Long‐term effects of triethylenemelamine exposure on mouse testis cells and sperm chromatin structure assayed by flow cytometry

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Abstract
The toxic and potentially mutagenic actions of triethylenemelamine (TEM) on mouse body and testis weights, testicular cell kinetics, sperm production, sperm head morphology, and sperm chromatin structure were assessed in two experiments. The first experiment examined effects of four dose levels of TEM, assayed 1, 4, and 10 wk after toxic exposure. In the second study, effects from five dosage levels were measured at 1, 4, and 10 wk, and the highest dosage level was evaluated over 44 wk. TEM produced an expected dose related loss of spermatogenic activity and subsequent recovery as determined by dual‐parameter (DMA, RNA) flow cytometry (FCM) measurements of testicular cells. Both testicular weights and caudal sperm reserves remained generally below controls after 44 wk recovery following exposure to the highest (1.0 mg/kg daily x 5) dosage. Chromatin structure alterations, defined as increased susceptibility to DNA denaturation in situ, and sperm head morphology were highly correlated (.87‐.93, P>.001) with dose and with each other. Data obtained from the sperm chromatin structure essay (SCSA) on fresh sperm was highly correlated with measurements of aliquots of the same sample collected over 44 wk, frozen, and then measured on the same day. Sperm head morphology and sperm chromatin structure remained abnormal at 44 wk for the 1.0 mg/kg TEM dosage, suggesting that the abnormalities, present long after the initial toxic response, may be a result of mutation. This study demonstrates that flow cytometry provides a unique, rapid, and efficient means to measure effects of reproductive toxins and potential mutagens.