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¹ Unidad de Reproducción y Desarrollo, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
² Millennium Institute for Fundamental and Applied Biology, Santiago, Chile

(Requests for offprints should be addressed to P A Orihuela; Email: porihuel{at}bio.puc.cl)

Oestradiol (E₂) accelerates oviductal transport of oocytes in cycling rats through a nongenomic pathway that involves the cAMP–PKA signalling cascade. Here we examined the role of the inositol triphosphate (IP3) and mitogen-activated protein kinase (MAPK) signalling cascades in this nongenomic pathway. Oestrous rats were injected with E₂ s.c. and intrabursally (i.b) with the selective inhibitors of phospholipase C (PLC) ET-18-OCH₃ or MAPK PD98059. The number of eggs in the oviduct assessed 24 h later showed that ET-18-OCH₃ blocked E₂-induced egg transport acceleration, whereas PD98059 had no effect. Other oestrous rats were treated with E₂ s.c. and 1, 3 or 6 h later oviducts were excised and the levels of IP3 and phosphorylated MAPK p44/42 (activated) were determined by radioreceptor assay and western blot, respectively. Oestradiol administration increased IP3 level at 1 and 6 h after treatment, whereas activated MAPK p44/42 level was unchanged. Finally, we explored whether cAMP-PKA and PLC-IP3 signalling cascades are coupled. Inhibition of adenylyl cyclase by i.b. injection of SQ 22536 blocked the increase of IP3 levels induced by E₂, while inhibition of PLC by ET-18-OCH₃ had no effect on E₂-induced PKA activity. Furthermore, activation of adenylyl cylase by Forskolin increased oviductal IP3 levels. Thus, activation of PLC-IP3 by E₂ requires previous stimulation of cAMP-PKA. We conclude that the nongenomic pathway utilised by E₂ to accelerate oviductal transport of oocytes in cycling rats involves successive activation of the cAMP-PKA and PLC-IP3 signalling cascades and does not require activation of MAPK. These findings clearly illustrate a non-genomic pathway triggered by E₂ that regulates a complex physiologic process accomplished by an entire organ.

This article has been cited by other articles:

				A. Parada-Bustamante, P. A Orihuela, M. Rios, P. A Navarrete-Gomez, C. A Cuevas, L. A Velasquez, M. J Villalon, and H. B Croxatto Catechol-O-Methyltransferase and Methoxyestradiols Participate in the Intraoviductal Nongenomic Pathway Through Which Estradiol Accelerates Egg Transport in Cycling Rats Biol Reprod, December 1, 2007; 77(6): 934 - 941. [Abstract] [Full Text] [PDF]