Ductus arteriosus responses to prostaglandin E1 at high and low oxygen concentrations

It previously has been suggested that prostaglandin E1 (PGE1) relaxes the ductus arteriosus in a low but not in an elevated oxygen environment. However, in the experiments reported here PGE1 relaxed rings on fetal lamb ductus arteriosus in vitro at both low (14 to 20 torr) and high (680 to 720 torr) oxygen tensions. The threshold concentration for PGE1 was 10(-10) M in either PO2 and the ED50's of PGE1 relaxation in high and low oxygen were 8.5 +/- 3.4 x 10(-10) M and 5.5 +/- 0.7 x 10(-10) M respectively. The magnitude of the relaxation was greater for the oxygen contracted ductus arteriosus than for that exposed to low oxygen. It is suggested that earlier reports of the lack of response of the ductus arteriosus to PGE1 in a high oxygen environment following relaxation in a low oxygen environment may be related to loss of response of the ductus arteriosus to repeated doses of PGE1 rather than to differences in PO2. Prostaglandin E1 therefore may play a significant role in the regulation of ductus arteriosus tone in the elevated oxygen environment of the newborn as well as the low oxygen environment of the fetus.