Regulatory mechanisms of renal hemodynamics at the basis of arteriolar level.

肾循环由两条阻力血管--传入小动脉和传出小动脉调节。每条小动脉对内源性和外源性血管活性物质的不同反应调节肾血流量(RBF)和肾小球滤过率(GFR)。本研究通过体内和体外实验，确定腺苷(Ad)、胰升糖素(Gl)和乙酰胆碱(ACh)的作用部位和犬肾传入小动脉的性质。1)体内实验：在正常肾动脉压(RAP)时，上述药物均能增加RBF。Gl增加GFR，Ad降低GFR，ACh不影响GFR。Gl对RBF的增加仅发生在RAP的自动调节压力范围内，并且肾脏的自动调节能力减弱。相反，在自动调节压力范围内和之下，Ad都增加了RAP时的RBF，而自动调节能力并没有受到明显的损害。ACH完全废除了…对RBF进行更多的自动调节。一般认为，传入小动脉阻力在RAP时达到最小值，接近自动调节压力范围的下限。因此，这些数据表明，Gl和Ad分别优先扩张传入小动脉和传出小动脉，ACh则扩张两个小动脉。2)体外实验：cAMP(CAMP)作为激素或药物引起的血管扩张的第二信使的作用已被提出。细胞内cAMP浓度的升高被认为与某些药物对血管平滑肌的松弛有关。然后，探讨了腺苷环化酶强激动剂Forsklin(Fo)引起的cAMP积聚与传入小动脉扩张的关系。FO(10^&lt；-6&gt；M)扩张用去甲肾上腺素预先构建的分离的传入小动脉。与对照相比，FO(10^&lt；-5&gt；M)使cAMP产量增加10倍。因此，传入小动脉扩张与cAMP积聚密切相关。较少

Renal circulation are regulated by two resistance vessels, the afferent and the efferent arterioles. Different reactions of each arteriole to endogeneous and exogenous vasoactive agents regulate renal blood flow(RBF) and glomerular filtration rate(GFR). In the present research project, the in vivo and in vitro experiments were performed to determine the sites of action of adenosine(Ad), glucagon(Gl) and acetylcholine(ACh) and the nature of an afferent arteriole isolated from the canine kidney.1) in vivo experiments: At normal renal arterial pressure(RAP), RBF was increased by the above all agents. But, GFR was increased by Gl, decreased by Ad and unchanged by ACh. The increase in RBF by Gl occurred only at RAPs within the autoregulatory pressure range, and renal autoregulatory capability was attenuated. Contrary, Ad increased RBF at RAPs both within and below the autoregulatory pressure range, and the autoregulatory capability was not perceptibly impaired. ACh completely abolished the … More autoregulation of RBF. It is generally accepted that afferent arteriolar resistance attains a minimum value at RAP near the lower limit of the autoregulatory pressure range. Thus, these data indicate that Gl and Ad preferentially dilate the afferent arteriole and the efferent arteriole, respectively, and that ACh dilates both arterioles.2) in vitro experiments: The role of cyclic AMP(cAMP) as a second messenger of hormone or drug induced vasodilation has been proposed. A rise in intracellular cAMP concentration has been believed to be responsible for the relaxation of vascular smooth muscle by certain drugs. Then, the relationship between the dilation of isolated afferent arteriole and the cAMP accumulation induced by forskolin(Fo), a potent stimulator of adenylate cyclase. Fo(10^<-6> M) dilates the isolated afferent arteriole preconstructed with norepinephrine. Fo(10^<-5> M) produced 10-fold increase in cAMP production compared with control. Thus, the close relationship between the dilation of afferent arteriole and the cAMP accumulation. Less