[Application of BrdU-immunohistochemistry and lanthanum-tracer methods to the pathological evaluation of 1,3-dinitrobenzene testicular toxicity].

The pathogenesis of 1,3-dinitrobenzene (1,3-DNB)-associated testicular toxicity was investigated in Sprague-Dawley rats with 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry and lanthanum-tracer methods as well as routine histopathological examination. Animals were killed at 8, 12, 24, 48 and 96 hr after a single oral administration of 1,3-DNB at a dose of 25 mg/kg. Histopathologically, severe alterations in the testes such as degenerating pachytene spermatocytes and giant cell formation were observed by 24 hr. Immunohistochemical analysis revealed no differences in the distribution of BrdU-positive cells between treated and control rats throughout the experiment. Thus it was concluded that 1,3-DNB exerted no effects on DNA synthesis in spermatogonia and preleptotene spermatocytes. Using the lanthanum-tracer method, it was shown that although lanthanum could penetrate the intercellular space from the basement membrane, the tight junction, consisting of fusions of contiguous Sertoli cell membranes, prevented further diffusion in both control rats and those killed at 8 hr after dosing. On the other hand, at 24 hr after dosing, lanthanum penetrated into the adluminal compartment beyond the tight junctions, thus demonstrating loss of integrity of the blood-testis barrier. The results suggested that the Sertoli cell is the primary target of 1,3-DNB testicular toxicity.