Flow cytometric Differentiation of Testis Cells after Administration of TBTO and TPT to Rats

The environmental pollutants and endocrine disrupting chemicals tributyltin oxide (TBTO) and triphenyltin (TPT) are well known for their deleterious effects on reproductive organs in invertebrates as well as in mammals. An in vivo study covering the whole pubertal period was performed on young male Wistar rats to investigate the effects of postnatal exposure on the male reproductive system [1]. TBTO and TPT were administered daily by oral gavage at dose levels of 0.5 and 15 mg/kg body weight (TBTO) or 2, 6, and 12 mg/kg bw (TPT) from postnatal day 23 to 53. Two control groups were treated with the vehicle (peanut oil) only. A positive control group received methyltestosterone (MTT) at a dose level of 40 mg/kg bw/day. At necropsy, the testes were weighed and the left one subjected to flow cytometric analysis (FCM) of the cellular DNA content. Testis cells were prepared and the DNA stained with propidium jodide [2]. FCM yielded in four peaks representing tetraploid (mainly primary spermatids), diploid (comprising primary and secondary spermatocytes, spermatogonia and somatic cells) and two haploid (immature and mature spermatids) cell populations. Mean absolute testis weight was significantly decreased after administration of TPT at all dose levels and the high dose of TBTO. Most severe reduction was observed following exposure to MTT [1]. In the group treated with MTT, the relative amount of haploid cells was significantly decreased. A concomitant increase in diploid and tetraploid cells suggested an inhibition of spermatogenesis by an excess concentration of this hormone. In contrast, treatment with TBTO and the low dose of TPT did not alter the amount of cells in the different populations as compared to the controls. However, the high and intermediate doses of TPT produced a diminished amount of haploid and an increased percentage of diploid and tetraploid cells supporting previous findings of severely impaired spermatogenesis and fertility [3]. The mechanism behind these effects needs to be further elucidated.