Effect of glucocorticoids on plasma cholinesterase in the rat.

Changes in plasma cholinesterase (ChE) activity after administration of glucocorticoids (prednisone, methyl-prednisolone and dexamethasone) were studied in male and female rats. The decrease of ChE activity-probably due to inhibition of ChE synthesis in the liver-was more marked in female than in male rats. This difference could be explained by the more rapid metabolism of glucocorticoids in male than in female rats or by the decreased stimulatory effect of estrogens on ChE synthesis after administration of glucocorticoids. The inhibitory effect of dexamethasone on ChE synthesis was significantly greater than the effect of equivalent antiinflammatory doses of the other two glucocorticoids investigated. The inhibitory effect of glucocorticoids on ChE activity increased with the duration of their administration. Decrease of ChE activity was more marked after the p.o. than after the i.p. route of application, indicating that inhibition of ChE synthesis after p.o. administration of glucocorticoids occurs partially during the first pass of these drugs in the liver.