DOWN-REGULATION OF PROSTAGLANDIN-F2-ALPHA RECEPTORS IN RAT-LIVER DURING CHRONIC ENDOTOXEMIA

Prostaglandin (PG) F2-alpha binding parameters were measured in purified plasma membrane preparations isolated from livers of chronically endotoxin-(ET) treated rats and corresponding controls. Two classes of binding sites were detected in both groups: high affinity, low capacity, with a K(D) of 44.4 +/- 8.8 nM for saline- and 28.6 +/- 11.3 nM for ET-treated rats (n = 5 for both, p > 0.05) and low affinity, high capacity with a K(D) of 1.12 +/- 0.49-mu-M for saline- and 1.24 +/- 0.43-mu-M for ET-treated rats (p > 0.05). B(max) values for high affinity sites were 1.01 +/- 0.18 fmol.mg-1 protein for saline- and 1.02 +/- 0.54 (same units) for ET-treated rats (p > 0.05). There was a significant difference (p < 0.01) between the B(max) values for low affinity sites in saline- (675 +/- 332 fmol.mg-1 protein) and ET-treated rats (12 +/- 1, same units). This decrease in the amount of PGF2-alpha low affinity high capacity binding sites may underlie the depression of the PGF2-alpha stimulatory effect on hepatic gluconeogenesis induced by non-lethal, chronic ET treatment of rats, recently described by us (9).