Progesterone Is a Sperm-Releasing Factor from the Sperm-Storage Tubules in Birds

Abstract

Because of the presence of sperm-storage tubules (SST) in the utero-vaginal junction (UVJ) in the oviduct, once ejaculated sperm have entered the female reproductive tract, they can survive for a prolonged time in domestic birds, although the specific mechanisms involved in the sperm uptake into, maintenance within, and controlled release from the SST remain to be elucidated. In this report, we provide evidence that progesterone triggers the release of the resident sperm from the SST in the UVJ. The ultrastructural observation of the SST indicated that the resident sperm are released from the SST around 20 h after oviposition. When laying birds were injected with progesterone, most of the sperm were released from the SST within 1 h of injection. In situ hybridization analyses demonstrated the presence of the transcripts of membrane progestin receptor α in the UVJ, and the translated proteins were detected in the UVJ extracts by Western blotting. Moreover, the number of secretory granules in the SST epithelial cells fluctuates during the ovulatory cycle, and the progesterone administration mimics this phenomena. A binding assay using [(3)H]-progesterone indicated the presence of a high affinity, limited capacity, saturable and single binding site for [(3)H]-progesterone in the membrane fraction of the UVJ, and this receptor did not interact with the synthetic antiprogestin RU486. These results demonstrated for the first time that the progesterone stimulates the release of the resident sperm from the SST and that the release of the sperm might occur via membrane progestin receptor α-mediating signal transduction.

Conservation of Avian Genetic Resources

“…Recently, progesterone has been shown to be a key factor that controls sperm release from SSTs in chicken (Ito et al, 2011). Therefore, future studies should be directed toward unveiling the physicochemical factors involved in sperm storage in and release from the SST, providing new scope regarding the fertility duration in avian reproduction.…”

Expression of Prolactin Receptor on the Surface of Quail Spermatozoa

“…Females were decapitated and the utero-vaginal junction (UVJ) of the oviduct was dissected according to the method of Ito et al (2011). The testis was isolated from mature male after decapitation.…”

Artificial Insemination in Poultry

“…The observations that receptors for estrogen and progesterone exist in the SSTs has led to the suggestion that these compounds may trigger release of resident sperm, possibly in response to hormonal cues over the course of the ovulatory cycle [50][51][52]. However, an alternate theory suggests the inherent mobility of the sperm plays a larger role than hormonal induction in egress of sperm from SSTs [9].…”