Differential patterns in luteal prolactin and LH receptors during pregnancy in sows and ewes

In the sow, a dramatic increase of LH specific binding was observed during the second half of pregnancy. This was due to an increase in receptor number (41 fmol and 95 fmol/mg protein at Days 50 and 105 respectively). The apparent association constant was unchanged. The pattern of prolactin receptor content showed two peaks at Day 60 and Day 105. Prolactin receptors increased earlier during pregnancy than did LH receptors, suggesting a possible role of prolactin in the induction of LH receptors. In the ewe, the receptor content of LH and prolactin did not change very much during pregnancy. The corpus luteum showed normal luteal function until parturition although it was not necessary for maintenance of pregnancy in the ewes.