Dose-response and time course relationships for vitellogenin induction in male western fence lizards (Sceloporus occidentalis) exposed to ethinylestradiol.
The long-term goal of this research is to develop and validate an in vivo reptile model for endocrine-mediated toxicity using fence lizards (Sceloporus spp.). One of the best defined estrogenic responses in oviparous vertebrates is induction of the yolk precursor protein, vitellogenin (Vtg). In this study, dose-response and time course relationships for Vtg induction were determined in male western fence lizards (Sceloporus occidentalis) given intraperitoneal injections of 17alpha-ethinylestradiol (EE2). Plasma Vtg was quantified directly with an antibody-capture enzyme-linked immunosorbent assay (ELISA) and indirectly using plasma alkaline-labile phosphate (ALP) in order to compare these two methods. Both ELISA and ALP predicted similar median effective dose (ED50 [dose causing a 50% maximal response]) values for plasma Vtg induction (0.167 mg/kg for ELISA and 0.095 mg/kg for ALP). In addition, both ELISA and ALP detected significant Vtg induction at a dose of 0.0003 mg/kg of EE2, which was the lowest dose used in our study. A decrease in body weight at the highest dose (10 mg/kg) and an increase in hepatosomatic index at the four highest doses were observed. Serial dilutions of plasma from an EE2-exposed male revealed a high correlation between plasma Vtg and ALP determinations in this species. In conclusion, our data show that plasma ALP may be a suitable alternative for measuring plasma Vtg compared with developing a Vtg ELISA in fence lizards exposed to estrogenic compounds.
Brasfield
Sandra M
SM
Department of Zoology, Oklahoma State University, Stillwater 74078, USA.
Weber
Lynn P
LP
Talent
Larry G
LG
Janz
David M
DM
D000818:Animals; D015415:Biomarkers / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004703:Endocrine System / Q000187:drug effects*; D004797:Enzyme-Linked Immunosorbent Assay; D004958:Estradiol / Q000633:toxicity; D045166:Estradiol Congeners / Q000633:toxicity*; D004997:Ethinyl Estradiol / Q000633:toxicity*; D007274:Injections, Intraperitoneal; D008116:Lizards / Q000097:blood / Q000378:metabolism*; D008297:Male; D008954:Models, Biological; D013997:Time Factors; D018675:Toxicity Tests / Q000379:methods*; D014819:Vitellogenins / Q000096:biosynthesis* / Q000097:blood
D015415:Biomarkers; D045166:Estradiol Congeners; D014819:Vitellogenins; D004997:Ethinyl Estradiol; D004958:Estradiol