Evidence for the distinct nature of f2-isoprostane receptors from
those of thromboxane a2.
Fukunaga, Megumu, Takafumi Yura, Ryszard Grygorczyk, and Kamal F.
Badr.
Renal Division, Department of Medicine, Emory University and
Veterans Affairs Medical Center, Atlanta, Georgia, Department of
Pharmacology, Merck Frosst for Therapeutic Research., Pointe Claire
-Dorval, Quebec, Canada
APStracts 3:0220F, 1996.
In rat glomeruli and mesangial cells, the thromboxane A2 mimetic,
U46,619, but not 8-iso-prostaglandin F2[alpha], reduced glomerular
inulin space and increased inositol 1,4,5 trisphosphate production,
effects abolished by SQ29,548. In competitive binding studies using
3H-8-iso-prostaglandin F2[alpha] or 3H-SQ29,548, mesangial cells
displayed thromboxane A2 binding sites, but not ones for 8-iso
-prostaglandin F2[alpha]. In contrast, rat aortic smooth muscle cells
possessed specific binding sites for both thromboxane A2 and 8-iso
-prostaglandin F2[alpha] and displayed functional responses to both
agonists, such as time- and dose-dependent activation of mitogen
-activated protein kinases. In these cells, the mean Kd value for the
isoprostane receptor was 31.8 +/- 5.7 nM. When human thromboxane A2
receptor cDNA was expressed in Xenopus oocytes injected with the
Ca++-specific photoprotein, aequorin, 8-iso-prostaglandin F2[alpha]
gave much weaker responses than U46,619. These studies provide the
first radioligand binding characteristics of the F2-isoprostane
receptor and demonstrate its specific and heterologous cellular
localization. They support the distinct nature and biological
significance of isoprostane receptors and provide a tool for their
further molecular characterization.
Received 15 July 1996; accepted in final form 19 November 1996.
APS Manuscript Number F198-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996