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SERUM AND TESTICULAR TESTOSTERONE AND ANDROGEN BINDING PROTEIN PROFILES FOLLWOING SUBCHRONIC TREATMENT WITH CARBENDAZIM (MBC)
Citation:
Rehnberg, G., R. Cooper, J. Goldman, L. Jr, J. Hein, AND W. McElroy. SERUM AND TESTICULAR TESTOSTERONE AND ANDROGEN BINDING PROTEIN PROFILES FOLLWOING SUBCHRONIC TREATMENT WITH CARBENDAZIM (MBC). U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-89/211 (NTIS PB90146200).
Description:
While the general toxicity of the benzimidazole pesticides for mammals is low, one of these compounds, Carbendazim causes degeneration of testicular tissue and decreases spermatogenic activity at doses well below the LD50 value (Barnes et al., 1983). A study conducted by Carter et al. (1987) showed that treatment with 400mg/kg/d MBC resulted in severe seminiferous tubular atrophy and infertility. Since spermatogenesis is an androgen dependent process, we characterized the effects of MBC (O-400mg/kg/d) on the endocrine function of the rat testes. Following sub-chronic (85d) exposure, serum hormones (TSH, LH, FSH and Prl) were measured as were androgen binding protein (ABP) and testosterone in testicular fluids [interstitial fluid (IF) and seminiferous tubule fluid (SNF)]. In addition, the functional capacity of the Leydig cell to secrete testosterone was assessed in vitro folloving an hCG challenge. Subchronic treatment with MBC at doses of 5O-100mg/kg/d had no effect on pituitary or testicular hormone concentrations. 200/kg/d elevated the testosterone concentration in the SNF and the ABP concentration in both the IF and SNF without affecting serum testosterone or ABP concentrations. The 400/kg mg dose resulted in increased concentration of both testosterone and ABP in the IF and SNF and elevated serum ABP, with no change in serum testosterone. This endocrine profile is consistent with the testicular atrophy and "Sertoli cell-only" syndrome seen in these animals as reported by Gray et al. (in prep.). We conclude that SNF testosterone be a result of two factors, 1) increased IF testosterone concentrations and 2) decreased testosterone outflow fron the testis to the general circulation. Also, increased ABP in the IF may reflect a change in the relative secretion of ABP into the IF and the seminiferous tubules.