Bentley A M, Wallis M
Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Falmer, Brighton.
J Endocrinol. 1987 Oct;115(1):13-8. doi: 10.1677/joe.0.1150013.
The autoregulation of rat prolactin secretion at the level of the pituitary gland was investigated, using a static incubation system. The rate of prolactin secretion from the female anterior pituitary gland in vitro was found to be constant when the medium was changed at 20-min intervals. However, when the medium was left unchanged and secretory products were allowed to accumulate, prolactin secretion began to decline within 60 min. This effect was not observed with the male tissue, where the level of accumulated prolactin did not reach that at which the inhibition occurred using female tissue. The nature of the putative secretory product causing the inhibition of prolactin secretion was investigated. Exogenous bovine prolactin (1-4 mg/l) caused an inhibition of endogenous rat prolactin secretion. Inclusion of monoamine oxidase in unchanged medium, to prevent dopamine accumulation in the medium (a possible consequence of co-storage and co-secretion with prolactin granules), did not prevent the inhibition observed in the control incubation. We therefore conclude that in-vitro autoregulation of prolactin secretion can occur at the level of the pituitary gland, probably due to the accumulated prolactin having a feedback action on the lactotroph. This might be of physiological significance if localized concentrations of the hormone within the gland are high.
采用静态孵育系统研究了大鼠垂体水平催乳素分泌的自动调节。当每隔20分钟更换一次培养基时，发现体外雌性垂体前叶催乳素的分泌速率是恒定的。然而，当培养基保持不变且允许分泌产物积累时，催乳素分泌在60分钟内开始下降。在雄性组织中未观察到这种效应，雄性组织中积累的催乳素水平未达到使用雌性组织时发生抑制的水平。研究了导致催乳素分泌受抑制的假定分泌产物的性质。外源性牛催乳素（1 - 4毫克/升）会抑制内源性大鼠催乳素的分泌。在未更换的培养基中加入单胺氧化酶以防止多巴胺在培养基中积累（这可能是与催乳素颗粒共同储存和共同分泌的结果），并不能阻止在对照孵育中观察到的抑制作用。因此，我们得出结论，催乳素分泌的体外自动调节可能发生在垂体水平，这可能是由于积累的催乳素对催乳细胞具有反馈作用。如果腺体内激素的局部浓度较高，这可能具有生理意义。
