ANESTHETIC BARBITURATES ENHANCE G(S-ALPHA)-DEPENDENT CYCLIC-AMP PRODUCTION IN S49 MOUSE LYMPHOMA-CELLS

Cyclic AMP (cAMP) regulates many important physiological processes. Ba rbiturates influence cAMP regulation, possibly through effects on G pr oteins. This study used intact S49 mouse lymphoma cells to characteriz e the role of G proteins in the effect of barbiturates on cAMP regulat ion. cAMP accumulation was determined in intact S49 WT (wild-type) and S49 cyc(-) cells (the G(s alpha)-deficient mutant) by measuring the c onversion of [H-3]- ATP to [H-3]cAMP in cells preloaded with [H-3]aden ine. Pentobarbital enhanced cAMP accumulation in WT cells in the absen ce (basal) or presence of isoproterenol but had no effect on the EC(50 ) for isoproterenol. This effect was dose dependent with a 50-60% enha ncement at 2 mM pentobarbital. Pentobarbital did not affect forskolin- stimulated cAMP accumulation in WT cells. In cyc(-) cells, basal and f orskolin-stimulated cAMP accumulation were stimulated only at the high est concentration of pentobarbital used (2 mM). Pentobarbital did not affect the inhibition of cAMP accumulation by somatostatin in WT cells , and pertussis toxin treatment of WT cells did not affect the action of pentobarbital on cAMP accumulation. Pentobarbital did not affect is oproterenol-stimulated adenylyl cyclase activity in whole-cell homogen ates or membranes prepared from WT cells, The S-(-)-isomer of pentobar bital enhanced isoproterenol-stimulated cAMP accumulation more than th e R-(+)-isomer. Phenobarbital and barbituric acid did not enhance isop roterenol-stimulated cAMP accumulation, whereas the anesthetic barbitu rates hexobarbital, pentobarbital, and thiopental all enhanced activit y. These results suggest that pentobarbital enhances cAMP accumulation in intact WT cells by a mechanism that is dependent on G(s alpha) but independent of G(i). The properties of barbiturates that are responsi ble for the enhancement of cAMP accumulation may be related to the pro perties that are responsible for producing sedation and anesthesia.