title: Ineffective vitamin D synthesis in cats is reversed by an inhibitor of 7-dehydrocholestrol-delta7-reductase.
abstract: Changes in plasma 25-hydroxyvitamin D (25-OHD) were used as an index of vitamin D status of cats. Plasma 25-OHD concentration of kittens given a purified vitamin D-free diet and exposed to direct summer sun for 15 h/wk declined at a similar rate as kittens given the same diet kept indoors. Similarly, plasma 25-OHD of kittens exposed to ultraviolet (UV) lamps declined at a similar rate as kittens not exposed, and these kittens developed clinical signs of vitamin D deficiency. Eight weaned kittens were given the vitamin D-free purified diet until their plasma concentrations of 25-OHD were < 5 nmol/L. They then had the hair on their backs clipped at weekly intervals and were paired on the basis of skin color and exposed to UV light for 2 h/d. One member of each pair was given an inhibitor of 7-dehydrocholesterol (5, 7-cholestradien-3beta-ol)-delta7-reductase (EC 1.3.1.21) in the diet. Cats receiving the inhibitor had a progressive increase in 25-OHD concentration of plasma with time to 91 +/- 22 nmol/L (mean +/- SEM), whereas cats not receiving the inhibitor had plasma 25-OHD concentrations that were not detectable (P < 0.001). Biopsy samples of skin from cats receiving the inhibitor had more than five times the concentration of 7-dehydrocholesterol (P < 0.001) than the skin of control cats. Low concentration of 7-dehydrocholesterol (presumably due to high activity of the reductase) in the skin of cats is the major impediment to effective vitamin D synthesis. Analysis of wild caught potential prey of cats indicated that these animals could supply adequate vitamin D to meet the requirement of growing kittens.
authors: Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
authors: J G
authors: JG
authors: Morris
mesh_terms: D015652:25-Hydroxyvitamin D 2 / Q000097:blood*; D000818:Animals; D001717:Birds; D002415:Cats; D004032:Diet; D008297:Male; D051379:Mice; D010088:Oxidoreductases / Q000032:analysis / Q000037:antagonists & inhibitors*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D051381:Rats; D012867:Skin / Q000737:chemistry; D013472:Sunlight; D014466:Ultraviolet Rays; D014807:Vitamin D / Q000032:analysis / Q000096:biosynthesis*
chemical_list: D014807:Vitamin D; D015652:25-Hydroxyvitamin D 2; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C019995:7-dehydrocholesterol reductase