Independent regulation of periarteriolar and perivenular nitric oxide mechanisms in the in vivo hamster cheek pouch microvasculature.

Objective: We tested the hypothesis that differential stimulation of nitric oxide (NO) production can be induced in pre- and postcapillary segments of the microcirculation in the hamster cheek pouch.

Materials And Methods: We applied acetylcholine (ACh) or platelet-activating factor (PAF) topically and measured perivascular NO concentration ([NO]) with NO-sensitive microelectrodes in arterioles and venules of the hamster cheek pouch. We also measured NO in cultured coronary endothelial cells (CVEC) after ACh or PAF.

Results: ACh increased periarteriolar [NO] significantly in a dose-dependent manner. ACh at 1 microM increased [NO] from 438.1+/-43.4 nM at baseline to 647.9+/-66.3 nM, while 10 microM of ACh increased [NO] from baseline to 1,035.0+/-59.2 nM (P<0.05). Neither 1 nor 10 microM of ACh changed perivenular [NO] in the hamster cheek pouch. PAF, at 100 nM, increased perivenular [NO] from 326.6+/-50.8 to 622.8+/-41.5 nM. Importantly, 100 nM of PAF did not increase periarteriolar [NO]. PAF increased [NO] from 3.6+/-2.1 to 455.5+/-19.9 in CVEC, while ACh had no effect.

Conclusions: We conclude that NO production can be stimulated in a differential manner in pre- and postcapillary segments in the hamster cheek pouch. ACh selectively stimulates the production of NO only in arterioles, while PAF stimulates the production of NO only in venules.