Bryant H N, Perks A M
J Dev Physiol. 1982 Apr;4(2):139-51.
Melanocyte-stimulating activity in the pituitary and plasma of fetal, newborn and adult guinea-pigs, and in amniotic fluid, was bioassayed on isolated Anolis skin. In the fetuses, levels in the posterior, anterior and whole pituitary increased exponentially between 39 and 70 days of gestation; in all cases, the increases were close to 35-fold in terms of ng/lobe, and 6-fold in ng/mg of lyophilized tissue. The increases were due to growth, and to an increased accumulation within the tissues. Ratios of activity in the posterior pituitary: anterior pituitary: hypothalamus approximated 200:30:1 (ng/mg of dry tissue). Fetal plasma levels showed some scatter; however, there were no trends with age, and the average value (10.0 +/- 1.6 ng/ml) was close to that of the mothers (10.6 +/- 2.6 ng/ml). Plasma activity appeared to fall markedly around birth; newborn pups, 2-6 hours after birth, showed levels 65% below those of the fetuses, and also below those of the adults (significant; P less than 0.05). At the same time the pituitary levels increased; this suggested a shut-down in release. The possible implications of this in the birth processes are discussed. Amniotic fluid showed only low, inconsistent activity, below 1% of plasma levels.
利用离体的安乐蜥皮肤对豚鼠胎儿、新生豚鼠及成年豚鼠的垂体、血浆以及羊水的促黑素细胞活性进行了生物测定。在胎儿中，妊娠39至70天期间，垂体后叶、垂体前叶及整个垂体中的活性呈指数增长；在所有情况下，以每叶纳克计算，增长接近35倍，以每毫克冻干组织纳克计算，增长6倍。这种增长是由于生长以及组织内积累增加所致。垂体后叶、垂体前叶及下丘脑的活性比值约为200:30:1（每毫克干组织纳克）。胎儿血浆水平存在一定离散度；然而，没有随年龄变化的趋势，平均值（10.0±1.6纳克/毫升）与母体平均值（10.6±2.6纳克/毫升）相近。血浆活性在出生前后似乎显著下降；新生幼崽出生后2至6小时的水平比胎儿低65%，也低于成年豚鼠（具有显著性；P<0.05）。与此同时，垂体水平升高；这表明释放停止。文中讨论了这一现象在出生过程中的可能影响。羊水仅显示出低且不稳定的活性，低于血浆水平的1%。
