Regulation of prostanoid vasomotor effects and receptors in
choroidal vessels of newborn pigs.
Abran, Daniel, Daya R. Varma, and Sylvain Chemtob.
Centre de Recherche de l'H[circumflex]opital Sainte-Justine,
Department of Pediatrics and Department of Pharmacology, 3175
C[circumflex]ote Sainte-Catherine, Montr[acute]eal, Qu[acute]ebec,
H3T 1C5; and Department of Pharmacology and Therapeutics, McGill
University, Montr[acute]eal, Qu[acute]ebec, Canada H3G 1Y6
APStracts 3:0419R, 1996.
This study was conducted to determine if high perinatal prostaglandin
(PG) and thromboxane (TXA2) levels modified their choroidal vasomotor
effects and receptor levels. Both non-perfused (eye-cup 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
PGF2[alpha], TXA2, PGI2 and PGD2 levels were higher in the newborn
than in adult pigs; injections of ibuprofen (40 mg/kg/4 h for 48 h)
into newborn pigs significantly decreased choroidal levels of all
these prostanoids. PGF2[alpha] and the TXA2 mimetic U46619 caused
less choroidal vasoconstriction and production of inositol 1,4,5
-triphosphate (IP3) in the newborn than in adult pigs. Ibuprofen
treatment increased choroidal PGF2[alpha] vasoconstrictor effects,
IP3 production, and receptors, but did not modify response to U46619.
Carbaprostacyclin (PGI2 analog) caused a greater choroidal
vasodilatation and adenosine 3',5' cyclic monophosphate (cAMP)
production in the newborn than in adult pigs; these effects were not
modified by ibuprofen. PGD2 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,
Nw-nitro-L-arginine. These data suggest that high perinatal PG levels
downregulate PGF2[alpha] receptors and vascular effects but do not
modify choroidal responses to TXA2 and PGI2; NO seems to contribute
to the vasodilator effects of PGD2.
Received 6 May 1996; accepted in final form 30 October 1996.
APS Manuscript Number R253-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996