The effect of steroids and ammonium chloride acidosis on phosphoenolpyruvate carboxykinase in rat kidney cortex. II. The kinetics of enzyme induction.

The kinetics of the induction of rat kidney phosphoenolpyruvate carboxykinase activity after triamcinolone and ammonium chloride administration have been investigated with a view to the further differentiation of the two processes. The half-life of kidney phosphoenolpyruvate carboxykinase activity, as measured from the decay curve after a single doses of triamcinolone, is approximately 1.4 hr. This compares with a half-life for the enzyme from acidotic kidney of approximately 3.4 hr. Analysis of the data indicates that the induction of phosphoenolpyruvate carboxykinase activity by triamcinolone may be attributed to an increase in de novo protein synthesis. Induction by acidosis is qualitatively distinct and is partly attributed to a reduction in the rate of decay of phosphoenolpyruvate carboxykinase activity. The activities of the gluconeogenic enzymes glucose-6-phosphatase, fructose-1,6-diphosphatase, and phosphoenolpyruvate carboxykinase in both liver and kidney have been measured in animals separately treated with triamcinolone and ammonium chloride. Triamcinolone significantly increases the activities of liver phosphoenolpyruvate carboxykinase, kidney glucose-6-phosphatase, and kidney phosphoenolpyruvate carboxykinase only; ammonium chloride stimulates a 200% increase in kidney phosphoenolpyruvate carboxykinase, but has no effect on the other enzymes. The induction processes whereby triamcinolone increases phosphoenolpyruvate carboxykinase activities in liver and kidney differ quantitatively.