Inhibition of the amplified bombesin-stimulated inositol phosphate response in N-ras transformed cells by high density culturing.

The bombesin-stimulated inositol phosphate response is only increased in cells transformed by the overexpression of N-ras when they are cultured under sub-confluent conditions. The inhibition of the amplified bombesin stimulation can be partially reversed by either, incubation of the cells for 5 h with 1 mM suramin, or by a 30 min preincubation of cells in excess buffer. The inhibitory effects are probably caused by the effects of autocrines and may explain some of the different published observations concerning the effects of ras gene products upon inositol phospholipid metabolism.