RENAL TRANSPORT AND METABOLISM OF PROTEINS

拟议的研究旨在获取有关定量研究的信息 肾小管吸收与肾代谢的研究进展 蛋白质和多肽激素。分离的灌流大鼠肾脏将被 用于测定：a)低分子量蛋白质的浓度 在肾小球滤过液中，因此滤过的负荷和肾小管吸收 速率，b)小管吸收的动力学，包括其容量， 抑制剂的亲和力、特异性、选择性和效果以及c) 吸附蛋白的胞内水解动力学及其性质 由此产生的代谢物。一种无滤过的大鼠离体肾灌流模型 模型将被用来研究肾小球周围激素的代谢， 尤其是甲状旁腺激素(PTH)。在这项研究中，试图 将确定：a)PTH与其相互作用的动力学 肾小管周侧的受体和b)大约的分子量， 鼠源代谢物的抗原性和生物活性 甲状旁腺激素肾小管周围积水。使用隔离的灌流近端 兔曲管，我们将研究其动力学和机制。 对白蛋白的管状吸收的研究，目的是确定：a) 白蛋白的管状吸收最大值(Tm)，b)接触的影响 时间、液体重吸收以及代谢和内吞作用的抑制物 白蛋白的管状吸收，以及c)净电荷的影响 白蛋白对其肾小管吸收率的影响。在所有这些研究中，一种新的 高比活度氚标记蛋白质的方法 在不改变其结构、抗原性和生物活性的情况下 分子将被使用。希望这一结果将有助于阐明 肾脏在周转、调节血浆水平和代谢方面的作用 蛋白质和多肽激素的转化及其机制 牵涉其中。此外，获得的信息可能会提供新的见解 深入到蛋白尿的病理生理学，并对 对肾功能衰竭时激素失衡的理解。

The proposed research is aimed at acquiring information on the quantitative aspects and mechanisms of tubular absorption and renal metabolism of proteins and peptide hormones. The isolated perfused rat kidney will be used to determine: a) the concentration of low molecular weight proteins in the glomerular filtrate and hence filtered loads andtubular absorption rates, b) the kinetics of tubular absorption, including its capacity, affinity, specificity, selectivity and effect of inhibitors and c) the kinetics of intracellular hydrolysis of absorbed proteins and the nature of th resulting metabolites. A non-filtering isolated perfused rat kidney model will be used to study peritubular metabolism of pepetide hormones, particularly that of parathyroid hormone (PTH). In this study, attempts will be made to determine: a) the kinetics of interaction of PTH with its receptors at the peritubular side and b) the approximate molecular weights, antigenicity and biological activity of metabolites originating from the peritubular hy drolysis of PTH. Using the isolated perfused proximal convoluted tubule of the rabbit, we will study the kinetics and mechanisms of tubular absorption of albumin with the aim of determining: a) the tubular absorption maximum (TM) of albumin, b) the influence of contact time, fluid reabsorption, and inhibitors of metabolism and endocytosis on tubular absorption of albumin, and c) the influence of net charge of albumin on its tubular absorption rates. In all of these studies a new metod of labelling proteins with tritium to very high specific activity without changes in structure, antigenicity and biological activity of the molecules will be used. Hopefully, the results will elucidate the role of the kidney in the turnover, regulation of plasma levels, and metabolic transformations of proteins and peptide hormones and the mechanisms involved. In addition, the information acquired may provide new insights into the pathophysiology of proteinurias and contribute to the understanding of hormonal imbalances in renal failure.