Protein phosphorylation in intact coronary endothelial cells by bradykinin

Abstract

In cultured coronary endothelial cells obtained from guinea pig hearts, bradykinin (10 −6 M) stimulated the 32P i-incorporation into 5 substrate proteins with molecular weights corresponding to 27, 32, 60, 86 and 100 kDa. The time course of phosphorylation of the 60, 86 and 100 kDa proteins was rapid (within 30 s), but transient (max. within 1–2 min.), while the 32P i incorporation into the 27 and 32 kDa protein was delayed but increased within 10 minutes. Ca ++-ionophore A 23187 (10 −5 M) and 12-O-tetradecanoylphorbol-13-acetate (TPA) (10 −5 M) both mimicked the effects of the bradykinin induced phosphorylation pattern. While A 23187 enhanced the phosphorylation of the 27, 60 and 100 kDa substrates, TPA increased the 32P i-incorporation into the 32 and 86 kDa proteins. Furthermore the time course of protein phosphorulation elicited by A 23187 and TPA showed marked similiarities to those obtained with bradykinin. Our findings are consistent with the view, that stimulation of coronary endothelial bradykinin-receptors activates both Ca ++-dependent protein kinases and protein kinase C.