Immunohistochemistry of secretory proteins in the bull seminal vesicle.

Antibodies against several proteins isolated from bovine seminal fluid (ribonucleases, bull seminal proteinase inhibitor BUSI II, seminal antimicrobial protein SAP) were used to identify the secretion sites of the respective proteins within the genital tract of the bull. Consistent positive immunoreactions were achieved with most of the antisera in the seminal vesicle epithelium, while only weak or dispersed immunoreactions were found in the epididymis, ductus deferens or the prostate. Comparison of serial sections of bull seminal vesicle stained with different antisera gave incongruous distribution patterns of positively reacting cells. This was interpreted as a sign of either a differential secretion cycle for different proteins in these cells or, more likely, a fixation or processing artifact. There was no clear cut evidence for secretion of seminal antimicrobial protein by seminal vesicle epithelium, but rather a resorption of intraluminally concentrated SAP. The secretion site of this important protein remains obscure, unless cRNA probes for in situ hybridisation studies are available.