Steroid hormones in multiple tissues of East Greenland polar bears (Ursus maritimus)

Abstract

The polar bear (Ursus maritimus) is threatened by climate changes and also from persistent organic pollutants affecting polar bear endocrinology governing growth and reproduction. To provide further insight into basic polar bear endocrinology, we determined the levels of steroids in multiple tissues and plasma from East Greenland polar bears. Tissue samples from 10 polar bears, 5 males (2 adults, 3 juveniles) and 5 females (all juveniles) were obtained from the Inuit hunt in Scoresby Sound during springtime. Eleven steroids: pregnenolone, 17-hydroxypregnenolone, progesterone, 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, testosterone, dihydrotestosterone, estrone, 17a-estradiol and 17b-estradiol were determined in brain, adrenal cortex, testis, testicular vein, plasma, and ovary using GC-MS/MS. In brain tissue, the neuroactive progestagen pregnenolone (11.9 ± 4.4 ng/g ww) and dehydroepiandrosterone (2.26 ± 0.43 ng/g ww) were found in high concentrations. Very high levels of testosterone and androstenedione were observed in testes ([100 ng/g ww) and plasma from testicular vein (testosterone: 108 ± 41 ng/ml; androstenedione: 35.2 ± 11.1 ng/ml). Additionally, a strong correlation was found between the levels of steroids in testes and testicular vein plasma. Progestagens were found in very high levels in ovaries from juvenile females ([100 ng/g ww). Finally, our study indicates that polar bears synthesize androstenedione via the D-4 pathway. The present study adds new insight to our knowledge on polar bear endocrinology, which may be used in future studies on polar bear ecology and studies on some of the threats from pollution and climate changes that these animals are facing.

Biomonitoring of Polycyclic Aromatic Hydrocarbon Deposition in Greenland Using Historical Moss Herbarium Specimens Shows a Decrease in Pollution During the 20th Century

“…They usually enter the food web through the consumption of phytoplankton by organisms at lower trophic levels, which are then consumed by larger marine biota, accumulating POPs in their fatty tissues and increasing in concentration at each step of the trophic chain (Corsolini et al, 2016). These compounds are therefore detectable in the tissues of many high trophic-level predators of the Arctic marine ecosystem, such as the Greenland polar bear (Ursus maritimus Phipps) and the Greenland sleeper shark (Somniosus microcephalus Bloch & J. G. Schneider) (Corsolini et al, 2016;Styrishave et al, 2017). Much higher levels of POP contamination have also been found in humans living in the Arctic regions compared with people living in other regions, which is due to a largely marine based diet.…”

A method for determination of one hundred endogenous steroids in human serum by gas chromatography-tandem mass spectrometry.

“…The authors from research group headed by Man-Ho Choi (Molecular Recognition Research Center of Korea Institute of Science and Technology) published a series of extensive metabolomic studies on the GC-MS platform, which were focused on the role of urinary steroids in human physiology and pathophysiology (Ha et al 2009, Choi and Chung 2014, Kim et al 2013, Moon et al 2016). There are few GC-MS/MS studies focused on circulating steroids in humans and other mammals, and all have quantified a limited number of steroids (Courant et al 2010, Hansen et al 2011, Matysik and Schmitz 2015, Nilsson et al 2015, Styrishave et al 2017.…”