Responses to the vasoconstrictor agents in the portal vein from SHRSP, especially in relation to aging.

Abstract

Abnormal responses to vasoconstrictor agents have been reported in the large vessels of SHRSP, but the large vessel may not functionally resemble a resistance vessel. Thus, it is unclear whether the abnormal responses observed in the large vessel are due to heredity or secondary effects due to blood pressure. We investigated the contractions by agonists in the portal vein which is not exposed directly to high blood pressure and may be analogous to a resistance vessel. The isolated portal veins from SHRSP and WKY at 1.5, 3, 6 and 12 months (M) were hung in the Magnus’ instrument containing Locke solution, and the change of tonus was recorded isometrically. The contractions by K+ and Ca++ increased with aging in SHRSP and WKY. The increase was larger in SHRSP than in WKY. The contraction at 1.5 M was not different between SHRSP and WKY, but there were remarkable differences at 3, 6 and 12 M. The contractions by noradrenaline, Ba, angiotensin II and prostaglandin F2α increased with aging in SHRSP, but the increase was not found in WKY. The contractions by these agonists at 1.5 M were not different between SHRSP and WKY; but there were remarable differences at 3, 6 and 12 M. The contraction by ACh was not changed by aging in SHRSP and WKY.