Gluconeogenesis in rat liver parenchymal cells in primary culture: permissive effect of the glucocorticoids on glucagon stimulation of gluconeogenesis.

Abstract

Primary cultures of parenchymal cells isolated from adult rat liver by a collagenase perfusion procedure and maintained as a monolayer in a serum-free culture medium were used to study gluconeogenesis and the role that the glucocorticoids play in the control of this pathway. These cells carried out gluconeogenesis from three-carbon precursors (alanine and lactate) in response to glucagon and dexamethasone added alone or in combination. Maximum glucose production was observed with cells pretreated for several hours with dexamethasone and glucagon prior to addition of substrate and glucagon (8- to 12-fold increase over basal glucose production). Half-maximum stimulation of gluconeogenesis was seen with 3.6 X 10(-10) M glucagon and 3.6 X 10(-8) M dexamethasone. Maximum stimulation was observed with 10(-7) M glucagon and 10(-6) M dexamethasone. The length of time of dexamethasone pretreatment was found to be important in demonstrating the effect of glucocorticoids on glucagon-stimulated gluconeogenesis. Treatment of cells with dexamethasone for 2 hours did not result in an increase in glucose production over identical experimental conditions in the absence of dexamethasone, whereas pretreatment for 5 hours (1.2-fold increase) or 15 hours (1.7-fold increase) did result in an increase in glucose production. The results establish that the adult rat liver parenchymal cells in primary culture are a valid model system to study hepatic gluconeogenesis. In addition, we have established directly that the glucocorticoids amplify the glucagon stimulation of gluconeogenesis.