CATECHOLAMINE-MEDIATED ELEVATION OF CYCLIC-GMP IN RAT C-6 GLIOMA CELL LINE

Abstract

Catecholamines cause an elevation of both cyclic[c]GMP and cyclic[c]AMP levels in the rat C-6 glioma cell line. The response is mediated by a .beta.-receptor, with a Ka for stimulation of cGMP of 2.6 .times. 10-7 M. Maximum levels of cGMP are reached by 5 min, but cAMP levels are maximal by 10 min. Removal of Ca decreases the cGMP elevation by 60%. Refractoriness to a 2nd treatment with catecholamine develops for both responses. Catecholamine sensitivity of the cGMP-generating system appears in the cells only as they start to contact and enter the stationary growth phase. In contrast to the effects of catecholamines, cholinergic agonists have no effect on either cGMP or cAMP levels.