Hutchinson J H, Porter G A
Physiol Chem Phys. 1975;7(5):453-64.
Demonstration of increased nuclear RNA specific radioactivity in epithelial cells scraped from isolated toad urinary bladder after brief treatment with aldosterone is shown to depend on the quantity of exogenous uridine supplied. By comparing the rate of incorporation of the nucleoside [6-3H] uridine into nuclear RNA at two different exogenous uridine concentrations, an estimate of the relative contribution of exogenous and endogenous nucleoside to the intracellular precursor pool was obtained. Based upon such an experimental model, we found that aldosterone significantly increased the contribution from endogenous precursor and conclude that one effect of the steroid in this isolated tissue is to accelerate RNA turnover. Accelerated RNA turnover, resulting from hormone treatment, was further substantiated by demonstarting a significant decrease in [6-3H] uridine concentration of the precursor pool of prelabeled cells following unlabeled uridine chase. Although evaluated, no evidence for aldosterone increasing the uptake of [6-3H] uridine into the acid-soluble precursor pool was found. In addition, the uridine concentration was shown not to be a rate-limiting step for the bioelectric demonstration of aldosterone-stimulated active Na+ transport.
用醛固酮短暂处理分离的蟾蜍膀胱后，刮取的上皮细胞中核RNA比放射性增加的现象表明，这取决于所提供的外源性尿苷的量。通过比较在两种不同外源性尿苷浓度下核苷[6-³H]尿苷掺入核RNA的速率，获得了外源性和内源性核苷对细胞内前体池相对贡献的估计值。基于这样一个实验模型，我们发现醛固酮显著增加了内源性前体的贡献，并得出结论，该类固醇在这个分离组织中的一个作用是加速RNA周转。激素处理导致的RNA周转加速，通过在未标记尿苷追踪后，预标记细胞的前体池中[6-³H]尿苷浓度显著降低得到进一步证实。尽管进行了评估，但未发现醛固酮增加[6-³H]尿苷摄取到酸溶性前体池的证据。此外，尿苷浓度并非醛固酮刺激的主动Na⁺转运生物电表现的限速步骤。
