Uptake of rhodamine 6GO into a specific zone of the mouse epididymis

Doses (2.5 mg/kg) of rhodamine 6GO were given subcutaneously to five Charles-Rivel mice. After 15 minutes the testis and epididymis were observed with a fluoroscope and a fluorescent microscope which showed that rhodamine 6GO was present in a rhodamine-fluorescent zone (RF-zone) of the caput epididymidis. In this RF-zone, the fluorochrome was localised in the epithelial cells of the epididymal duct but not in the lumen nor the vascular system. At the edge of the RF-zone a wide band of connective tissue was present; the epithelium of the epididymal duct in this zone was higher and its tubular diameter greater than in the rest of the epididymal duct and spermatozoa were usually not present in the lumen. A possible role played by the epididymis in the endocrine control of the testicular function is suggested.