The composition of luminal plasma from the cauda epididymidis of rabbits has been investigated after prolonged retention of spermatozoa in the cauda epididymidis of entire animals, and of castrated animals both with and without hormone replacement. The morphology of the contained spermatozoa and the epididymal cells has also been examined.
In the presence of androgen, spermatozoa survived for 4 to 5 weeks before degenerative changes became apparent and the composition of the epididymal plasma and the histological characteristics of the lining cells were not seriously affected during this period. The only change in the plasma which could be due to sperm death was an increase in the lactic dehydrogenase (LDH) activity. After androgen withdrawal, spermatozoa degenerated rapidly and there were considerable changes in the composition of the luminal plasma. There was a rapid increase in the level of sodium ions and pH, and a decrease in the concentrations of glycerylphosphorylcholine (GPC) and protein. The activity of acid phosphatase and LDH also decreased. Initially, the concentration of inorganic phosphate and potassium increased but this was soon followed by a decrease. Five weeks after castration, all the spermatozoa disappeared from the epididymis and the epididymal cells had regressed. If testosterone replacement was given at this stage, the level of sodium ions in the plasma decreased and the concentration of GPC increased. The epididymal cells were also restored to their normal histological appearance.
These results provide evidence that, in the presence of androgen, the epididymal cells in the cauda epididymidis actively maintain a constant milieu in the lumen of the duct by their capacity for absorption and secretion. If androgen is withdrawn, these functions cease and considerable changes take place in the lumen.
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