Reduction in fluid secretion by rat testis by drugs that block potassium channels

The effect of two class III antiarrhythmic drugs (Almokalant, Astra-Hässle and Dofetilide, Pfizer) on fluid secretion by rat testes has been examined. Both drugs reduced fluid secretion, whether this was measured by the amount of rete testis fluid that could be collected 22 h after unilateral efferent duct ligation, or by the difference in mass between the ligated and unligated testes, or by the difference in amount of supernatant fluid after the parenchyma of the ligated and unligated testes had been dispersed and centrifuged. The secretion of potassium, calculated from the amount of potassium in the supernatant fluids from the ligated and unligated testes was also reduced by the drugs, whereas the secretion of androgen-binding protein and inositol was unaffected. The concentration of potassium in the secreted fluid, calculated from the amount and composition of the supernatant fluids, was not affected by treatment of the rats with Almokalant, but was increased in rats treated with Dofetilide and, in these, the concentration of sodium was reduced and that of magnesium and inositol was increased and the concentration of total protein was unaffected. The concentration of androgen-binding protein in secreted fluid was increased in rats treated with Almokalant, while the concentration of testosterone was unaffected. Histological examination of testes from treated rats revealed phagocytosis of stage 19 spermatids in tubules at stages VIII-IX after 2 days, at stages IX-XI after 4 days and at stages VIII-XIV after 7 days, apparently owing to an effect on spermiation. It appears that these drugs interfere with potassium-mediated fluid secretion by the testis, leading to the other changes seen.