细胞外Ca^(2+)和K^+对鲤鱼脑垂体离体生长激素分泌的影响

EFFECTS OF EXTRACELLULAR CALCIUM AND POTASSIUM ON GROWTH HORMONE SECRETION FROM COMMON CARP PITUITARY IN VITRO

采用脑垂体离体灌流孵育系统,研究细胞外 Ca^(2+)和 K^+对鲤鱼脑垂体基础的和鲑鱼促性腺激素释放激素(sGnRH)刺激的生长激素(GH)分泌的影响。离体灌流孵育的鲤鱼脑垂体基础 GH分泌和 sGnRH 刺激的 GH 分泌都是细胞外 Ca^(2+)依赖的,缺细胞外 Ca^(2+)存在时,基础 GR分泌显著下降,2分钟脉冲式 sGnRH 刺激的 GH 分泌反应接近消失。Ca^(2+)通道阻滞剂异搏定以剂量依存形式显著抑制基础的和2分钟脉冲式sGnRH 刺激的 GH 分泌,表明细胞外 Ca^(2+)的作用至少部分通过细胞膜电位敏感性 Ca^(2+)通道。50mM K^+显著刺激基础GH 分泌,并显著加强高剂量sGnRH 刺激的GH 分泌,且K^+的作用是细胞外 Ca^(2+)依赖的。

The effects of extracellular Ca^(2+) and K^+ on the basal and salmonGnRH (sGnRH)-stimulated growth hormone (GH) release from pituitary of com-mon carp were studied using an in vitro perifusion system for pituitary fragmen-ts. The basal and sGnRH-stimulated GR secretion from erifused pituitary ofcommon carp were extracellular Ca^(2+)-dependent. In the absence of extracellularCa^(2+), the significant reduction in the basal GH secretion and almost disappearan-ce in the GH release responses to 2--min pulses of sGnRH (1, 10 and 100nM)were observed. Voltage-sensitive calcium channels (VSCC) antagonist verapam il(VER) significantly inhibited the basal GH release and CH release responses to2- min pulses of sGnRH (1,10 and 100nM) in a dose--dependent manner, indica-ting that the effects of extracellular Ca^(2+) on the basal and sGnRH-stimulated GHrelease are, at least partially, via the action of VSCC. 50mM K^+ significantlystimulated the basal GR release from perifused pituitary of common carp, andmarkedly potentiated the action of pulses of high dose of sGnRH (100nM) on GHsecretion. The effects of elevated K^+ were extracellular Ca^(2+)--dependent.