Eur. J. Biochem. 26 (1972) zyxwvuts 543-552 Effects of Aldosterone and Other Steroids zyxw in zyx vivo on Rat-Kidney Cortex Alterations in Translation by Isolated Ribosomes and in the Thiol Content of Nuclear Proteins Daniel TRACHEWSKY, Adhip. P. NANDI MAJUMDAR, and L. Fernando CONGOTE Laboratoire de Biologie Moleculaire de I’Institut de Recherche5 Cliniques de Montreal (Received April 15/December 2, 1971) An investigation of the effects of aldosterone, deoxycorticosterone, Sol-fluorocortisol, and 178- estradiol administration, respectively, to adrenalectomized male rats on the polypeptide synthesis by and poly(U)-directed binding of phenylalanyl-tRNA to isolated renal cortical ribosomes has revealed several interesting facts. As well as causing an increase in the ability of the ribosomes to synthesize polyphenylalanine in the presence of poly(U), the three mineralcorticoids also in- creased the poly(U)-directed binding of phenylalanyl-tRNA to the ribosomes. 17/?-Estradiol treatment, however, caused a decrease in the ability of the ribosomes to incorporate phenyl- alanine into polyphenylalanine when compared to the untreated controls. There were also no significant differences in the amount of poly(U)-directed binding of phenylalanyl-tRNA to the ribosomes of the estrogen-treated rats when compared to the untreated animals. Consequently, it was concluded that all four steroids had induced some alterations in the properties of the renal cortical ribosomes. The effect of aldosterone and 17,5-estradiol on the thiol content of the nuclear proteins from rat kidney cortex showed an interesting correlation with the translational effects of both steroids. Thus aldosterone increased, and 178-estradiol slightly decreased, the thiol content of these pro- teins, measured as the incorporation of radioactive iodoacetate in whole nuclei in vitro. Under the experimental conditions used, the reaction was especially concentrated in discrete protein fractions of molecular weights of about 14000 and 42000. The effect of the hormones on the thiol content was not specifically concentrated in any of these protein fractions. In the last few years, the results of a variety of physiological and biochemical studies on the isolated toad bladder system and the kidney of the adrenal- ectomized rat have suggested that aldosterone regu- lates active sodium transport by zyxwvuts de novo synthesis of proteins induced by stimulation of DNA-depen- dent RNA synthesis [l-71. Some more recent ex- periments have shown no effect on protein biosyn- thesis in vivo after aldosterone stimulation zyxwvu [8] while other results are consistent with a mineralocorticoid effect on protein synthesis [9]. Consequently, little was known about the effect of aldosterone on the translational process of gene expression until re- cently when it was reported that aldosterone ad- Abbreviation and Trivial Names. Poly(U), polyuridylic acid; aldosterone, 18,ll-hemiacetal of llg,2l-dihydroxy- 3,20-dioxo-4-pregnen-lS-al; 9a-fluorocortisol, 9a-fluoro- llj3,17,2l,trihydroxy-4-pregnene-3,20-dione; deoxycortico- sterone, 21-hydroxy-4-pregnene-3,20-dione; 17p-estradio1, 1,3,5( lO)-estratriene-3,17~-dioI. Enzymes. Yeast alcohol dehydrogenase (EC 1.1.1.1); catalase (EC 1.11.1.6); pancreatic ribonuclease (EC 2.7.7.16). ministration to bilaterally adrenalectomized rats resulted in an increase in the ability of the isolated renal cortical ribosomes to incorporate phenylalanine into polypeptide [lo, 111. The effects of several other steroids on the translational process by isolated rat kidney cortex ribosomes has also recently been de- scribed [lS]. In view of the recent hypothesis of hormone action at the site of the translational pro- cess [13], studies on a specific effect of mineralo- corticoids on the renal cortical cytoplasmic system are of considerable interest. We therefore have in- vestigated the changes in amino acid incorporation by, and aminoacyl-tRNA binding to, isolated ribo- somes from the kidney cortices of adrenalectomized rats after the administration in vivo of aldosterone, deoxycorticosterone, Sol-fluorocortisol,and 17B-estra- diol. We are equally interested in the relationship between early reactions in the cell nucleus and the translational effects of aldosterone. Two kinds of investigations have been pursued on this topic :