Effects of arachidonic acid, prostaglandin F2 alpha, prostaglandin E2, and arginine vasotocin on induction of birth in vivo and in vitro in a viviparous lizard (Sceloporus jarrovi).

The ability of arachidonic acid (AA) and prostaglandins of the two series to induce parturition in vivo and oviducal contraction in vitro was studied in the viviparous lizard Sceloporus jarrovi. Injection of PGF2 alpha, PGE2, or AA during late pregnancy stimulated parturition within 2 hr in a threshold-dependent fashion. In contrast, during mid pregnancy, females did not respond. Surgically removed and cultured oviducts from females in late pregnancy gave "birth" in response to AA, PGF2 alpha, and PGE2. Oviducts from S. jarrovi in mid pregnancy responded to PGF2 alpha but not to AA. Addition of arginine vasotocin, a potent stimulator of PG synthesis, either alone or with AA to oviduct cultures stimulated rapid and complete birth in vitro from oviducts obtained from late, but not mid pregnant, females. Stage of pregnancy mediates the response of the lizard oviduct to prostaglandin stimulation.