Histamine and bradykinin stimulate the phosphoinositide turnover in human umbilical vein endothelial cells via different G-proteins.

The G-proteins which regulate hormonal turnover of phosphoinositide (PI) in human umbilical vein endothelial cells have been investigated. A 40-41 kDa doublet present in the membranes of these cells was selectively ADP ribosylated by pertussis toxin (PTx), and this doublet was Gi alpha 2 and Gi alpha 3 according to immunoblotting with specific antisera. By contrast, a doublet of 24-26 kDa proteins in the same membrane preparations was ADP ribosylated by the C3 component of botulinum toxin (BoTx). PTx-dependent ADP ribosylation blocked stimulation of PI turnover by histamine, but did not affect stimulation by bradykinin, whereas BoTx (C2 + C3 components) had the opposite effect. Thus two different groups of G-proteins may be involved in hormone-dependent stimulation of PI turnover in human umbilical vein endothelial cells.