THE ACTION OF ADRENOCORTICOTROPHIN ON THE FREE NUCLEOTIDE POOL AND RNA SYNTHESIS IN RAT ADRENALS AND LIVER

Abstract

SUMMARY The action of adrenocorticotrophin (ACTH) in vivo on the amount and [32P]phosphate labelling of free adenine nucleotides and RNA of rat liver and adrenals was studied. Treatment with ACTH did not alter the total amount of free adenine nucleotides. In both the liver and adrenals the amount of ATP decreased, while that of ADP and AMP increased. As a result a more than twofold decrease of the ATP: ADP + AMP ratio was caused by ACTH. This effect was observed 2 h after ACTH administration and remained unchanged up to the 24th hour. Three hours after [32P]phosphate administration, the labelling of the α-phosphate of free adenine nucleotides in liver was more than five times higher than that in the adrenals. After 24 h of treatment with ACTH the incorporation of [32P]phosphate into free adenine nucleotides of the adrenal was decreased, while that of liver was increased. The labelling of the high-molecular weight RNA of the adrenals and liver was of the same order. A similar correlation was found when the labelling of AMP obtained from RNA by snake venom phosphodiesterase hydrolysis was compared. Treatment with ACTH decreased the labelling of RNA in the adrenals, while the labelling of RNA in liver was increased. The changes in the labelling of RNA in both organs reflect the variations in the labelling of free adenine nucleotides. The results are discussed and it is suggested that ACTH treatment in vivo affects the amount and the turnover of free nucleotides in the adrenals and liver. The variations in RNA labelling are secondary and reflect the turnover of the free nucleotides.