Andrew A. Rooney

Serum Concentrations of Various Environmental Contaminants and Their Relationship to Sex Steroid Concentrations and Phallus Size in Juvenile American Alligators

Abstract. Recent studies have reported a number of abnormalities in the hatchling and juvenile alligators of Lake Apopka, FL (USA). These abnormalities include modifications of plasma concentrations of sex steroids in males and females as well as abnormalities in gonadal morphology, gonadal enzyme activity, and steroidogenesis. Embryonic exposure to environmental contaminants in the eggs has been hypothesized to be the causal agent for these changes. However, posthatchling exposure can also contribute to changes in reproductive and endocrine functioning. We have detected serum concentrations of 16 of 18 organochlorine pesticides or metabolites (OCs) and 23 of 28 congener-specific polychlorinated biphenyls (PCBs) examined in juvenile alligators from Lake Apopka, Orange Lake, and Lake Woodruff National Wildlife Refuge. Lake Apopka juveniles had significantly elevated serum concentrations of p,p′-DDE, dieldrin, endrin, mirex, oxychlordane, ΣDDTs, and ΣPCBs compared to juveniles from the other lakes. Further, we observed no correlations between serum contaminant concentrations and sex steroid concentrations (estradiol-17β and testosterone). However, serum testosterone was significantly lower in males from Lake Apopka and Orange Lake compared to Lake Woodruff NWR. We did not observe relationships between phallus size or other body parameters and serum contaminant levels. Phallus size was smaller in males from Lake Apopka even after adjustment for body size. We suggest that the observations previously reported for juvenile alligators—and observed again in this study—are apparently not associated with the current serum levels of the environmental contaminants we measured, but could be due to exposures during embryonic development to these or other pollutants. Future studies must determine if a causal relationship exists between the contaminants found in alligator eggs and abnormalities observed in the hatchlings and persisting in juveniles.

Biology of stress: interactions with reproduction, immunology and intermediary metabolism

Animals must maintain a steady physiological state, homeostasis, in response to a changing environment. An understanding of the stress response is essential if one is to appreciate the complex physiological mechanisms maintaining homeostasis in vertebrates. Moreover, a comprehensive understanding of the biology of stress is essential if we are to reduce stress in the care of any vertebrate species, including those that are not domesticated and traditional laboratory animals.

Effect of Acute Stress on Plasma Concentrations of Sex and Stress Hormones in Juvenile Alligators Living in Control and Contaminated Lakes

Environmental contaminants can act as stressors, inducing elevated circulating concentrations of stress hormones such as corticosterone and corticod sol. Development in contaminated eggs has been reported to modify circulating sex steroid hormone concentrations in alligators (Alligator mississippiensis). We ex- amined plasma concentrations of testosterone (T), estradiol-17p (E2), and corticosterone (B) immediately upon and two hours after capture in male and female juvenile alligators living in either contaminated or relatively pristine lake systems. We observed that plasma T concentration was significantly depressed in males from the contaminated lake, whereas plasma E2 showed significant variation between sexes but not between lakes. Initial plasma B concentrations were similar between alligators from both lakes or either sex. Two hours of capture and restraint did not effect plasma T or E2 concentrations but was associated with a dramatic rise in plasma B concentrations. These data suggest that juvenile alligators exposed to contaminants in ovo are apparently unaffected in their rapid glucocorticoid response to acute stress.

Steroid Hormones as Biomarkers of Endocrine Disruption in Wildlife

Xenobiotic compounds introduced into the environment by human activity have been shown to adversely affect the endocrine system of wildlife. Various species exhibit abnormalities of (1) plasma sex steroid hormones, (2) altered steroid synthesis form the gonad in vitro and (3) altered steroidogenic enzyme function. These endpoints are sensitive and relatively easy to measure quantitatively with reliability and precision. These observations have led to the conclusion that sex steroid hormones could be markers of exposure to, and altered function from, endocrine disrupting contaminants (EDCs). However, there are serious limitations in the use of steroid hormones as generalized markers of EDC exposure. Steroid hormones exhibit seasonal, ontogenetic, gender and species-specific variation. Moreover, the regulation of sex steroid plasma concentrations is a relatively complex phenomenon capable of short-term (minutes-hours) alteration due to environmental inputs, such as acute stress--an activational response. Alterations in steroids synthesis and degradation also can be a response to altered embryonic development due to EDC exposure--an organizational response. If steroid hormones are to be used as biomarkers, then closely controlled, well designed sampling has to be performed. Additionally, an appreciation of the variation possible in endocrine responses among the species to be studied must be obtained.

Recent progress and diverse effects in developmental immunotoxicology: overview of a symposium at the 46th Annual SOT Meeting, Charlotte, NC

It has long been known that the developing immune system is more sensitive and susceptible than the adult immune system to some drugs and environmental contaminants. However, notable advances have been made in the database of studies supporting developmental immunotoxicity (DIT) over the past 5 years. There is considerable evidence that responses of the immune system can be quantitatively or qualitatively different from normal adult responses when xenobiotic exposure occurs during critical periods of immune system development. Qualitative differences of DIT relative to adult exposures include examples of more persistent effects, a latency of effects, and immune dysfunction that is fundamentally different than effects observed when adults are exposed. A symposium was presented at the Society of Toxicology annual meeting to provide an update on advances in the maturing field of developmental immunotoxicology and to facilitate discussion on the range of DIT and later life effects following developmental exposure. In particular, presentations focused on implications of neuroendocrine cross-talk for DIT, the association between developmental air pollutant exposure and asthma, and recent evidence that developmental exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin may increase the risk of autoimmune responses. Several important concepts relative to DIT assessment were illustrated, i.e., (1) Screening for immunosuppression alone is not sufficient to identify all potential immunotoxic effects; (2) DIT cannot be reliably predicted from studies that only utilize adult exposures; (3) Functional testing protocols are preferred in the assessment of DIT; (4) Gender-related differences should be routinely assessed; (5) Latency (i.e., later-life adverse outcomes resulting from developmental exposures) is an important consideration that cannot be detected in adult exposure studies; and, (6) There is increasing support for DIT testing protocols with continuous exposure throughout development until the immune assay is performed.