Nitric oxide (NO) is an important hemodynamic mediator of sepsis; however, its visceral microcirculatory effects are largely unknown. To determine the role of systemic nitric oxide synthase (NO-S) inhibition on the microcirculation of the small intestine (SI), an intact loop of SI was exteriorized from decerebrate rats into a controlled tissue bath. Videomicroscopy was used to measure arteriolar diameters (A1, A3) and optical Doppler velocimetry was used to quantitate flow. In nonbacteremic controls inhibition of NO-S by N omega-nitro-L-arginine methyl ester (L-NAME; 1 mg/kg IV) caused vasoconstriction (A1 = -7%; A3 = -24% baseline values) and reduced A1 flow by 26%. Bacteremic controls received 10(9) Escherichia coli IV, which resulted in arteriolar constriction and hypoperfusion (A1 = -16%; A3 = -21%; A1 flow = -44%), despite increased cardiac output (+33%). Treatment of bacteremic rats with L-NAME corrected the increased cardiac output (-3%), but exacerbated vasoconstriction (A1 = -24%; A3 = -27%) and did not improve A1 flow (-49%). These data indicate that (1) NO mediates basal microvascular tone of the SI; (2) hyperdynamic bacteremia causes arteriolar constriction and hypoperfusion of the SI; and (3) although systemic NO-S inhibition normalizes cardiac output and increases blood pressure, it aggravates vasoconstriction in the SI and does not improve hypoperfusion.
View details for Web of Science ID A1994NN28300022
View details for PubMedID 7514673