REPRODUCTIVE IMPAIRMENT AND INDUCTION OF ALKALINE-LABILE PHOSPHATE, ABIOMARKER OF ESTROGEN EXPOSURE, IN FATHEAD MINNOWS (PIMEPHALES-PROMELAS) EXPOSED TO WATERBORNE 17-BETA-ESTRADIOL

The objectives of this research were: (1) to assess the effects of wat erborne 17 beta-estradiol [E2 (17 beta)-estra-1,3,5(10)-triene-3,17-di ol; CAS RN 50-28-2] on the reproduction of fathead minnows (Pimephales promelas) as a benchmark to which xeno-estrogens can be compared, and (2) to correlate the effects on reproductive function with plasma vit ellogenin expression, measured as alkaline-labile phosphorous. Histopa thological changes were also noted but are reported elsewhere. Duplica te groups of six fish (3 male and 3 female) were exposed to waterborne E2 at nominal concentrations of 10, 1, and 0.1 nM (2724, 272.4, and 2 7.24 ng l(-1)) administered via a flow-through proportional diluter ap paratus for 19 days. An ethanol carrier solvent was used at a final ta nk concentration of 1 ppm v/v in the treated tanks and in the solvent control tanks, the latter did not receive E2. Duplicate control tanks received neither ethanol nor E2. Dissolved E2 concentrations, measured throughout the exposure period using an ELISA, averaged 79% of nomina l concentrations in the treated tanks. ELISA-detectable concentrations of E2 were found in all tanks (ranging from 3.5 to 15 ng E2 l(-1)), i ncluding the control and solvent control tanks, which indicated that f ish in the untreated tanks may have been the source of some E2. The EC 50 (concentration expected to cause 50% effect), based on measured E2 concentrations, for inhibition of egg production was 120 ng E2 l(-1) ( log(10) EC50 = 2.08 +/- 1.22, +/- S.E.). The EC50 for induction of vit ellogenin (measured as plasma alkaline-labile phosphate) in males was 251 ng E2 l(-1) (log(10) EC50 = 2.40 +/- 0.33, +/- S.E.). No vitelloge nin induction plateau was observed in females, therefore no EC50 could be calculated. Egg production, expressed as eggs laid per female, was significantly correlated with plasma vitellogenin in both males (line ar r(2) = 0.46, P < 0.03) and females (linear r(2) = 0.81, P < 0.0004) , though the relationship was stronger with female plasma vitellogenin expression than with males. The primary effect of E2 exposure on fema le fathead minnows appeared to be alteration of the tinting of recrude scence including vitellogenin production. Spawning tvas inhibited in a way that indicated that exposure to waterborne E2 may have 'reset' th e cycle oi recrudescence toward tint: beginning of the oogenic cycle. Vitellogenin induction in male fathead minnows was strongly correlated with E2 exposure: but less so with egg production. The results of thi s experiment link a biochemical indicator of waterborne estrogen expos ure, vitellogenin, with a reproductive performance indicator. egg prod uction, an important parameter affecting fish populations in the envir onment. (C) 1998 Elsevier Science B.V. All rights reserved.