PARENT SESSION

PM10 Mechanisms of Toxic Action
Exhibit Hall
8:00 AM - Monday

(PM168) Effects of aryl hydrocarbon receptor activation on gondal development in zebrafish.

Driedger, K.¹, Heather, B.¹, Weber, L.^{1, 2}, Janz, D.^{1, 2}, ¹ University of Saskatchewan, Toxicology Centre, Saskatoon, Saskatchewan, Canada² University of Saskatchewan, Veterinary Biomedical Sciences, Saskatoon, Saskatchewan, Canada

ABSTRACT- The aryl hydrocarbon receptor (AhR) may be involved in normal gonadal differentiation and development in mammals and exogenous activation of AhR has been reported to inhibit estrogen-mediated responses and ovarian development. Exposure to AhR agonists during the period of sexual differentiation (day 10-40 post hatch) may interfere with normal growth and sexual development. Effects on sexual development may be due to the gonad′s lesser ability to upregulate the HSP70 family in response to chemical stress. The CYP1A family of proteins is a known AhR gene product, and may be used to indicate exposure to an AhR agonist. The objective of this research was to investigate the effects of AhR activation during the period of sexual differentiation in zebrafish. Growth and condition factors, gonadal sex ratio, whole body protein concentration, HSP70 and CYP1A protein family expression were measured following exposure to the relatively non-toxic AhR agonist, -napthoflavone (BNF) from 10-40 days post hatch (dph). Treatment groups consisted of a control (solvent only), low dose (0.01 mg/L BNF) and high dose (0.1 mg/L BNF) aqueous exposures. There was a positive, significant relationship between BNF concentration and condition factor. A significant, negative relationship between BNF concentration and mean body length was detected. Whole body protein concentration was increased in treatment groups over the control, but was only significant in the low dose group. Expression of the HSP70 protein family was significantly and negatively correlated with concentration. Determination of CYP1A expression was unsuccessful due to high background and low cross reactivity between antibody and test animal. In Summary, stimulation of the AhR during sexual differentiation in zebrafish alters condition factor, whole body protein concentration and HSP70 expression.

Key words: sexual differentiation, AhR, HSP70