Transferrin-mediated uptake of plutonium by spermatogenic tubules.

Using isolated rat seminiferous tubules as an in vitro model, we have found that 238Pu can cross the blood-tubule barrier and accumulate within tubules in a time dependent manner. Furthermore, similar to 59Fe, tubule 238Pu uptake was inhibited by the addition of excess transferrin, suggesting that plutonium may utilize the physiological iron-transferrin pathway to cross the blood-tubule barrier. However unlike 59Fe, 238Pu was only transiently associated with the tubules, suggesting differences in the intracellular processing of these radionuclides. The assumptions made in the estimation of doses to the human testis from incorporated plutonium are considered.