Richardson S B, Twente S
Department of Medicine, Veterans Administration, New York, New York 10010.
J Endocrinol. 1991 Jan;128(1):91-5. doi: 10.1677/joe.0.1280091.
The precise roles of GH-releasing factor (GRF) and somatostatin (SRIF) in the orchestration of pulsatile GH secretion have not yet been fully determined. We examined the interactions of rat GRF and SRIF in the concentration ranges present in rat hypophysial-portal blood, on the secretion of GH from dispersed male rat anterior pituitary cells in monolayer culture. The effects of exposing cells to GRF and/or SRIF (0.01-1.nmol/l) for 1 h were compared with the effects of preincubation of cells with SRIF before experimental incubations. As anticipated, the stimulatory effects of 0.1-1 nmol GRF/1 were abolished by concurrent incubation with SRIF at an equimolar concentration, although SRIF, at these concentrations, did not significantly inhibit basal GH secretion. Conversely, pre-exposure to 0.1 nmol SRIF/1 for 30 or 60 min, resulted in an increase in GH secretion during a subsequent 60-min incubation period, both in the absence or in the presence of GRF (0.01-1 nmol/l). Pretreatment with GRF caused increased responsivity to GRF rather than significant sensitization of the GH response to GRF. These observations demonstrate actions of SRIF, at low and probably physiological concentrations, which are more complex than those of a pure inhibitor of GH secretion. Pre-exposure of the pituitary to SRIF enhances subsequent GH secretion, suggesting that SRIF may play an additional physiological role in amplifying the GRF signal.
生长激素释放因子（GRF）和生长抑素（SRIF）在调节生长激素脉冲式分泌中的确切作用尚未完全明确。我们研究了大鼠GRF和SRIF在大鼠垂体门脉血中的浓度范围内，对单层培养的分散雄性大鼠垂体前叶细胞分泌生长激素的相互作用。将细胞暴露于GRF和/或SRIF（0.01 - 1 nmol/L）1小时的效果与在实验孵育前用SRIF预孵育细胞的效果进行了比较。正如预期的那样，0.1 - 1 nmol GRF/1的刺激作用在与等摩尔浓度的SRIF同时孵育时被消除，尽管在这些浓度下，SRIF并未显著抑制基础生长激素分泌。相反，预先暴露于0.1 nmol SRIF/1 30或60分钟，在随后60分钟的孵育期内，无论有无GRF（0.01 - 1 nmol/L），生长激素分泌都会增加。用GRF预处理会导致对GRF的反应性增加，而不是对GRF的生长激素反应显著致敏。这些观察结果表明，在低浓度且可能是生理浓度下，SRIF的作用比单纯的生长激素分泌抑制剂更为复杂。垂体预先暴露于SRIF可增强随后的生长激素分泌，这表明SRIF可能在放大GRF信号方面发挥额外的生理作用。
