Steroid Concentrations in Uterine Lymph and Uterine Arterial Plasma of Guts During the Estrous Cycle and Early Pregnancy1

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Abstract
This study was conducted to determine if the lymphatic vessels which drain fluid from the uterus act in addition to uterine veins in transporting steroids from the early gravid uterus. Concentrations of estrone (E1), estradiol-17.beta. (E2.beta.) and progesterone (P4) were quantified in uterine arterial blood and uterine lymph, collected from gilts during the estrous cycle and early pregnancy. Twenty-four Yorkshire gilts were assigned randomly in equal numbers to be mated on the 1st day of behavioral estrus (day 0) or serve as nonmated controls. Mated and nonmated gilts were assigned to surgery on days 11 (4), 13 (4) or 15 (4) of the estrous cycle or pregnancy. Uterine arterial blood (10 ml) and uterine lymph (500 .mu.l) were collected from a branch of the middle uterine artery and an adjacent uterine lymphatic which was above the anastomosis of the ovarian and uterine lymphatic systems. Pregnancy was vertified in mated gilts by the presence of conceptuses in uterine flushings. In pregnant (P) and nonpregnant (NP) gilts, there was no effect of day on the concentrations of E1, E2.beta. or P4 in uterine arterial plasma or uterine lymph. Concentrations of E1 and E2.beta. were greater (P < 0.01) in uterine lymph collected from P gilts, when compared to NP gilts across all days sampled (35.5 .+-. 1.5 vs. 26.7 .+-. 1.6 and 34.0 .+-. 3.9 vs. 17.7 .+-. 2.1 pg/ml, respectively). In contrast, no differences in E1 or E2.beta. were found between uterine arterial plasma of P and NP gilts. Regardless of pregnancy status, uterine lymph contained greater (P < 0.01) concentrations of E1 and E2.beta. and less (P < 0.01) P4 than uterine arterial plasma (31.1 .+-. 1.4 vs. 11.5 .+-. 0.7 pg/ml, 25.9 .+-. 2.8 vs. 10.4 .+-. 0.7 pg/ml and 9.8 .+-. 1.2 vs. 39.8 .+-. 3.5 ng/ml, respectively). These data demonstrate a greater estrogen to P4 ratio in uterine lymph of P than NP gilts, providing direct evidence that the lymphatic vessels draining the gravid porcine uterus function in addition to the venous system for the transport of steroids.