LHRH-A、DA对施氏鲟脑垂体碎片释放GtH的影响

为了探讨在古老的软骨硬鳞鱼中促性腺激素(GtH)的双重内分泌调节作用,本实验设计用离体灌流的方法研究促黄体素释放激素类似物(LHRH-A)和多巴胺(DA)对施氏鲟脑垂体碎片分泌GtH的影响。引入10、100和1 000 nmol/L 3个浓度的LHRH-A对施氏鲟脑垂体碎片3次脉冲式刺激实验;每次间隔1 h,持续5 min,研究不同剂量LHRH-A对鲟鱼脑垂体释放GtH的作用;用200 nmol/L DA对施氏鲟脑垂体碎片持续2 h灌流后引入5 min的1 000nmol/L LHRH-A刺激实验,研究DA如何抑制鲟鱼脑垂体释放GtH。每5 min收集一管灌流液,用放射免疫测定法(RIA)检测灌流液中GtH的含量。结果显示,低剂量LHRH-A随着刺激引入脑垂体释放GtH出现波浪式的增加,中、高剂量出现释放延后现象。LHRH-A在10nmol/L到1 000 nmol/L范围内对刺激脑垂体释放GtH没有剂量依存关系。DA对施氏鲟脑垂体碎片GtH的分泌没有显著影响,但是可以抑制LHRH-A引起的GtH分泌,即DA不能抑制施氏鲟GtH的基础分泌,而只能抑制LHRH-A诱导的GtH分泌。研究结果证明,在高等硬骨鱼类中存在的双重神经内分泌调节在古老的鲟鱼中也存在。

LHRH-A and DA effect on GtH release from pituitary fragments of Amur sturgeon(Acipenser schrenckii) in vitro

In order to study the dual endocrine effect on the gonadotropin release of pituitary in the ancient Chondrostei fish,luteinizing hormone releasing hormone analog(LHRH-A)and dopamine(DA)were used in vitro to research their effect on gonadotropin release of pituitary fragment in Amur sturgeon(A.schrenckii).Two experiments were designed to study how the LHRH-A and DA affect the GtH release of pituitary fragment:Three times repetitive pulse stimulation of 10,100 and 1 000 nmol/L different dosages of LHRH-A were introduced every one hour for five minutes,perfusion;And then after two hours,perfusion of 200 nmol/L DA,1 000 nmol/L LHRH-stimulation was introduced for five minutes.The perfusate was collected every five minutes to test the GtH content using Radio Immunoassay(RIA)method.The results showed that repetitive pulse administration of LHRH-A was able to be stimulating GtH release from the pituitary fragments in vitro in Amur sturgeon,without dose-dependent manner at the dosage from 10 nmol/L to 1 000 nmol/L.It seemed LHRH-A at high concentration restrained the release of GtH by itself.Dopamine(DA)had no obvious effect on basal GtH secretion of pituitary while it could restrain the GtH release of pituitary fragment induced by LHRH-A.It proved that dual endocrine regulation of GtH release also existed in sturgeon.