Organochlorines Affect the Major Androgenic Hormone, Testosterone, in Male Polar Bears ( Ursus Maritimus ) at Svalbard

Abstract

Normal sexual development and subsequent reproductive function are dependent on appropriate testosterone production and action. The regulation of steroid hormones, including androgens, can be influenced by both biological and environmental factors, including environmental chemicals. Concentrations of organochlorines are considerably greater in Svalbard polar bears than in polar bears from other regions. Between 1995 and 1998, samples were collected from 121 male polar bears (Ursus maritimus) from the Svalbard area. In this study, testosterone concentration variations were described for male polar bears during different seasons and for all age groups. To study possible relationships between plasma testosterone concentrations and biological factors, such as age, axial girth, and extractable plasma fat, and organochlorine contaminants including hexachlorocyclohexanes, hexachlorobenzene, chlordanes, p,p'-DDE, and 16 individual polychlorinated biphenyl (PCB) congeners, identical statistical analyses were performed on the total population and a subsample of reproductively active adults. Of the biological factors, axial girth showed a significant positive relationship and percentage extractable fat and a significant negative relationship with the testosterone concentrations. Both the epsilon pesticides and epsilon PCBs made significant negative contributions to the variation of the plasma testosterone concentration. The continuous presence of high concentrations of organochlorines in male polar bears throughout their life could possibly aggravate any reproductive toxicity that may have occurred during fetal and early postnatal development.

Internal exposure to pollutants and sex hormone levels in Flemish male adolescents in a cross-sectional study: associations and dose–response relationships

“…Rylander et al (2006) found no associations between serum PCB153 and testosterone concentrations in middle-aged and elderly men. In male polar bears, serum PCB levels are associated with lower serum testosterone levels (Oskam et al, 2003). The differences between our observations and most published data might, however, at least in part, stem (see also below) from the fact that our observations relate to relatively low concentrations, which are much lower than those that occurred during the Yucheng incident and than the concentrations used in animal experiments.…”

“…The differences between our observations and most published data might, however, at least in part, stem (see also below) from the fact that our observations relate to relatively low concentrations, which are much lower than those that occurred during the Yucheng incident and than the concentrations used in animal experiments. The PCB concentrations in the polar bears (Oskam et al, 2003) were more than hundred times higher than in the Flemish adolescents in our study. The biological plausibility of our observations might rest on the anti-estrogenic activity of PCBs (Kruger et al, 2008), as endogenous estrogens inhibit testosterone production through actions on the testis or indirectly on the hypothalamic-pituitary axis (Sanford, 1985;Delbes et al, 2005).…”

Effects of long-term maternal exposure to low doses of PCB126 and PCB153 on the reproductive system and related hormones of young male goats

“…In the male population of Florida panthers (Felix concolor coryi) sperm abnormalities, including low ejaculate volume and sperm concentration, poor sperm motility and a high proportion of abnormal sperm, as well as an increase in cryptorchidism, have been reported (Facemire et al 1995). A decrease in plasma testosterone levels has been reported for juvenile alligators (Alligator mississipienisis) in Lake Apopka, Florida, as well as in polar bears (Ursus maritimus) from the Svalbard area in the Norwegian Arctic , Oskam et al 2003. It is not easy to compare and integrate results from wildlife studies since data that report possible relationships between PCB exposure and adverse reproductive effects are often based upon a diversity of species, different exposure conditions, and differences in exposure levels and timing and duration of the exposure.…”

Chlorinated hydrocarbon contaminants and metabolites in polar bears (Ursus maritimus) from Alaska, Canada, East Greenland, and Svalbard: 1996−2002

“…Studies dealing with the effects of CHCs on polar bear health have raised significant concerns. As recently summarized by Fisk et al (2005-this issue), the current understanding of contaminant-induced biological effects in polar bears points to evidence that chronic exposure to CHCs and their metabolites may compromise endocrine functions and homeostasis (Sandau, 2000;Norstrom, 2000;Skaare et al, 2001a;Letcher et al, 2002;Haave et al, 2003;Oskam et al, 2003Oskam et al, , 2004Braathen et al, 2004), immune functions (Bernhoft et al, 2000;Norstrom, 2000Norstrom, , 2001Skaare et al, 2001b;Larsen et al, 2002;Lie et al, 2004aLie et al, , 2005Kirkegaard et al, 2005), cub and reproductive female survival , reproduction and development (Wiig et al, 1998), and hepatic P450-enzymes induction (Bandiera et al, 1995;Letcher et al, 1996).…”