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(Circulation. 2005;111:1571-1573.)
© 2005 American Heart Association, Inc.

Editorial

A New "Sunshine" in the Vasculature?

Markus M. Bachschmid, PhD; Bernd van der Loo, MD

From the Department of Biology (M.M.B.), University of Konstanz, Konstanz, Germany, and the Division of Cardiology (B.v.d.L.), Cardiovascular Centre, University Hospital, Zurich, Switzerland.

Correspondence to Bernd van der Loo, MD, Division of Cardiology, Cardiovascular Centre, University Hospital Zurich, Raemistrasse 100, CH-8091 Zurich, Switzerland. E-mail bernd.vanderloo@usz.ch

Key Words: Editorials • molecular biology • vitamin D • vasculature • muscle, smooth

An extract of the first 250 words of the full text is provided, because this article has no abstract.

The discovery of vitamin D (calciol) was one of the great achievements in medicine and helped to eliminate rachitis in children and osteomalacia in adults. Vitamin D systemically acts on calcium homeostasis in parallel with parathyrin (parathyroid hormone [PTH]) and calcitonin to maintain serum calcium levels within the physiologically acceptable range. Vitamin D controls calcium and phosphate absorption in the intestine, calcium reabsorption in the kidney, and mineralization of bone.

See p 1666

Synthesis of vitamin D requires UVB irradiation of the skin, which promotes the metabolism of its precursor, 7-dehydrocholesterol, to previtamin D₃, which then slowly isomerizes to form vitamin D₃. Because exposure to sunlight is necessary for its synthesis, vitamin D has also been called the "sunshine" vitamin. Vitamin D has also been identified in archaic phytoplankton and zooplankton, where it is synthesized after solar UV exposure. Its function in these organisms is poorly understood, but it probably serves as a photosensor. This would imply an evolutionarily conserved cellular signal transduction pathway, mediating autocrine, paracrine, and endocrine signals.

Vitamin D₃ is biologically inactive and must be hydroxylated, first in the liver to 25-hydroxyvitamin D₃, and finally in the kidney by the 25-hydroxyvitamin D₃-1-hydroxylase (CYP24) enzyme system, to form the active metabolite 1,25-dihydroxyvitamin D₃ [1,25-(OH)₂D₃; calcitriol].¹ This also suggests that the term "vitamin" is possibly inappropriate, because its actions represent a classic steroidal hormone endocrine system.

Vitamin D (for simplicity, the term "vitamin D" is used to indicate its active . . . [Full Text of this Article]

Related Article:

25-Hydroxyvitamin D₃-1-Hydroxylase Is Expressed in Human Vascular Smooth Muscle Cells and Is Upregulated by Parathyroid Hormone and Estrogenic Compounds

Dalia Somjen, Yosef Weisman, Fortune Kohen, Batya Gayer, Rona Limor, Orly Sharon, Niva Jaccard, Esther Knoll, and Naftali Stern
Circulation 2005 111: 1666-1671. [Abstract] [Full Text]

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