Atrazine exposure and reproductive function of ranid frog species collected in Michigan

The triazine herbicide atrazine has been suggested to be a potential disruptor of normal sexual development in male frogs. The goals of this study were to collect native ranid frogs from agricultural and non-agricultural areas and examine gonadal gross morphological and histology, plasma steroid hormone concentrations and aromatase activity. Liver enzyme activities were also measured to determine whether atrazine exposure affected enzymes functioning in hormone metabolism.; Juvenile and adult green frogs (Rana clamitans), bullfrogs (R. catesbeiana) and leopard frogs (R. pipiens) were collected in the summers of 2002 and 2003 from agricultural and non-agricultural areas in south central Michigan. Atrazine concentrations were below the limit of quantification at most non-agricultural sites. Concentrations did not exceed 2 mug/L at most agricultural sites. One concentration of 250 mug atrazine/L was measured once at one site in 2002. Hermaphroditic individuals were found at a low incidence at both non-agricultural and agricultural sites in both adults and juveniles. Testicular oocytes (TOs) were found in frogs at most of the sites, with the highest incidence occurring in juvenile leopard frogs. TO incidence was significantly different between agricultural and non-agricultural sites in juveniles in 2003, and was correlated with atrazine concentrations. Neither the incidence of hermaphroditism nor TO incidence was correlated with atrazine exposure in the other adults and juveniles collected.; Plasma steroid concentrations varied among locations. Aromatase activity was measurable in less than 11% of testes in adult males, and less than 4% of testes in juvenile males. Aromatase activities were up to 2.5-fold higher in juvenile than adult females. No relationships were found between atrazine concentrations measured in water at the sites and the hormone parameters measured. LSI values in adult male frogs were significantly greater at agricultural sites. Atrazine concentrations were significantly and negatively correlated with MROD activity in adult male green frogs. LSI and EROD and MROD activities were not significantly correlated with atrazine concentrations in adult female or juvenile green frogs.; The results of this study indicate that atrazine exposure is not correlated with gross morphological or histological gonad abnormalities or with an increase in aromatase activity in male ranid frogs.