EFFECTS OF M-NISOLDIPINE ON AORTIC CALCIUM ACCUMULATION IN RATS WITH VASCULAR CALCIUM OVERLOAD

AIM: To study the effects of a novel calcium, channel blocker, m-nisol dipine, on vascular calcium overload (VCO) at both tissue and cellular levels. METHODS: VCO was induced in Wister rats by treatment with col ecalciferol (Col, 400 000 IU . kg(-1), po) and an aqueous mixture of e thanol and polyethyleneglycol-400 for 3 b. The tissue and subcellular calcium contents of aorta were determined by atomic absorption spectro meter 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 th e dose-response relationship of m-Nis displayed a bell shape, with inh ibition ratio of 24 % only for m-Nis 2.5 mg . kg(-1). The effect of ve rapamil (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 rati os of 72 % for cytoplasm and 76 % for mitochondrion. The calcium accum ulation in nucleus was reduced to a lesser degree than those in cytopl asm and mitochondrion. CONCLUSION: As for aorta in VCO rats, m-Nis mai nly had conspicuous inhibition on intracellular VCO in medial smooth m uscle cells, particularly in cytoplasm and mitochondrion, but with lit tle effect on extracellular calcium deposition at tissue level.