Oestrogen receptors in endometrial cytosol of gilts on days 10-13 of oestrous cycle and pregnancy.

Cytosolic oestrogen receptors (ER(c)) were determined with a Dextran-coated charcoal assay and Scatchard plot analysis in endometrial tissue of non-pregnant and pregnant gilts on Days 10-13 after standing oestrus. The Kd of the ER(c) was 0.40 +/- 0.04 nM (mean +/- SEM) and was not affected by day or reproductive state. The endometrial ER(c) concentration was affected by day and reproductive state (P<0.001). During pregnancy, the endometrial ER(c) concentration declined from Day 10 (48.1 +/- 14.1 fmol/mg cytosol protein) to 13 (9.7 +/- 2.0 fmol mg-1 cytosol protein), but did not change in non-pregnant gilts. On Day 12 of pregnancy, the endometrial ER(c) concentration was significantly greater (P<0.01) in gilts with spherical blastocysts (30.2 +/- 5.4 fmol mg-1 cytosol protein) than in those gilts with filamentous blastocysts (9.8 +/- 2.6 fmol mg-1 cytosol protein).