INTRAOVIDUCTAL ADMINISTRATION OF RIBONUCLEIC-ACID FROM ESTROGEN-TREATED RATS MIMICS THE EFFECT OF ESTROGEN ON OVUM TRANSPORT

In order to determine whether or not ovum transport acceleration induc ed by estradiol (E(2)) requires RNA and protein synthesis in the ovidu ct, inhibitors of RNA and protein synthesis were injected locally in r ats treated with E(2). We also tested whether administration of oviduc tal RNA from E(2)-treated rats could mimic the effect of E(2) on ovum transport. Rats on Day 2 of pregnancy were given a single s.c. injecti on of 10 mu g E(2) and an intraoviductal (i.o.) injection of actinomyc in D, alpha-amanitin, or cycloheximide (Chx). In control groups, eithe r the steroid or the inhibitor or both were replaced by the respective vehicle. RNA obtained from oviduct or ileum of E(2)-treated rats or f rom the oviduct of propylene glycol-treated rats was injected into the oviducts of recipient rats on Day 1 of pregnancy. Animals were autops ied 24 h later to determine the number and distribution of eggs in the genital tract. All three inhibitors partially blocked the E(2)-induce d ovum transport acceleration, whereas administration of inhibitors al one did not affect oviductal egg recovery. Only oviductal RNA obtained from E(2)-treated rats decreased the number of oviductal eggs (active extract). To interpret this finding, the active extract was preincuba ted with RNase or DNase before i.o. administration, Other groups of re cipient rats also treated with active extract were injected s.c. with Chx, or their uterine horns were ligated to disclose the fate of the m issing oviductal eggs. Active extract treated with RNase did not decre ase the number of oviductal eggs; Chx blocked the effect of the active extract; and eggs missing from the oviduct were partially recovered i n the uteri of ligated recipient rats. It is concluded that protein sy nthesis in the oviduct is required for the full effect of E(2) on ovum transport and that one or more RNA species induced by E(2) in the ovi duct are by themselves able to mimic, and therefore mediate, the effec t of E(2) on ovum transport.