Effect of hormones on transcription of the gene for cytosolic phosphoenolpyruvate carboxykinase (GTP) in rat kidney

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Abstract
The effect of hormones on the transcription rate of cytosolic phosphoenolpyruvate carboxykinase and level of mRNA for this enzyme in the rat kidney were investigated. In renal nuclei isolated from rats given dibutyryladenosine cyclic 3'',5''-phosphate (Bt2-cAMP) or 8-bromoadenosine cyclic 3'',5''-phosphate (8-Br-cAMP), [32P]UMP incorporation into hybridizable phosphoenolpyuvate carboxykinase mRNA increased several-fold within 1 h. Changes in the concentration of cytosolic phosphoenolpyruvate carboxykinase mRNA, measured by hybridization of [32P] c[complementary]DNA to poly(A+) mRNA, paralleled alterations in the transciption rate. Dexamethasone treatment of adrenalectomized rats increased the transcription rate and the level of phosphoenolpyruvate carboxykinase mRNA 3- to 4-fold after 4 h. Both parameters then declined to control values by 8 h. When dexamethasone (5 mg/kg) and Bt2cAMP (25 mg/kg) were given together, the rate of phosphoenolpyruvate carboxykinase RNA synthesis and the level of cystosolic mRNA were not increased more than those with either drug alone. Transcription of the gene for renal phosphoenolpyruvate carboxykinase was not affected by diabetes or glucose refeeding but was increased 2-fold after 24 h of starvation and reduced by bicarbonate feeding after 2 h. Glucocorticoids and cAMP change the rate of transcription of the phosphoenolpyruvate carboxykinase gene in rat kidney, leading to changes of similar magnitude in mRNA level and, hence, enzyme activity. The results presented here and in previous work indicate that the transcription rate of the gene for phosphoenolpyruvate carboxykinase in liver and kidney responds to hormones in a tissue-specific manner.