AJP - Gastrointestinal and Liver Physiology, Vol 252, Issue 2 158-G162, Copyright © 1987 by American Physiological Society
Vascular reactivity in experimental portal hypertension
A. Bomzon and L. M. Blendis
Portal hypertension (PHT) is known to be associated with a hyperdynamic
circulation, yet the pathogenesis of both remains unclear. Therefore, we
have studied serially the relationship between portal pressure and in vitro
peripheral vascular responsiveness in an animal model of presinusoidal PHT.
In rats with partial portal vein stenosis (PPVS) or sham-operated (SO)
controls, we studied contractile responses to cumulative doses of
norepinephrine (NE) and to a single dose of 0.8 microM NE of 20-mm
helically cut strips of thoracic aorta. At both 2 and 10 days
postoperatively, the portal pressures (mean intrasplenic pressure) in PPVS,
14.3 +/- 1.5 mmHg and 14.1 +/- 1.3 mmHg were significantly elevated
compared with SO controls, 7.6 +/- 0.6 mmHg (P less than 0.005) and 9.7 +/-
0.5 mmHg (P less than 0.01), respectively. Yet, there was no significant
differences between the two groups in the Rmax and ED50 of the contractile
response curves to cumulative doses of NE as well as in the fast (phase 1)
and slow phase (phase 2) of the contraction to 0.8 microM NE. In contrast,
at 21 days, portal pressure in the PPVS rats fell to 11.0 +/- 0.7 mmHg but
remained significantly higher than that of the SO controls, 8.2 +/- 1.0
mmHg (P less than 0.05). This occurred in conjunction with a significant
decrease in Rmax [698 +/- 87 mg (PPVS) vs. 1148 +/- 92 mg (SO); P less than
0.005] but no significant change in ED50, indicating a decreased
sensitivity to NE due to an alteration in alpha-adrenoreceptor
function.(ABSTRACT TRUNCATED AT 250 WORDS)
