Detection of functional oxytocin receptors on endometrium of pigs

Oxytocin (OT) stimulates phosphoinositide (PI) hydrolysis and prostaglandin (PG) F2 alpha secretion from the endometrium of cyclic pigs, but the presence of specific endometrial receptors for OT has not been demonstrated in this species. Two experiments were performed to detect the presence of functional OT receptors on endometrium collected 15 days post estrus from cyclic gilts. OT receptor density and Kd were determined by receptor assay and Scatchard analysis. Hydrolysis of PI (i.e., incorporation of [3H]inositol into total inositol phosphates) and PGF2 alpha secretion were studied with use of incubations of endometrial explants. Concentrations of PGF2 alpha were log-transformed for analysis of variance and are expressed as means +/- standard error of log-transformed data. In experiment 1, mean density and mean Kd of OT receptors on endometrium of gilts were 29.2 +/- 5.54 fmol/mg protein and 1.59 +/- 0.23 nM, respectively. OT receptor density was significantly correlated with the ability of 100 nM OT to stimulate PI hydrolysis (r = 0.83, p < 0.05) and PGF2 alpha secretion (r = 0.87, p < 0.10), but was not highly correlated with receptor Kd (r = -0.08, p = 0.85). In contrast, OT receptor Kd was not highly correlated with OT-stimulated PI hydrolysis (r = -0.19, p = 0.68) or OT-stimulated PGF2 alpha secretion (r = 0.14, p = 0.86). OT-stimulated PI hydrolysis was also significantly correlated (r = 0.80, p < 0.05) with OT-stimulated PGF2 alpha secretion.(ABSTRACT TRUNCATED AT 250 WORDS)