Factors affecting the synthesis of RNA from exogenous precursors in rat kidney

Kalra, Jawahar (1972) Factors affecting the synthesis of RNA from exogenous precursors in rat kidney. Masters thesis, Memorial University of Newfoundland.

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Abstract

The effect of adrenalectomy and corticosteroid administration on precursor uptake and RNA synthesis in rat kidney was studied. A number of radioactively labeled precursors (³H-uridine, ³H-cytidine, and ¹⁴C-orotic acid) were used to determine the time course of incorporation into the acid soluble pool and the alkaline hydrolyzate fractions of both the normal and adrenalectomized rats. The incorporation of these precursors into both RNA and acid soluble pool was linear for at least 20 minutes. -- A general decrease in the rate of incorporation of ³H-cytidine and ¹⁴C-orotic acid into the alkaline hydrolyzate fraction of kidneys was observed 7 to 8 days after adrenalectomy as compared to normal animals. Administration of a single dose of aldosterone 1 or 2 hours prior to the isotope, increased the rate of incorporation into acid soluble pool as well as into the alkaline hydrolyzate fraction to a level greater than that in normal rats. Actinomycin D administration 2 hours prior to the ¹⁴C-orotic acid markedly decreased RNA synthesis,but had no significant effect on the uptake of precursor into the acid soluble pool. Actinomycin D plus aldosterone treatment, compared to actinomycin D alone, resulted in an increase in precursor uptake into the acid soluble pool. -- These studies suggest that most of the stimulatory effect of aldosterone on the incorporation of exogenous precursor into RNA of rat kidney is attributable to an increase in the rate of precursor uptake. There may also be a genuine stimulation of RNA synthesis as aldosterone increases the RNA:DNA ratio of adrenalectomized rat kidneys to the levels of normal animals. -- The effects of single injections of deoxycorticosterone, corticosterone and cortisol on the incorporation of ¹⁴C-orotic acid into the kidneys of adrenalectomized rats were also studied. Deoxycorticosterone, corticosterone stimulated the precursor incorporation into acid soluble pool but no effect was observed on the incorporation into the alkaline hydrolyzate fraction. On the other hand, cortisol administration caused a decrease in the incorporation of precursor into the alkaline hydrolyzate fraction without affecting precursor incorporation into the acid soluble pool, suggesting that it may decrease RNA synthesis in the kidneys of adrenalectomized rats.

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