Acceleration of oviductal transport of oocytes induced by estradiol in cycling rats is mediated by nongenomic stimulation of protein phosphorylation in the oviduct

In order to explore nongenomic actions of estradiol (E,) and progesterone ( P-4) in the oviduct, we determined the effect of E-2 and P-4 on oviductal p rotein phosphorylation. Rats on Day 1 of the cycle (C1) or pregnancy (P1) w ere treated with E-2, P-4, or E-2 + P-4, and 0.5 h or 2.5 h later their ovi ducts were incubated in medium with P-32-orthophosphate for 2 h. Oviducts w ere homogenized and proteins were separated by SDS-PAGE. Following autoradi ography, protein bands were quantitated by densitometry. The phosphorylatio n of some proteins was increased by hormonal treatments, exhibiting steroid specificity and different individual time courses. Possible mediation of t he E-2 effect by mRNA synthesis or protein kinases A (PK-A) or C (PK-C) was then examined. Rats on C1 treated with E-2 also received an intrabursal (i .b.) injection of alpha -amanitin (Am), or the PK inhibitors H-89 or GF 109 203X, and 0.5 h later their oviducts were incubated as above plus the corre sponding inhibitors in the medium. increased incorporation of P-32 into tot al oviductal protein induced by E-2 was unchanged by Am, whereas it was com pletely suppressed by PK inhibitors. Local administration of H-89 was utili zed to determine whether or not E-2-induced egg transport acceleration requ ires protein phosphorylation. Rats on C1 or P1 were treated with E-2 s.c. a nd H-89 Lb. The number and distribution of eggs in the genital tract assess ed 24 h later showed that H-89 blocked the E-2-induced oviductal egg loss i n cyclic rats and had no effect in mated rats. It is concluded that E-2 and P-4 change the pattern of oviductal protein phosphorylation. Estradiol inc reases oviductal protein phosphorylation in cyclic rats due to a nongenomic action mediated by PK-A and PK-C. In the abscence of mating, this action i s essential for its oviductal transport accelerating effect. Mating changes the mechanism of action of E-2 in the oviduct by waiving this nongenomic a ction as a requirement for E-2-induced embryo transport acceleration.