Evidence for stress steroid metabolism by marine mammal blubber

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. Blubber microsomes were collected by differential centrifugation and were treated with cortisol or cortisone and appropriate cofactor. Conversion of cortisol to cortisone (and vice versa) was measured by liquid-chromatography tandem mass spectrometry. This dataset contains measured values of cortisol and cortisone from these experiments.