Establishment of screening systems for evaluating drug actions in the kidney

L.肾单位异质性的特征支持了肾脏药物作用评价的筛选系统，所获得的结果包括肾单位能量代谢、嘌呤代谢酶的定位、cAMP对肾小球中超氧化物生成的抑制作用、血管紧张素I对早期近曲小管胞浆钙瞬变的双相增加作用、近曲小管中的一种新的加压素受体、甘氨酸抗生物素蛋白转移酶在肾脏内的定位，大鼠肾单位节段中的脂质过氧化，以及大鼠肾内蛋白质的处理。肾内产生PGE2的位点是高度异质的，袢利尿剂选择性地增加了在粗的上行支中的PGE2聚集，这表明PGE2是引起利尿的可能的生理介质。速尿也作用于下行细肢短袢，但不作用于离子袢，这可通过测定ATP周转率得出结论 关于我们 使用分离的肾单位片段。抗肾上腺素药物加强腺苷对肾小球的作用，这与抑制自由基形成密切相关。肾内脂质过氧化反应的评估使早期近端小管作为糖尿病肾病早期的致病部位成为可能。蛙膀胱可用于鉴定肾脏药物作用的细胞内机制，尤其是钠离子转运与蛋白激酶C偶联的机制。评价肾毒性的筛选系统细胞内ATP周转和激动剂诱导的胞浆游离钙瞬变是量化肾毒性沿着肾单位的敏感和有用的决定因素。代谢功能如肾再生和产氨作用可在组织学改变之前发现肾毒性的早期征象，这不仅可将肾作用药物和肾毒性药物分类，而且为更好地理解这些药物作用的机理提供了重要信息。少

l. Characteristies of nephron heterogeneity supporting screening systems tor the evaluation of renal drug actions.The results obtained include nephron energy metabolism, localization of purine-metabolizing enzymes, inhibitory effect of CAMP on superoxide generation in gloseruli, biphasic increasing effect of angiotensin I]on cytosolic calcium transient in early proximal tubule, a novel vasopressin receptor in the proximal tubule, localization of glycine avidinotransferase within the kidney, lipid peroxidation in rat nephron segments, and intrarenal handling of proteins in rats.2. Screening systems for the evaluation of kidney-acting drugs.Intrarenal sites of PGE2 production are highly heterogeneous, and loop diuretics increase PGE2 accuiu'ation selectively in the thick ascending limb suggesting PGE2 as a possible physiological mediator to cause diuresis. Furosemide also acts on short loop of descending thin limb, but not on Ions loop, that could be concluded by determining ATP turnover … More using isolated nephron seg2ents. Antinephrotic drugs potentiate adenosine action on glo2eruli which is well correlated with 'suppressive effect on free radical formation. Estimation of intranephron lipid peroxidation makes it possible to identify the early proximal tubule as a causative site of early stage in diabetic nephropathy. Frog urinary bladde can be used to identify intra cellular nechanislis of renal drug action especially on sodium ion transport coupled with protein kinase C.3. Screening systems for the evaluation of nephrotoxicity.Intracellular ATP turnover and agonist-induced cytosolic free calcium transients are sensitive and useful determinants to quantify nephrotoxicity along the nephron. Metabolic functions such as renal gluconeogenesis and ammoniagenesis can be used to find very early signs of nephrotoxicity prior to histological alterations.The above-summarized results can not only classify kidney-acting and nephrotoxic drugs, but also bring notable informations for the better understanding nechanisums of these drug actions. Less