G. Fiol et al., ROLE OF NITRIC-OXIDE ON THE CENTRAL HEMODYNAMIC-RESPONSE TO ACUTE VOLUME EXPANSION IN THE PREGNANT RAT, American journal of obstetrics and gynecology, 178(4), 1998, pp. 823-829
OBJECTIVES: Our hypothesis was that during pregnancy nitric oxide acts
as mediator in the hemodynamic response to volume expansion. STUDY DE
SIGN: The study was performed on 12 rats on days 19 to 20 of pregnancy
. Six rats were injected intravenously with hexamethonium bromide plus
the inhibitor of nitric oxide synthase L-nitro-arginine methyl eater.
For a control group, six rats were injected with hexamethonium bromid
e plus the L-nitro-arginine methyl ester vehicle. A Volume expansion (
1.2% body weight) was performed in both groups by intravenous infusion
of bovine albumin (6%) solution. RESULTS: In the control group volume
expansion induced a hyperdynamic circulation characterized by increas
ed cardiac output, decreased total vascular resistance, and no change
in arterial pressure; however, in the study group volume expansion ind
uced a presser response without hyperdynamic circulation. CONCLUSION:
During pregnancy volume expansion induces a hyperdynamic circulatory s
tate possibly mediated by nitric oxide release. A defect in the releas
e of nitric oxide may be responsible for an inadequate hemodynamic res
ponse to volume expansion.