BLOMQUIST, Charles H.*; LIMA, Paul H.; ATKINSON, Shannon; University of Minnesota; University of Minnesota; Alaska SeaLife Center/University of Alaska Fairbanks: Activity of Steroidogenic Enzymes in Placenta and in Lung, Fat and Skin of the Steller Sea Lion Pup (Eumetopias jubatus)
Steroidogenic enzymes that regulate levels of estrogens and androgens in mammalian tissues may be targets for endocrine disruptors. As a basis for assessing their role in regulating hormone levels and their potential as biomarkers of endocrine disruption in the Steller sea lion, 17&beta-hydroxysteroid dehydrogenase (17&beta-HSD), 3&beta-hydroxysteroid dehydrogenase/5-ene-3-ketosteroid isomerase (3&beta-HSD) and 3&alpha-hydroxysteroid dehydrogenase (3&alpha-HSD) were assayed in homogenates of placenta (n=13) as well as lung, subcutaneous fat and skin from one female and five male pups (1-4 weeks). 17&beta-HSD activity with estradiol (E2) and testosterone (T) was detected in the placenta samples as was 3&alpha-HSD activity with 5&alpha-DHT. 3&beta-HSD activity with DHEA was not detected. With regard to 17&beta-HSD activity in pup tissues, lung samples had the lowest activity and skin the highest. The ratio of 17&beta-HSD activity with E2 and T varied from 0.1 to 1.1 for skin and 0.1 to 2.3 for fat. For male pup skin samples, the 17&beta-HSD/3&alpha-HSD activity ratio varied from 0.27 to 7.2. For subcutaneous fat the range was 0.16-5.1. No 3&alpha-HSD activity was detected in the female pup skin sample. The marked variations in activity levels and ratios are consistent with the presence of multiple isoforms of 17&beta-HSD. They are also suggestive of differential regulation of 17&beta-HSD, 3&alpha-HSD and 3&beta-HSD in skin and fat, tissues in which the levels of these enzymes are known to be regulated in other species by gonadal steroids. Although the basis for the marked differences between samples remains to be clarified, our findings suggest activity patterns and ratios may be sensitive markers of endocrine status and endocrine disruption in sea lion pups.
