EFFECTS OF ENDOTHELIN-1 ON [CA2+](I) AND PH(I) IN TRABECULAR MESHWORKCELLS

We examined the effects of endothelin-1 (ET-1) on [Ca2+](i) and intrac ellular pH in cultured bovine trabecular meshwork cells and compared t he effects of ET-1 with those of angiotensin II (another phospholipase C activating peptide). [Ca2+](i) was measured with the Ca2+ fluoresce nt dye indo-1. Intracellular pH was measured using the pH sensitive fl uorescent dye BCECF. Exposure to ET-1 (10 nM) produced a transient inc rease in [Ca2+](i) (from 77.3 +/- 17.3 nM to 503.0 +/- 64.8 nM, p < 0. 05, n = 12). Intracellular pH was also increased during exposure to 10 nM ET-1 (+0.081 unit, p < 0.05, n = 6). In the presence of 10 mu M EI PA, ET-1 (10 nM) did not change intracellular pH. Angiotensin II did n ot significantly change [Ca2+](i) or intracellular pH. These results s uggest that ET-1 may be involved in the regulation of aqueous humor dy namics by changing [Ca2+](i) and intracellular pH in trabecular meshwo rk cells.