Plasma 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol concentrations are decreased in hind limb unloaded Dahl salt-sensitive female rats.
Plasma 1,25-dihydroxyvitamin D (1,25-(OH)(2)D) concentration was shown to decrease during bed rest in several studies when baseline plasma 25-hydroxyvitamin D (25-OHD) concentration was sub-optimal. Dahl salt-sensitive female (S) rats, but not Dahl salt-resistant female (R) rats, demonstrated a 50% decrease in plasma 1,25-dihydroxycholecalciferol (1,25-(OH)(2)D(3)) concentration after 28 days of hind limb unloading (HU, disuse model) during low salt intake (0.3%). We tested the vitamin D endocrine system response of female S rats to hind limb unloading during high salt intake (2%, twice that of standard rat chow to mimic salt intake in the USA). Hind limb unloading resulted in lower plasma 25-OHD(3) concentrations in S-HU rats than in R-HU rats (P<0.05) and greater urinary loss of 25-OHD(3) by S-HU rats than by S rats (P<0.05). Plasma 1,25-(OH)(2)D(3) concentration of S-HU rats was half that of S rats, but was unchanged in R-HU rats. The association of low plasma 25-OHD concentration with decrease in plasma 1,25-(OH)(2)D concentration of hind limb unloaded rats and of bed rest participants (published studies) suggests that low vitamin D status might be a risk factor for decrease in plasma vitamin D hormone concentration during long-term immobilization or bed rest.
Thierry-Palmer
Myrtle
M
Department of Biochemistry, Morehouse School of Medicine, 720 Westview Drive, SW, Atlanta, GA 30310-1495, USA. thierrm@bellsouth.net <thierrm@bellsouth.net>
Cephas
Stacy
S
D015650:24,25-Dihydroxyvitamin D 3 / Q000097:blood / Q000652:urine; D000311:Adrenal Glands / Q000033:anatomy & histology / Q000502:physiology; D000818:Animals; D001769:Blood / Q000187:drug effects; D001835:Body Weight / Q000502:physiology; D002112:Calcifediol / Q000097:blood* / Q000652:urine; D002117:Calcitriol / Q000097:blood* / Q000652:urine; D002118:Calcium / Q000097:blood / Q000652:urine; D005260:Female; D019417:Hindlimb Suspension / Q000502:physiology*; D009929:Organ Size / Q000502:physiology; D010281:Parathyroid Hormone / Q000097:blood; D011485:Protein Binding / Q000502:physiology; D011507:Proteinuria / Q000652:urine; D051381:Rats; D020303:Rats, Inbred Dahl / Q000097:blood* / Q000502:physiology; D012964:Sodium / Q000652:urine; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000494:pharmacology
D010281:Parathyroid Hormone; D017673:Sodium Chloride, Dietary; D015650:24,25-Dihydroxyvitamin D 3; D012964:Sodium; D002117:Calcitriol; D002112:Calcifediol; D002118:Calcium