Reversible inhibition of the norepinephrine induction of lactate dehydrogenase by cytochalasin B in rat glial C6 cells.

The cyclic AMP mediated induction of lactate dehydrogenase (LDH: E.C. 1.1.1.27) activity by norepinephrine in the rat glial cell line C6 is inhibited by cytochalasin B. Doses of 5, 15, and 25 microgram/ml of cytochalasin B inhibited the induction equally. Twenty-five microgram/ml of cytochalasin B inhibited the induction reversibly, and had no effect on basal enzyme level. No effect of cytochalasin B on general protein synthesis was found, nor did it increase the rate of decline of enzyme activity in deinduced cells. It therefore appears to block LDH induction by selectivity inhibiting its synthesis. Cytochalasin B had no effect on the transient (intracellular and extracelllular) rise in cyclic AMP generated in response to norepinephrine treatment. Cytochalasin B was effective when added during the transcription dependent phase (first 3 hours) but not during the translation dependent phase (after 3 hours) of LDH induction. The suggestion is discussed that cytochalasin B inhibits one of the early events of the inductive process.