Dependence of intestinal arteriolar regulation on flow-mediated nitric oxide formation.
Our hypothesis was that a large fraction of resting nitric oxide (NO) formation is driven by flow-mediated mechanisms in the intestinal microvasculature of the rat. NO-sensitive microelectrodes measured the in vivo perivascular NO concentration ([NO]). Flow was increased by forcing the arterioles to perfuse additional nearby arterioles; flow was decreased by lowering the mucosal metabolic rate by reducing sodium absorption. Resting periarteriolar [NO] of large arterioles (first order; 1A) and intermediate-sized arterioles (second order; 2A) was 337 +/- 20 and 318 +/- 21 nM. The resting [NO] was higher than the dissociation constant for the NO-guanylate cyclase reaction of vascular smooth muscle; therefore, resting [NO] should be a potent dilatory signal at rest. Over flow velocity and shear rate ranges of approximately 40-180% of control, periarteriolar [NO] changed 5-8% for each 10% change in flow velocity and shear rate. The relationship of [NO] to flow velocity and shear rate demonstrated that 60-80% of resting [NO] depended on flow-mediated mechanisms. Therefore, moment-to-moment regulation of [NO] at rest is an ongoing process that is highly dependent on flow-dependent mechanisms.
Bohlen
H G
HG
Department of Physiology and Biophysics, Indiana University Medical School, Indianapolis, Indiana 46202, USA. gbohlen@iupui.edu
Nase
G P
GP
D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism*; D001783:Blood Flow Velocity / Q000187:drug effects; D003097:Collateral Circulation / Q000187:drug effects / Q000502:physiology; D007421:Intestine, Small / Q000098:blood supply* / Q000378:metabolism*; D008297:Male; D008833:Microcirculation / Q000187:drug effects / Q000378:metabolism; D008839:Microelectrodes; D009569:Nitric Oxide / Q000096:biosynthesis*; D010100:Oxygen / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D013314:Stress, Mechanical; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D009569:Nitric Oxide; D010100:Oxygen