Expression of estrogen receptors alpha and beta in the corpus luteum and uterus from non-pregnant and pregnant llamas

Because estrogen may be involved in maternal recognition of pregnancy and embryonic migration in llamas, expression of estrogen receptor subtypes alpha (ERalpha) and beta (ERbeta) was evaluated in corpus luteum (CL), endometrium, and uterus using relative RT-PCR. Tissues were recovered from sterile-mated (SM) and pregnant (PG) females during Days 7-11 and 7-13 (Day 0 = day of mating), respectively, and follicular phase and juvenile females. Luteal expression of ERalpha and beta was similar (P > 0.10) in SM and PG females and within Days 7-11, however, expression of ERalpha in ovarian tissue from follicular phase females was greater (P < 0.05) than Days 7 and 9 CL. Uterus expressed less ERalpha and beta compared to endometrium (P = 0.07 and P < 0.01, respectively). Expression of ERalpha was greater (P < 0.05) in Day 7 and follicular phase uteri than Days 9 and 11, Day 13 PG and juvenile uteri. Uterine ERbeta expression was greater (P = 0.09) in PG versus SM females and in mated compared to follicular phase females (P < 0.05). Endometrial expression of ERalpha and beta did not differ (P > 0.10) between SM and PG females or by day. The presence of luteal ER during this period may mean a role for estradiol in maternal recognition of pregnancy. Observed increases in uterine ER expression with no changes in endometrium suggest expression increased in myometrium and/or perimetrium. Upregulation of myometrial ERbeta in PG females may be involved in supporting uterine migration of the embryo.