This study was designed to establish (a) whether prostaglandin E2 (PGE2) can reach the ovary and oviduct by a local pathway and what is the contribution of lymphatic vessels to this transfer, and (b) whether PGE2 can permeate from venous and lymphatic vessels of the mesometrium to arterial blood and be delivered to the uterine horn during maternal recognition of pregnancy in gilts. The reproductive tract was excised from gilts (n = 10) on day 14 after mating. The uterine horn was isolated with the ovary and broad ligament and perfused with warmed and oxygenated autologous blood. A total dose of 5.5 x 10(7) disintegrations per min (d.p.m.) (49 ng) [3H]PGE2 was infused into the small branches of the uterine vein on the broad ligament or into the lymphatic vessels. Frequent blood samples were collected from the branch of the uterine artery and from the venous effluent. Tissue samples were collected from the uterine horn, the ovary and the broad ligament. The concentration of [3H]PGE2 was significantly higher in the ovary (P < 0.001), oviduct (P < 0.01), endometrium (P < 0.01), myometrium (P < 0.001) and mesometrium (P < 0.001) after infusion of [3H]PGE2 into lymphatic vessels than into the branches of the uterine vein. In contrast, the concentration of [3H]PGE2 was significantly higher in arterial blood supplying the uterine horn (P < 0.01) and in the venous effluent (P < 0.001) after infusion of [3H]PGE2 into the branches of the uterine vein than into lymphatic vessels. These results demonstrated local transfer of [3H]PGE2 into the ovary, oviduct and uterine horn from lymphatic and venous vessels of the mesometrium. However, the efficiency of this transfer was considerably higher after infusion into lymphatic vessels than into branches of the ovarian vein. We conclude that the lymphatic pathway is a fundamental mechanism in the local transfer of PGE2 from the uterus to the ovary and oviduct during early pregnancy in the pig.