LONG TERM PROSTAGLANDIN SYNTHESIS INHIBITORS (PGSI) AND TRACHEAL FLUID (TF) PRODUCTION IN FETAL SHEEP

Abstract

In fetal sheep, TF production is relatively constant during the last month of gestation; it decreases in the few days before birth, a time when fetal plasma PGE2 concentrations ([PGE2]) are rising. Short term (12 h) infusions of PGE2 decrease TF production, suggesting that the rise in endogenous [PGE2] may be responsible for the prepartum decrease in TF production. To investigate the possible role of PGE2 in the control of TF production before birth, we studied 5 chronically catheterized fetal sheep from 131-150d gestation. In 4 animals, we infused meclofenamate (Mec), a PGSI, at 1.4-2.8 mg/h (a dose previously shown to decrease [PGE2]); the infusion was continued until birth or fetal demise (5-13d). A control animal received an infusion of vehicle only, for 11d. Each day we collected tracheal fluid from a tracheal cannula and a soft, intrauterine collection bag. TF production in experimental and control animals was similar to previously reported normal values. During the 2 days prior to birth TF production progressively decreased in all animals to 30% of the usual rate; this decrease is similar to that previously reported. Thus, Mec did not prevent the prepartum decrease in TF production. We conclude that in the last few days before birth, the rise in [PGE2] does not cause the fall in TF production. (Supported by USPHS Grant HL 27356 (Pulmonary SCOR) and ALA Fellowship Grant.)