The developmental response of the ductus arteriosus to oxygen.

We studied the isometric contractile effects of increased PO2 on isolated rings of lamb ductus arteriosus (from three different gestational age groups). When rings were stretched to initial lengths that result in a maximal contractile response for rings in that age group, the oxygen-induced contraction was 5.91 +/- 0.72 g/mm2 (+/-SEM, n = 18) in animals older than 135 days, 5.55 +/- 1.23 g/mm2 (n = 18) in animals between 111 and 130 days, and 3.85 +/- 0.75 g/mm2 (n = 19) in animals between 87 and 110 days. Only in the most immature vessels could a decrease in the tissue's response to oxygen be observed.