Increased receptor-mediated phospholipase D activation and Ca2+ mobilization in peritoneal polymorphonuclear...

Phospholipase D activation was investigated in peritoneal polymorphonuclear leukocytes from streptozotocin-induced diabetic rats. Stimulation of the cells with formyl-Met-Leu-Phe resulted in a time- and dose-dependent increase in phosphatidylethanol in the presence of ethanol, and this lipid formation in cells prepared from diabetic rats was enhanced as compared to that in the case of nondiabetic rats. Furthermore, the increase in the intracellular Ca2+ concentration was also enhanced in the stimulated cells from diabetic rats. Under the present conditions, N-acetyl-beta-glucosaminidase release and superoxide generation, which are known to be dependent on phospholipase D activation, were higher in the cells from diabetic rats than those in the cells from control rats. However, there was no difference in the dissociation constant and the number of binding sites for formyl-Met-Leu-Phe between the cells from diabetic and control rats. Phosphatidylethanol formation, N-acetyl-beta-glucosaminidase release and superoxide generation in response to ionomycin or 4 beta-phorbol 12-myristate 13-acetate were not enhanced in diabetic rat cells, as compared with those in control rat cells. These results suggest that receptor-mediated phospholipase D activation and Ca2+ mobilization are enhanced in diabetic rat polymorphonuclear leukocytes, which might be due to acceleration of receptor-mediated signaling.