Effects of vasoactive agents on isolated human umbilical arteries and veins.

ALTURA, BURTON M., D. MALAVIYA, CHARLES F. REICH, AND LOUIS R. ORKIN. Effects of vasoactive agents on isolated human umbilical arteries and veins. Am. J. Physiol. 222(Z): 345-355. 1972.In vitro experiments, using both helically and longitudinally cut human umbilical arteries and veins (HUAV), were designed to determine: I) whether any of the known circulating vasoactive substances can induce contraction of these vessels in low (physiologic?) concentrations; 2) the relative potency of these substances; 3) the existence of specific drug receptors which subserve contraction; and 4) the relative contribution each type of smooth muscle layer (i.e., longitudinal vs. circular) may play in response to vasoactive agents and in development of spontaneous mechanical activity. The results indicate : 1) 10 different vasoactive agents (amines, polypeptides, prostaglandins, and potassium ions) induce varying degrees of unequal contractile responses (serotonin = maximum); 2) only serotonin ( <O. 1 pg/liter), bradykinin (0.5-4 pg/liter), and oxytocin (l-5 mU /liter) induce contractile responses in very low (physiologic?) concentrations; 3) specific drug receptors appear to exist for all 10 agents in HUAV; 4) dose-response curves for longitudinally cut strips do not always parallel those of the helically cut strips; and 5) circular smooth muscle appears to play a greater role than longitudinal smooth muscle in spontaneous mechanical activity of HUAV.