Thomas M. Galligan, Lori Schwacke, Wayne E. McFee,
Blubber, a specialized form of adipose tissue in marine mammals, has been identified as a useful matrix for the assessment of steroid hormone homeostasis in cetaceans. However, blubber cortisol measurements are not quantitatively predictive of circulating cortisol concentrations in bottlenose dolphins. In other mammals, adipose tissue metabolizes steroid hormones. Thus, we propose that the disagreement between blubber and blood cortisol in bottlenose dolphins could be due in part to metabolism of corticosteroids in blubber. The purpose of this study is to characterize the ability of blubber to interconvert cortisol and cortisone using an in vitro design. We demonstrate that bottlenose dolphin blubber microsomes interconvert cortisol and cortisone, an effect that is knocked down by denaturing the microsomes, indicating this is an enzymatic process. Therefore, we conclude that blubber is likely a site of active steroid metabolism, which should be considered in future studies utilizing blubber as a matrix for endocrine assessment.
cortisol, cortisone, blubber, microsome, dolphin, marine mammal, steroid, 11-?HSD