DETERMINATION OF VITAMIN-D, VITAMIN-A, AND VITAMIN-E IN SERA AND VITAMIN-D IN MILK FROM CAPTIVE AND FREE-RANGING POLAR BEARS (URSUS-MARITIMUS), AND 7-DEHYDROCHOLESTEROL LEVELS IN SKIN FROM CAPTIVE POLAR BEARS

The difference between serum levels from 36 captive and 56 free-rangin g polar bears (Ursus maritimus) for 25-hydroxyvitamin D (25-OH-D) was found not to be significant (mean +/- SD = 348 +/- 215 nmol/L [captive ], 360 +/- 135 nmol/L [free-ranging], t = 0.30, df = 52.8, P = 0.76), whereas the difference for retinol and alpha-tocopherol was significan t (retinol, 1.37 +/- 0.67 mu mol/L [captive] 1.89 +/- 0.63 mu mol/L [f ree-ranging], t = 3.88, df = 72.4, P <0.001, alpha-tocopherol, 18.56 /- 18.56 mu mol/L [captive], 48.76 +/- 13.92 mu mol/L [free-ranging], t = 7.85, df = 61.9, P < 0.001). Due to the high fat content in the po lar bear diet, seal blubber may be the source of these fat-soluble vit amins. Six skin biopsies were analyzed from captive polar bears at the Denver Zoological Gardens for 7-dehydrocholesterol levels and found t o contain 0.11 +/- 0.03 nmol/cm(2). This finding also helps to support the contention that the source of vitamin D for polar bears may be in gestion and not cutaneous production. Vitamin D content in the milk fr om one captive sow in the den (0.14 nmol/g) and 10 free-ranging sows w ith cubs of the year out on the ice pack (0.0042 +/- 0.0073 nmol/g) we re also evaluated. It would be helpful to evaluate additional milk sam ples from denning and non-denning sows with cubs to see whether vitami n D content varies according to the stage of lactation. (C) 1998 Wiley -Liss, Inc.