The Effects Of PTH On Calcium Mobilization, Currents Of Ca～(2+) Channels And α_1G MRNA Expressing Of T-type Ca～(2+)Channels In Cardiomyocytes Of Rat With CRF

Part I Effects of PTH on Calcium Mobilization and Apoptosis in Rat Cardiomyocytes and Interference of CalcitriolObjective To study the effects of parathyroid hormone (PTH) oncalcium mobilizations |hypertrophy and apoptosis in i]at cardiomyocytes and their mechanism, and the protective effects of calcitriol.Methods Hypertrophic response in cardiomyocyte of neonatal rat was assayed by measuring cell surface area and protein content. The fluorescent intensity (FI) of intracellular calcium concentration ( [Ca2+]i ) was measured by confocal microscope using Fluo-3/AM as fluorescent indicator. Apoptosis was determined by flow cytometer and electron microscope.Results PTH1-34at the concentration of 0, 0.01, 0.1 and 1 μ mol.L-1elevated FI of [Ca2+]i in cardiomyocytes from 48.78 ?6.70> 47.78 ?6.14,45.58 + 6.11 51.10 + 9.33 to 48.82 ?.31, 54.63 + 3.60, 63.82?.21(P< 0.01) and 78.66+ 10.04 ( P < 0.01) respectively, when [Ca2+]i ofextracelluar fluid was 2.5mmol.L-1. However, when extracelluar fluidcontained zero calcium, or cardiomyocytes was pre-treated by nifedipine 10μ mol.L-1, PTH1-34 ( 1 μ mol.L" ) did not increase FI significantly. The beatrate of rat cardiomyocytes changed similarly as FI of [Ca2+]i.After 7d exposure to PTH1-34 of 0.01 and 0.1 u mol.L-1 , [Ca2+]i, surface area and protein content,and apoptosis rate(APO) of cardiomyocytes were 186.0 ?3.6, 287.3+33.7 jam2, 291.4 ?21.2 pg/cell, 6.97 ?1.00% and 217.9 + 22.2, 368.4 +51.2 μ m2, 346.0 ?33.6 pg/cell, 12.58 ?1.75% respectively, which were significantly higher than control group ( 77.7 ?19.9, 218.7+19.9 μm2, 223.0 + 13.7 pg/cell and 0.12 + 0.11%, P<0.01 ) , especially those in high concentration group. If the cells were co-treated by nifedipine and PTH1-34, the markers above were improve significantly, but they were still higher markedly than normal. When the cells were co-treatedby 0.001 $ mol/L calcitriol and 0.1 u mol/L PTH1-34 the markers above were 114.3 ?29.9, 245.2 ?20.0 $ m2, 243.2 ?12.99pg/cell and 3.43 ?0.40% , which were improved significantly. However, when the concentration of calcitriol was 0.1 $. mol/L, the results were 207.8 ?33.6, 364.7 ?8.3 urn2 , 351.6 ?17.4pg/cell and 12.19 ?1.03%, which did not change markedly.Conclusions (1)PTH1-34 dose-dependently increased the beat rate and[Ca2+ ]i in rat cardiomyocytes. (2) Hypertrophy and apoptosis in cardiomyocytes were induced by 7d exposure to PTH1-34, and were inhibited by proper concentration of calcitriol, but were not by high concentration of calcitriol. (3)The evidences induced by 1-34 above were, at least partly, attributed to augmented entry of calcium into cells via voltage-dependent Ca2+ channels.