Defective formation of inositol 1,4,5-trisphosphate in bradykinin-stimulated fibroblasts from progressive systemic sclerotic patients.

The effect of bradykinin on inositol 1,4,5-trisphosphate (1,4,5-IP3) formation was investigated in fibroblasts from normal subjects and patients with progressive systemic sclerosis (PSS). 1,4,5-IP3 in both PSS and normal fibroblasts reached peak levels at 15 sec after stimulation with bradykinin, though this level was significantly lower in PSS fibroblasts than in normal cells. There was no difference in 1,4,5-IP3 content between islet-activating protein (IAP)-treated and untreated cells in either PSS or normal fibroblasts. These findings suggest that bradykinin stimulates phosphoinositide hydrolysis by phospholipase C in human fibroblasts via IAP-insensitive pathway, and that PSS fibroblasts appear to be defective in the pathway.