Oxytocin in the semen and gonads of the stallion

It has been suggested that oxytocin is involved in sperm transport and moti lity in domestic animals. Immunoreactive oxytocin was measured in seminal f ractions (pre-ejaculatory fluid, seminal plasma, gel and sperm) and in extr acts of testis and epididymis from stallions. In addition, sections of gona dal tissue from stallions were immunostained for the presence of oxytocin a nd its neurophysin. Oxytocin was detected in all of the seminal fractions, being highest in the gel. It was also present in washed, lysed sperm and in extracts from the testis and epididymis. Immunostaining for oxytocin was p resent in occasional interstitial cells in the testis and in the epididymal epithelium and smooth muscle. However, immunostaining for neurophysin was detected in a few interstitial cells in the testis of only 1 of 8 stallions and was absent from all areas of the epididymis. These data demonstrate fo r the first lime the presence of oxytocin in stallion semen and gonadal tis sue; however, lack of immunostaining for neurophysin indicated that it was unlikely that there was local synthesis within the gonads. (C) 1999 by Else vier Science Inc.