Acidification of epididymal fluid in the boar

The present study describes the measurement of pH made in vivo in the rete testis fluid and in different regions of the boar epididymis. Furthermore, samples of whole ejaculates, semen fractions, testicular (ductuli efferents/rete testis), epididymal and deferential fluids collected from the same fertile boars, were analysed for their acid/base status with an automatic blood gas analyser. A pH gradient of activity was found between the fluid entering the ductus epididymis (pH 7.2) and the region of sperm storage at the cauda (pH 6.5). A significantly lower concentration of bicarbonate ion was found in the cauda epididymidis (3-4 mM) compared to rete testis fluid (30 mM), which might be related to the quiescence of the spermatozoa. A significant increase in extracellular pH and bicarbonate concentration occurred at ejaculation, the bicarbonate levels being 9-10-fold higher in the semen fraction rich in seminal vesicle fluid, where sperm showed higher motility, than in the cauda epididymis.