Genital sensory stimulation shifts estradiol intraoviductal signaling from nongenomic to genomic pathways, independently from prolactin surges
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Date
2007
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SOC BIOLGIA CHILE
Abstract
Estradiol (132) accelerates oviductal egg transport through nongenomic pathways involving oviductal protein phosphorylation in non-mated rats, and through genomic pathways in mated rats. Here we investigated the ability of cervico-vaginal stimulation (CVS) to switch the mode of action of E 2 in the absence of other male-associated components. Pro-estrous rats were subjected to CVS with a glass rod and 12 hours later were injected subcutaneously with E 2 and intrabursally with the RNA synthesis inhibitor Actinomycin D or the protein phosphorylation inhibitor H-89. The number of eggs in the oviduct, assessed 24 It later, showed that Actinomycin D, but not H-89 blocked the E-2-induced egg transport acceleration. This clearly indicates that CVS alone, without other mating-associated signals, is able to shift E 2 signaling from nongenomic to genomic pathways. Since mating and CVS activate a neuroendocrine reflex that causes iterative prolactin (PRL) surges, the involvement of PRL pathway in this phenomenon was evaluated. Prolactin receptor mRNA and protein expression in the rat oviduct was demonstrated by RT-PCR and Western blot, but their levels were not different on day 2 of the cycle (C2) or pregnancy (P2). Activated STAT 5a/b (phosphorylated) was detected by Western blot on P2 in the ovary, but not in the oviduct, showing that mating does not stimulate this PRL signalling pathway in the oviduct. Other rats subjected to CVS in the evening of pro-estrus were treated with bromoergocriptine to suppress PRL surges. In these rats, H-89 did not block the E-2-induced acceleration of egg transport suggesting that PRL surges are not essential to shift E-2 signaling pathways in the oviduct. We conclude that CVS is one of the components of mating that shifts E-2 signaling in the oviduct from nongenomic to genomic pathways, and this effect is independent of PRL surges elicited by mating.
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Keywords
mating, oviduct, estradiol, signaling pathways, prolactin receptor, egg transport, rat, TYROSINE KINASE, RECEPTOR GENE, DEVELOPMENTAL EXPRESSION, CORPUS-LUTEUM, RAT, TRANSPORT, PROTEIN, PHOSPHORYLATION, CELLS, ACTIVATION