RNA Polymerase Stimulation: Effect of Aldosterone and Other Adrenocorticoids on RNA Turnover in Rat Kidney

Abstract

The results of steroid hormone stimulation of aggregate RNA polymerase activity in kidney can be interpreted in terms of either template or enzyme alterations. In order to discover the effect of aldosterone on enzyme or DNA template, the RNA polymerases were purified from kidney nuclei of normal, adrenalectomized or adrenalectomized plus aldosterone treated rats and the activity was determined using different sources of DNA. It was found that the DNA from aldosterone treated rats was transcribed more efficiently than from other sources. Aldosterone does not seem to have a direct effect on the RNA polymerase. Fractionation of ([14C]aldosterone injected) kidney chromatin revealed the presence of radioactivity in the non-histone acidic proteins and DNA, suggesting the possible binding of aldosterone or aldosterone–receptor complex to these chromatin fractions which may result in enhanced template activity.Turnover of RNA was also studied in various subcellular fractions: nuclei, mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, polysomes, ribosomes and sRNA, in normal, adrenalectomized, and adrenalectomized plus adrenocortical hormone treated rat kidney, by following the loss of radioactivity after a single injection of [14C]-orotic acid. Daily administration of aldosterone or deoxycorticosterone reversed the effects of adrenalectomy. Daily administration of corticosterone was without effect.