Role of Increased Serine1176 Phosphorylation in Maintaining Normal Endothelial Responses in Male and Female Heterozygous Endothelial Nitric Oxide Synthase (NOS)‐Deficient Mice

Although endothelial responses in male and female heterozygous endothelial nitric oxide synthase (eNOS)‐deficient mice are normal, it is not known whether there is compensation for the loss of a single eNOS gene by vasodilator mechanisms other than NOS and nitric oxide. The goal of the present study was to test the hypothesis that endothelial responses in male and female heterozygous endothelial nitric oxide (eNOS)‐deficiency are due to NOS‐dependent signaling pathways. Responses of carotid arteries from male and female eNOS+/+ and eNOS+/‐ mice to acetylcholine (Ach) and nitroprusside (NP) were examined in the presence of vehicle (saline), L‐NNA (100 µM; a NOS inhibitor), or ODQ (1 µM; an inhibitor of soluble guanylyl cyclase, sGC). Responses to Ach and NP were similar in male and female eNOS+/+ and eNOS+/‐ mice treated with vehicle. Carotid artery responses to Ach were significantly inhibited in male and female eNOS+/+ mice in the presence of L‐NNA and ODQ. For example, acetylcholine produced 89±2, 21±8 and 3±5% relaxation in vehicle, L‐NNA, and ODQ treated vessels from male eNOS+/+ mice. L‐NNA and ODQ produced a similar degree of inhibition of Ach‐induced relaxation in male and female eNOS+/‐ mice. Although vascular eNOS expression was reduced by 蠅60%, phosphorylation at Ser1176 (a site associated with increased eNOS activity) was markedly higher in eNOS+/‐ mice. These findings demonstrate that endothelial responses in male and female eNOS+/‐ mice maintain their dependency on NOS and sGC. Increased eNOS phosphorylation appears to be a compensatory mechanism that serves to maintain endothelial responses in the absence of a single eNOS gene. Supported by NIH HL‐089884 and HL‐107632.