Morphological and histochemical effects of 2,3,7,8-tetrachlorodibenzo-p dioxin (TCDD) on marmoset (Callithrix...

The testes of marmosets (Callithrix jacchus), which had been treated with a single dose of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) (0.3 microgram to 10 micrograms/l kg body weight (BW)) were studied after 7 days using morphological and histochemical techniques. Light microscopic and electron microscopic examination revealed decreased intercellular contact in the germinal epithelium, as indicated first by enlarged intercellular spaces between the Sertoli's cells and between the Sertoli's cells and neighboring germ cells (i.e., spermatogonia and preleptotene spermatocytes), particularly in the basic compartment of the germinal epithelium. Second, decreased intercellular contact was indicated by the accumulation of premature spermatids and spermatocytes in the tubular lumen after TCDD treatment. The Sertoli's cells exhibited an increased amount of lipids, phagolysosomes, and vacuoles in their cytoplasm. Spermatids were frequently affected by TCDD, particularly during early spermiogenesis. These alterations included vacuolization of the cytoplasm and the development of additional germinal vesicles. This special effect on spermiogenesis became even more evident quantitatively by determination and counting of tubular stages in semithin sections. Tubular determination on the basis of the appearance of spermatids revealed that the ratio of tubular stages I to III became lower and that of stages V to VII became higher, dose dependently, indicating a maturation stop at the beginning of spermiogenesis caused by TCDD treatment. After TCDD treatment, Leydig's cells were morphologically unaffected, but histochemical investigations revealed decreased activity of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD). The sensitivity of the applied methods was different in view of the level of unaffection. The effect of Leydig's cells, as indicated by the decreased activity of 3 beta-HSD, had already been found at a dose of 1 microgram/kg BW TCDD, whereas clear-cut morphological and morphometrical effects were seen at 3 micrograms/kg BW for the first time. Moreover, with the special effect on spermiogenesis in marmoset monkeys, the findings demonstrate that the toxicity of TCDD on testicular morphology is species specific.