Turtle sex determination assay: Mass balance and responses to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin and 3,3′,4,4′,5‐pentachlorobiphenyl

Abstract

Polyhalogenated hydrocarbons have been implicated in the anomalous sexual differentiation of mammals and reptiles. Here, a temperature-sensitive turtle sex determination assay using the red-eared slider (Trachemys scripta elegans) was used to determine the estrogenic or antiestrogenic activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3,3',4,4',5-pentachlorobiphenyl (PCB-126). Neither TCDD nor PCB-126 showed a statistically significant difference in the resulting sex ratios (Fisher's exact test, p < 0.45). As a consequence of the dosing technique (eggshell spotting), the shell retained 90 and 96% of the dose for PCB- 126 and TCDD, respectively, similar to retention of estradiol- 17beta. However, the dosing allowed transfer of sufficient chemical to achieve tissue concentrations that were greater than most concentrations reported for environmentally incurred residues. Similar relative mass distributions of PCB-126 and TCDD were observed in albumin (14-20%), yolk (55-70%), and embryo (16-25%). Relative concentration distributions in the embryo approached those in the yolk, 37 to 40% and 40 to 52%, respectively, while relative concentrations in the albumin remained at 11 to 20%. Lipid-normalized TCDD and PCB-126 concentrations were 30- to 40-fold greater in the embryo than in the yolk. It is hypothesized that nonpassive partitioning processes may have occurred in the embryo.

Dose verification after topical treatment of alligator (Alligator mississippiensis) eggs

“…The percent transfer was highest for the lowest DDE doses applied, suggesting that the physical mechanism of OCP transport across the eggshell and membrane might be optimal at lower concentrations. Consistent with our results, studies employing turtle eggs indicate that only a small proportion of the applied chemical is transferred into the egg contents (4-34%), and an even smaller proportion partitions into the embryo (0.2-8%) [6,[9][10][11]. The low transfer rates reported for turtle eggs (soft and thin) and alligator eggs (hard and thick) suggest this could be a general characteristic of reptilian eggs unrelated to eggshell structure.…”

“…Most published egg exposure studies have applied substances topically (surface painting) with various vehicles (ethanol, acetone, dimethylsulfoxide [DMSO]) in differing volumes, all of which produced low mortality [8]. Only a few published reports have measured the transfer of topically applied substances into the egg, and each has found it to be low and highly variable [6,9–11]. Because interpreting a chemical effect on hatchling sex ratio requires a measurement of internal chemical dose [10,11], we first attempted to validate a chemical delivery method as a prelude to further dose‐response studies with chemical mixtures.…”

“…Only a few published reports have measured the transfer of topically applied substances into the egg, and each has found it to be low and highly variable [6,9–11]. Because interpreting a chemical effect on hatchling sex ratio requires a measurement of internal chemical dose [10,11], we first attempted to validate a chemical delivery method as a prelude to further dose‐response studies with chemical mixtures. Here, we report measurements of mortality and chemical transfer after injection or topical application of various organochlorine pesticides (OCPs) to American alligator ( Alligator mississippiensis ) eggs.…”

A cohort study of in utero polychlorinated biphenyl (PCB) exposures in relation to secondary sex ratio

“…As PCB blood concentrations have been shown to remain very stable during pregnancy [ 37 ], these findings suggest that high maternal PCB concentrations, at least for some congeners, may either favor the fertilization by female sperm, or result in greater male embryonic or fetal losses. Sex ratio alterations or decreased survival of wildlife in association with organochlorine exposures have been well documented [ 38 - 41 ], although not all studies have confirmed such findings [ 42 ].…”

Environmental Endocrine Disruption of Brain and Behavior

“…Studies have established that, both for aquatic and groundwater environments, contamination penetrates into the egg resulting in EDC profiles in the yolk that match those of the surrounding environment (cf. Bishop et al, 1998;Gale et al, 2002;Halldin, 2005;Heinz et al, 1991;Peterman et al, 1996;Podreka et al, 1998).…”