N6,O2'-Dibutyryl cyclic AMP and cholera toxin-induced beta-adrenergic receptor loss in cultured cells.

Saturation analysis of &adrenergic receptor binding sites was performed in intact C6-2B rat astrocytoma and HC-1 rat hepatoma cultured cells using the antagonist radioligand, (-)-[12sI]iodopindolo1.Incubation of C6-2B cells with W,b'-dibutyryl cyclic AMP and the phosphodiesterase inhibitor, 3-isobutyl-1-methylaranthine for 18 h caused a 31% reduction of B-receptor binding sites.Treatment of C6-2B cells with cholera toxin also induced a loss of cellular /3-receptor binding sites.An 118, 318, and 41% loss of 8-receptors was seen after a 4-, 12-, and 24-h incubation with 6 n~ cholera toxin.Receptor loss increased to 63% by treating C6-2B cells for 24 h with cholera toxin and 3-isobutyl-1-methylxanthine.The affinity of the remaining receptors for ( -)-['261]iodopindolo1 or isoproterenol was unaltered after 4-or 12-h cholera toxin treatment.Receptor loss occurred at times after the full development of cholera toxin-induced refractoriness to isoproterenol-stimulated cyclic AMP accumulation.HC-1 cells, which have &adrenergic receptor binding sites and the guanine nucleotide regulatory protein which is ADP-ribosylated by cholera toxin, but lack hormoneresponsive adenylate cyclase activity, did not lose sreceptors after a 24-h incubation with cholera toxin.There was, however, a 54% reduction of cellular /3receptors after the cells had been treated for 24 h with dibutyryl cyclic AMP in the presence of 3-isobutyl-l-