Identification of estrogen receptor protein and messenger ribonucleic acid in human spermatozoa

The processes leading to fertilization involve a series of sequential events including the deposition and transport of sperm in the female genital tract. It is becoming evident that spermatozoa in which a hyperactive state has been induced are more effective in both reaching and penetrating the oocyte. Many of the changes that spermatozoa undergo are the result of their ability to respond to the milieu of the female genital tract. In the presence of estrogen sperm have been shown to have increased their metabolic activity and flagellar activity and to have an increased ability to penetrate oocytes. Most important, these observed changes in sperm physiology occur quickly, suggesting a novel second-messenger system coupled to the estrogen receptor. Established effects of steroid hormones involve mediation of the signal through genomic expression. However, because it has not been definitively demonstrated whether the human sperm express the estrogen receptor, the mechanism by which estrogen exert its effect remains to be elucidated.

The presence of estrogen receptors on human spermatozoa was investigated. Immunohistochemistry performed on human spermatozoa indicates that the estrogen receptors are located on the tailpiece. In addition, protein from human spermatozoa was isolated and subjected to Western blot analysis.

Results indicate a single band of approximately 65 kd, similar to that of the native human estrogen receptor. Ribonucleic acid obtained from the human spermatozoa was reverse transcribed into deoxyribonucleic acid. With use of selected primers, this deoxyribonucleic acid was amplified by polymerase chain reaction. Resolution and examination of the expansion products demonstrated a single band of deoxyribonucleic acid of 450 bp, identical to that expected from the selected primers. The specificity of this reverse transcriptase-polymerase chain reaction amplified deoxyribonucleic acid sequence was verified by Southern blotting.

For the first time we provide evidence as to the expression of estrogen receptor by human spermatozoa.