ANTENATAL GLUCOCORTICOID TREATMENT ATTENUATES IMMEDIATE POSTNATAL PROSTACYCLIN AND THROMBOXANE LEVELS IN PLASMA OF VERY PRETERM LAMBS

The effect of antenatal glucocorticoid treatment on the production of cyclooxygenase metabolites was studied in very preterm lambs. Seven fe tal lambs, 121 days of gestation, received a single dose of betamethas one, 0.5 mg/kg i.m., 48 h prior to delivery. Five age-matched controls received saline intramuscularly. Each fetus was delivered and ventila ted for 3 h and sacrificed. Plasma was prepared from blood drawn from the umbilical cord of each fetus, and 60, 120 and 180 min after delive ry. Mesenteric (MESA) and femoral (FEMA) arteries were isolated and in cubated in Krebs' buffer for 10 min at 37 degrees C. Samples were extr acted for prostacyclin (PGI(2)), and thromboxane (Tx)A(2), purified by HPLC and measured by specific radioimmunoassay. Amounts of metabolite s measured postnatally from betamethasone-treated preterm lambs were s ignificantly lower (p < 0.05) than the amounts from saline lambs. Pros tacyclin production by MESA and FEMA of betamethasone-treated lambs wa s lower than by vessels of saline-treated lambs. There was no differen ce in TxA(2) production by vessels from the two groups of preterm lamb s. Our data show that antenatal betamethasone treatment decreased syst emic prostanoid production suggesting a decreased reactivity of the va scular membrane.