Dexamethasone effects on liver pyruvate kinase.

Dexamethasone in the medium perfusing isolated rabbit livers caused a fast-acting and reversible effect on liver pyruvate kinase. The effect was to lower the assayable V activity (units/g tissue) without changing the concentration (nmol/g enzyme protein). In effect, glucocorticoid lowered the specific activity (units/nmol of enzyme) by direct action on liver. The effect on liver pyruvate kinase is mediated by a relatively stable alteration; 30 min after perfusate (with steroid) was replaced by perfusate (without steroid), the effect remained strongly evident.