| First Author | Duchow EG | Year | 2021 |
| Journal | Physiol Rep | Volume | 9 |
| Issue | 23 | Pages | e15138 |
| PubMed ID | 34873873 | Mgi Jnum | J:331200 |
| Mgi Id | MGI:6842181 | Doi | 10.14814/phy2.15138 |
| Citation | Duchow EG, et al. (2021) Vitamin D binding protein greatly improves bioactivity but is not essential for orally administered vitamin D. Physiol Rep 9(23):e15138 |
| abstractText | Vitamin D3 is a prohormone that is essential for calcium homeostasis. It is naturally produced in the skin by ultraviolet-B (UVB) irradiation of 7-dehydrocholesterol. In the absence of skin production, vitamin D3 can also be obtained from oral sources. However, the actual biological equivalence of naturally produced (i.e., UVB-irradiation of skin) and oral vitamin D3 has not been determined. We previously identified a unique and specific transport mechanism for skin-generated vitamin D3 which requires vitamin D binding protein (DBP); a mechanism that differs from absorption and transport of oral vitamin D3 . In the following report, we examined the impact of this difference on the biological activity of vitamin D3 . We report that UVB-generated vitamin D3 is more potent at raising serum calcium compared to oral vitamin D3 , with the total biological activity being twofold higher. By examining the excretion of radiolabeled vitamin D3 injected unbound or pre-bound by DBP, we attributed the increased activity of skin-generated vitamin D3 to a significant reduction in biliary excretion of DBP-bound vitamin D relative to unbound vitamin D. Thus, removal of vitamin D3 from the skin by the natural DBP system markedly improves biological activity compared to that given orally. |
