Fig. 2.
Flow-induced nitric oxide (NO) production in coronary arterioles as measured by 4-amino-5-methylamino-2′2′-difluorofluorescein diacetate (DAF) fluorescence. A: representative images of vessels from young and old intact, OVX, and OVE rats at maximal flow (50 nl/s). B: DAF fluorescence increased in coronary arterioles from all groups at 50 nl/s flow (n = 6–11 mice/group). NO production in response to flow declined with age in intact females, as evidenced by reduced DAF intensity. OVX reduced NO production in vessels from young females. Estrogen replacement enhanced NO availability in vessels from old rats (A and B). C: treatment with the nitric oxide synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (l-NAME) inhibited flow-induced NO production in all groups (n = 3/group). Data are presented as means ± SE. *P < 0.05 vs. young intact. ‡P < 0.05 vs. age-matched OVX.