Regulation of prostanoid vasomotor effects and receptors in choroidal vessels of newborn pigs

This study was conducted to determine if high perinatal prostaglandin (PG) and thromboxane (TxA(2)) levels modified their choroidal vasomotor effects and receptor levels. Both nonperfused (eyecup preparations) and perfused choroidal vessels from saline- or ibuprofen-treated 1-day-old pigs and tissues from adult pigs were used; all prostanoids produced similar vasomotor effects on both preparations. Choroidal PGF(2 alpha), TxA(2), PGI(2), and PGD(2) levels were higher in the newborn than in adult pigs; injections of ibuprofen (40 mg/kg every 4 h for 48 h) into newborn pigs significantly decreased choroidal levels of all these prostanoids. PGF(2 alpha) and the TxA(2) mimetic U-46619 caused less choroidal vasoconstriction and production of inositol 1,4,5-trisphosphate (IP3) in the newborn than in adult pigs. Ibuprofen treatment increased choroidal PGF(2 alpha) vasoconstrictor effects, IP3 production, and receptors, but did not modify response to U-46619. Carbaprostacyclin (PGI(2) analog) caused a greater choroidal vasodilatation and adenosine adenosine 3',5'-cyclic monophosphate (cAMP) production in the newborn than in adult pigs; these effects were not modified by ibuprofen. PGD(2) did not increase cAMP but caused greater dilatation and nitrite [oxidation product of nitric oxide (NO)] production in the choroid of newborn than of adult pigs, which were decreased to adult levels by ibuprofen and the NO synthase inhibitor N-omega-nitro-L-arginine. These data suggest that high perinatal PG levels downregulate PGF(2 alpha), receptors and vascular effects but do not modify choroidal responses to TxA(2) and PGI(2); NO seems to contribute to the vasodilator effects of PGD(2).