248 DISTRIBUTION OF OVULATION-INDUCING FACTOR IN MALE REPRODUCTIVE TISSUES OF LLAMAS

Abstract

We have recently reported that the ovulation-inducing factor (OIF) in seminal plasma is the well-conserved neurotrophin, nerve growth factor. This protein has been identified in the ejaculates of a variety of species using both in vivo and in vitro bioassays. The role of OIF in the ejaculate is evident in camelids. Irrespective of whether a male is intact or vasectomised, ejaculation of this protein during copulation stimulates an increase in circulating LH in the female, which subsequently leads to ovulation. The purpose for OIF in species that are spontaneous ovulators, however, remains unclear. We hypothesise that OIF production is restricted to the secretory epithelium of accessory glands of the male, specifically the prostate gland, because of its conservation among mammals. The objective of the present study was to determine the sites of OIF secretion in the llama that contribute to high concentrations found in the ejaculate. The mucosa, submucosa, and muscularis layers of the reproductive organs (testis, epididymis, ductus deferens, and penis) and accessory sex glands (ampulla, prostate gland, and bulbourethral gland) from mature male llamas (n = 2) were probed with polyclonal rabbit anti-nerve growth factor. The secondary antibody used was horseradish peroxidase-conjugated goat-anti-rabbit immunoglobulin G. The distribution and intensity of OIF-secreting cells were identified and compared among tissues using a four-point scale. The quantity of OIF detected was highest in mucosal prostatic cells. The protein was strongly localised in the apical region of epithelial cells and frequently found within the glandular lumen. The seromucus-secreting epithelium of ampullary glands showed no reaction to OIF, whereas the bulbourethral gland epithelium showed an intermediate response. The presence of OIF was not detected in the epithelium of the penile urethra, epididymis (caput, corpus, or cauda), or seminiferous tubules. A diffuse distribution of the protein was, however, detected in the stroma of the testes, epididymides, and accessory glands. We conclude that cells that secrete OIF are distributed unequally among accessory sex glands in llamas. The bulk of OIF is produced by the prostate gland, with minimal to no contributions by the bulbourethral and ampullary glands. Future studies involve species comparisons and relating the size of the prostate gland to the concentration of OIF within an ejaculate.

Research supported by the Natural Sciences and Engineering Research Council of Canada.