Yu W H, Seeburg P H, Nikolics K, McCann S M
Department of Physiology, University of Texas Health Science Center, Dallas 75235.
Endocrinology. 1988 Jul;123(1):390-5. doi: 10.1210/endo-123-1-390.
The in vivo effects of GnRH-associated peptide (GAP) on PRL, LH, and FSH release have been examined by injecting this peptide iv into the following types of conscious rats: 1) ovariectomized steroid-blocked females, 2) ether-stressed males, and 3) lactating females. GAP (2.4 X 10(-10) and 2.4 X 10(-9) mol) suppressed plasma PRL release but did not affect the levels of plasma LH and FSH in ovariectomized steroid-blocked rats. Furthermore, with 1-min etherization, GAP (1.6 X 10(-10) and 8.0 X 10(-10) mol) reduced the stress-induced rise of plasma PRL, but had no effect on the stress-induced decline of plasma gonadotropin levels in male rats. A single iv injection of GAP (8.0 X 10(-10) mol) into lactating rats before the onset of nursing did not block the elevation of plasma PRL induced by suckling. However, a second injection of GAP (1.6 X 10(-10) mol) at 30 min after the onset of suckling partially lowered plasma PRL levels 15 min later. By contrast, plasma FSH levels were significantly elevated by the second injection of GAP, and plasma LH also rose after iv administration of GAP in the nursing rats. These results indicate that the activity of GAP to stimulate FSH and LH release is limited, since GAP stimulated the release of FSH and LH only when plasma gonadotropin levels were extremely low. However, the in vivo evidence that GAP inhibited PRL release in a variety of conditions reinforces the possibility that GAP could be the peptidic PRL-inhibiting factor.
通过向以下几种清醒大鼠静脉注射促性腺激素释放激素相关肽（GAP），研究了其对催乳素（PRL）、促黄体生成素（LH）和促卵泡生成素（FSH）释放的体内作用：1）去卵巢并用类固醇阻断的雌性大鼠；2）经乙醚应激的雄性大鼠；3）哺乳期雌性大鼠。在去卵巢并用类固醇阻断的大鼠中，GAP（2.4×10⁻¹⁰和2.4×10⁻⁹摩尔）可抑制血浆PRL释放，但不影响血浆LH和FSH水平。此外，在1分钟乙醚麻醉下，GAP（1.6×10⁻¹⁰和8.0×10⁻¹⁰摩尔）可降低应激诱导的雄性大鼠血浆PRL升高，但对应激诱导的血浆促性腺激素水平下降无影响。在哺乳开始前向哺乳期大鼠单次静脉注射GAP（8.0×10⁻¹⁰摩尔），不能阻断哺乳诱导的血浆PRL升高。然而，在哺乳开始后30分钟第二次注射GAP（1.6×10⁻¹⁰摩尔），15分钟后可部分降低血浆PRL水平。相比之下，第二次注射GAP可使哺乳期大鼠血浆FSH水平显著升高，静脉注射GAP后血浆LH也升高。这些结果表明，GAP刺激FSH和LH释放的活性有限，因为GAP仅在血浆促性腺激素水平极低时才刺激FSH和LH释放。然而，GAP在多种条件下抑制PRL释放的体内证据进一步支持了GAP可能是肽类PRL抑制因子的可能性。
