Fig. 4.

Activation of COX-1 by NO. Sodium nitroprusside increase COX-1 activity in sheep seminal vesicles, as evidenced by a dose-dependent increase in PGE₂ release from arachidonic acid; hemoglobin (Hb) attenuates the effects of sodium nitroprusside (SNP) consistent with an NO-mediated activation of COX-1. Results are expressed as the means ± SE of seven experiments and analyzed by Student's unpaired t-test. *P < 0.01 compared with results obtained in the absence of SNP and †P < 0.01 compared with results obtained in the presence of SNP but absence of Hb. Experimental design is detailed in Refs. 127 and 128.