TESTICULAR SEROTONIN IS RELATED TO MAST-CELLS BUT NOT TO LEYDIG-CELLSIN THE RAT

Testicular serotonin (5HT) concentrations were determined by HPLC in t he testes of rats treated neonatally with oestradiol benzoate (EB) and in adult rats treated with the Leydig cell cytotoxic ethylene dimetha ne sulphonate (EDS). 5HT concentrations were related to mast cell numb ers. EB-treated rats showed an accumulation of mast cells in the teste s at 35 and 70 days of age and increased 5HT concentrations in both th e interstitial fluid and the testicular capsule, whereas no increases in 5HT concentrations or in the number of mast cells were found for th e ventral prostate of these animals. On the contrary, 5HT concentratio ns were not related to the number of Leydig cells. In EB-treated rats, in which Leydig cells were nearly absent at 35 days of age, 5HT conce ntrations were significantly increased. Furthermore, EDS-treated rats did not show significant changes in 5HT concentrations, in spite of th e elimination of Leydig cells. These data suggest that mast cells are a major source of serotonin in the rat testis.