellular calcium deposition at tissue level.