Noradrenaline, vasopressin and angiotensin increase Ca2+ influx by opening a common pool of Ca2+ channels in isolated rat liver cells.
Noradrenaline, vasopressin and angiotensin increase Ca2+ influx by opening a common pool of Ca2+ channels in isolated rat liver cells.
复制标题
去甲肾上腺素、加压素和血管紧张素通过在离体大鼠肝细胞中打开共同的 Ca2+ 通道池来增加 Ca2+ 的流入。
作者：
J. Mauger;J. Poggioli;F. Guesdon;M. Claret
通过测量45Ca2+摄取的初始速率，在离体大鼠肝细胞中研究了Ca2+动员激素去甲肾上腺素、血管加压素和血管紧张素对Ca2+单向内流的影响。三种激素均增加Ca2+内流，去甲肾上腺素、血管加压素和血管紧张素的EC50值（产生半最大效应的浓度）分别为0.15微米、0.44 nM和0.8 nM。去甲肾上腺素和血管紧张素的作用在加入细胞后的几秒钟内就很明显，而由加压素引起的Ca2+内流的增加则稍微延迟（5-15秒）。只要受体被激素占据，Ca2+内流的激活就会保持。在不同的外部Ca2+浓度下，静息和激素刺激的Ca2+流量的测量显示michaelis - menten型动力学与饱和通道模型兼容。去甲肾上腺素、血管加压素和血管紧张素均升高Km和Vmax。Ca2+内流有人提出，激素增加Ca2+易位率通过一个共同的Ca2+通道池，而不改变可用通道的数量或它们对Ca2+的亲和力。
The effects of the Ca2+-mobilizing hormones noradrenaline, vasopressin and angiotensin on the unidirectional influx of Ca2+ were investigated in isolated rat liver cells by measuring the initial rate of 45Ca2+ uptake. The three hormones increased Ca2+ influx, with EC50 values (concentrations giving half-maximal effect) of 0.15 microM, 0.44 nM and 0.8 nM for noradrenaline, vasopressin and angiotensin respectively. The actions of noradrenaline and angiotensin were evident within seconds after their addition to the cells, whereas the increase in Ca2+ influx initiated by vasopressin was slightly delayed (by 5-15s). The activation of Ca2+ influx was maintained as long as the receptor was occupied by the hormone. The measurement of the resting and hormone-stimulated Ca2+ influxes at different external Ca2+ concentrations revealed Michaelis-Menten-type kinetics compatible with a saturable channel model. Noradrenaline, vasopressin and angiotensin increased both Km and Vmax. of Ca2+ influx. It is proposed that the hormones increase the rate of translocation of Ca2+ through a common pool of Ca2+ channels without changing the number of available channels or their affinity for Ca2+.