垂体在刺激脑内渗透压感受器引起的肾脏反应中的作用

ROLE OF THE HYPOPHYSIS IN THE RENAL RESPONSES UPON STIMULATION OF THE BRAIN OSMORECEPTOR

实验在α氯醛糖和氨基甲酸乙酯混合麻醉的大鼠中进行。脑室内注射高张盐水(icv.HS)后,肾血浆流量、肾小球滤过率、尿量、尿钠排出量、尿钾排出量和渗透物质清除率均增加,游离水清除率下降。去除垂体后,icv.HS不再能引起上述肾脏反应。另外给大鼠静脉注射血管升压素(VP)拮抗剂(V_1和V_2受体拮抗剂),并不能削弱上述icv.HS引起的肾脏反应。脑室内注射高张盐水后,尿中多巴胺(DA)排出量无显著增多;给予多巴脱羧酶抑制剂苄丝肼也不能削弱icv.HS引起的肾脏反应。上述实验结果表明,在本实验条件下刺激脑内渗透压感受器引起的肾脏反应依赖于垂体的完整性,但看来并不依赖于外周的VP和DA,故垂体通过何种机制介导icv.HS引起上述肾脏反应,有待于进一步的研究。

The experiments were performed in rats anaesthetized with α-chloraloseand urethane. Intracerebroventricular administration of hypertonic saline (icv.HS) resulted in an increase in renal plasma flow rate, glomerular filtration rate.urine flow rate, urinary sodium excretion, urinary potassium excretion, and os-molar clearance, and a decrease in free water clearance. These responses wereabolished in hypophysectomized rats, but were not significantly affected by intrave-nous injection of vasopressin (VP) receptor (V_1 and V_2) antagonist. The urinarydopamine (DA) excretion did not change significantly after icv. HS. Moreover,administration of benserazide, an inhibitor of the enzyme L-aromatic amino aciddecarboxylase that converts L-dopa to DA, did not attenuate the diuresis and na-triuresis induced by icv. HS. These results suggest that the renal responses uponstimulation of the brain osmoreceptor are dependent on the integrity of the hy-pophysis, while the VP and DA are not essential to these renal responses. Thehypophysial factors responsible for the icv. HS-induced renal responses remainto be explored.