Hormonal Role of Adenosine In Maintaining Patency of the Ductus Arteriosus in Fetal Lambs

Publisher Website
Google Scholar
Abstract
The hypothesis that endogenously released adenosine plays an important role in maintaining patency of the fetal lamb ductus arteriosus was tested. The design of the study was to determine the effect, if any, of exogenous adenosine on blood flow through the ductus arteriosus and evaluate the relationship among the partial pressure of O2 in arterial blood, circulating endogenous plasma adenosine concentration, and the rate of blood flow through the ductus. When exogenous adenosine (5 .mu.moles) was administered during O2-induced ductal constriction, ductal blood flow increased from 101 .+-. 6 ml/min to 153 .+-. 4 ml/min (P < 0.01). When fetal blood adenosine concentrations were measured during nonventilation and ventilation with 100% O2, endogenous adenosine concentrations fell to < 1/2 of the preventilation levels, i.e., from 1.12 .+-. 0.17 to 0.49 .+-. 0.03 .mu.M (P < 0.01). Finally, when fetal lambs were ventilated with increasing concentrations of O2 (0%, 10%, 20%, 60%, and 100%) and measurements obtained simultaneously at each level, there was a significant monoexponential relationship among the rise in PO2, the fall in plasma adenosine concentration, and the decrease in ductal blood flow. These data suggest that: adenosine is a potent vasodilator of the lamb ductus arteriosus during O2-induced vasoconstriction; fetal endogenous plasma adenosine levels fall significantly when PO2 is increased; and the fall in adenosine concentrations parallels a decrease in ductal blood flow. The findings suggest that the endogenous vasodilator adenosine plays an important role in maintaining ductal patency in utero.