Effect of divergent selection for uterine capacity on progesterone, estradiol and cholesterol levels around implantation time in rabbits.

Abstract:

The effects of selection for high (H) and low (L) uterine capacity on serum and uterine fluid levels of progesterone and serum levels of estradiol and cholesterol, near implantation (day 6 of gestation), were studied. Both lines had similar ovulation rates (15.2 vs 14.4), but different number of embryos (12.8 vs 11.0; P<0.05) for H and L, respectively. Progesterone, cholesterol and estradiol were similar in both lines (9.3 and 9.6 ng/ml serum progesterone; 15.6 and 13. 7 ng/ml of uterine fluid progesterone; 28.1 and 27.6 pg/ml of estradiol; and 66.6 and 68.0 mg/dl of cholesterol for H and L, respectively). Lactation strongly affected the variables studied. Lactating does had higher ovulation rates than non-lactating (15.6 vs 14.0; P<0.05), but no differences were detected for the number of embryos recovered (12.2 and 11.6 for lactating and non-lactating, respectively) or for embryo survival (0. 79 and 0.84 for lactating and non-lactating). L does had lower levels of serum progesterone (8.7 ng/ml), uterine fluid progesterone (13.0 ng/ml) and serum cholesterol (59.3 mg/dl) than non-lactating females (10.2 ng/ml, 16.3 ng/ml and 75.3 mg/dl respectively; P<0.05). Lactation did not affect serum levels of estradiol. Serum progesterone levels were slightly correlated with ovulation rate (r=0.24; P<0.05). Ovulation rate and number of embryos recovered were correlated with progesterone uterine fluid in lactating females (r=0.55 and 0.49 respectively; P<0.05). Embryo survival in lactating females was negatively correlated with the concentration of estradiol (r=-0.39; P<0.05).

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