INOSITOL PHOSPHATE-DIACYLGLYCEROL SIGNALING PATHWAY IN REGULATION OF INTRAOCULAR-PRESSURE

To clarify the role of the inositol phosphate diacylglycerol (PI) sign aling pathway in the regulation of intraocular pressure (IOP), we exam ined the effects of the tumor promoter phorbol ester (PMA) and Ca iono phore A23187 on IOP responses in albino rabbits. It was known that PMA stimulates protein kinase C (PKC) directly and that A23187 elevates i ntracellular Ca2+ concentration. In this study, the topical applicatio n of 10 muM PMA or 15 muM A23187 slightly reduced IOP. However, when b oth 10 muM PMA and 15 muM A23187 were topically applied the IOP was si gnificantly reduced between 2 and 10 hours after A23187 application. T he maximum IOP decrease was 5.0 mmHg at 3 hours. This decrease was inh ibited by pretreatment with 0.5 muM staurosporin, a PKC inhibitor. The se findings suggest that the PI signaling pathway somehow mediates aqu eous dynamic changes in the eye.