Meclofenamate and prostaglandin E2 affect breathing movements independently of glucose concentrations in fetal sheep

Abstract

Fetal breathing movements in sheep are stimulated by infusions of a prostaglandin synthetase inhibitor, meclofenamate; they are inhibited by prostaglandin E2. Recent studies suggest that these effects are mediated through changes in fetal plasma glucose concentrations. We infused into chronic fetal sheep preparations (1) glucose, (2) meclofenamate, and (3) prostaglandin E2, followed by prostaglandin E2 and glucose together. Infusions of glucose alone did not affect fetal breathing movements despite a significant twofold increase in glucose concentrations. During meclofenamate infusions, fetal breathing movements increased from 34.9% to 80.6% (p < 0.005); glucose concentrations did not change. During prostaglandin E2 infusions, fetal breathing movements decreased from 36.5% to 4.1% (p < 0.005) without any change in glucose concentrations; the addition of glucose did not alter the effects of prostaglandin E2 on fetal breathing movements. We conclude that fetal infusions of glucose in sheep do not affect fetal breathing movements and the effects on these breathing movements produced by meclofenamate and prostaglandin E2 are independent of the changes in plasma glucose concentrations.