Ashiru O A, Rush M E, Blake C A
J Endocrinol. 1981 Jan;88(1):103-13. doi: 10.1677/joe.0.0880103.
The effects of exogenous rat LH or FSH on the release of endogenous FSH in the cyclic rat have been investigated. Rats were administered phenobarbitone to block the spontaneous increases in gonadotrophins in plasma during pro-oestrus and oestrus and then cannulated through the jugular vein or cannulated and hypophysectomized during the late morning or early afternoon of pro-oestrus. Comparison of patterns of plasma FSH in hypophysectomized and intact rats after i.v. injection of 0.5 micrograms FSH at 17.00 h suggested that exogenous FSH stimulated the release of endogenous FSH in less than 5 h. Intravenous LH (2 micrograms at 16.00 and at 18.00 h) raised the level of FSH in plasma between 2 and 6 h after the first injection of LH. Both gonadotrophins stimulated FSH release by the pituitary gland during the morning of oestrus. Comparison of patterns of plasma FSH in hypophysectomized and intact rats after i.v. injection of 0.25 or 0.05 micrograms FSH at 14.00 h suggested that the latency between FSH injection and stimulation of some FSH release by the pituitary gland is as short as 2 h. Intravenous LH (3, 4 or 9 micrograms) at 14.00 h did not increase the level of FSH in plasma within 2 h and was only minimally effective in raising the level within 4 h. Intravenous LH (2 micrograms at 16.00 and at 18.00 h) on the afternoon of dioestrus day 2 was nearly as effective in increasing the levels of FSH in plasma as it was when administered to pro-oestrous rats. This procedure did not raise the plasma levels of FSH in rats used on dioestrus day 1. The results suggest that in the phenobarbitone-blocked, pro-oestrous rat (1) a small increase (less than that observed spontaneously) in plasma rat FSH during pro-oestrus is effective in stimulating FSH release by the pituitary gland, (2) an increase in plasma rat FSH can exert positive feedback on its own secretion within 2 h and (3) a large increase in plasma rat LH is not very effective in increasing the plasma level of FSH over a period of 4 h. The results also suggest that the spontaneous increase in plasma levels of FSH and, to a lesser extent, of LH is involved in causing the selective phase of FSH release which occurs during late pro-oestrus and the morning of oestrus, and that LH and FSH act differently, but not necessarily by way of a different mechanism, to stimulate release of FSH by the pituitary gland.
研究了外源性大鼠促黄体生成素（LH）或促卵泡生成素（FSH）对处于发情周期大鼠内源性FSH释放的影响。给大鼠注射苯巴比妥，以阻断动情前期和发情期血浆中促性腺激素的自发升高，然后在动情前期的上午晚些时候或下午早些时候通过颈静脉插管，或插管并切除垂体。在17:00静脉注射0.5微克FSH后，比较切除垂体和完整大鼠的血浆FSH模式，结果表明外源性FSH在不到5小时内刺激了内源性FSH的释放。静脉注射LH（16:00和18:00各注射2微克）后，在首次注射LH后的2至6小时内，血浆中FSH水平升高。在发情期上午，两种促性腺激素均刺激垂体释放FSH。在14:00静脉注射0.25或0.05微克FSH后，比较切除垂体和完整大鼠的血浆FSH模式，结果表明FSH注射与垂体刺激某些FSH释放之间的延迟短至2小时。14:00静脉注射LH（3、4或9微克）在2小时内未增加血浆中FSH水平，在4小时内升高水平的效果也很微弱。在动情后期第2天下午静脉注射LH（16:00和18:00各注射2微克），增加血浆中FSH水平的效果与给动情前期大鼠注射时几乎相同。该操作未提高动情后期第1天所用大鼠的血浆FSH水平。结果表明，在苯巴比妥阻断的动情前期大鼠中：（1）动情前期血浆中大鼠FSH的小幅升高（低于自发观察到的升高幅度）可有效刺激垂体释放FSH；（2）血浆中大鼠FSH的升高可在2小时内对其自身分泌产生正反馈；（3）血浆中大鼠LH的大幅升高在4小时内增加血浆FSH水平的效果不太显著。结果还表明，血浆中FSH水平的自发升高以及程度较轻的LH水平的自发升高，参与了导致在动情后期晚期和发情期上午发生的FSH选择性释放阶段，并且LH和FSH以不同方式，但不一定通过不同机制，刺激垂体释放FSH。
