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Solar ultraviolet B radiation and photoproduction of vitamin D 3 in central and southern areas of argentina
Author(s) -
Ladizesky Marta,
Lu Zhiren,
Oliveri Beatriz,
Roman Nemesio San,
Diaz Susana,
Holick Michael F.,
Mautalen Carlos
Publication year - 1995
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1002/jbmr.5650100406
Subject(s) - vitamin d and neurology , sunlight , population , rickets , ultraviolet radiation , latitude , zoology , vitamin , incidence (geometry) , vitamin d deficiency , chemistry , biology , medicine , endocrinology , biochemistry , radiochemistry , geography , physics , environmental health , geodesy , astronomy , optics
The incidence of nutritional rickets in the southern part of Argentina is 8–12 times higher than in the rest of the country. Winter 25(OH)D serum levels in normal population of southern areas are lower than in central and northern areas. To elucidate these differences, we compared the photoconversion of provitamin D 3 (7‐DHC) to previtamin D 3 in two cities: Ushuaia (latitude 55°S) and Buenos Aires (34°S). Ampules containing 7‐DHC were exposed to sunlight one day in the middle of each month either from 10:30 a.m. to 2:30 p.m. or from 8:00 a.m. to 5:00 p.m. The percentages of photoproducts formed were determined by high performance liquid chromatography (HPLC). Previous studies have proved that this is a valid model to assess “in vitro” the photoproduction of vitamin D 3 in human skin. Previtamin D 3 + vitamin D 3 formed in Ushuaia were less ( p < 0.02) than those found in Buenos Aires during all seasons: summer, (X ± SEM) 6.4 ± 0.8% vs. 13.2 ± 1.8%; autumn, 1.2 ± 0.7% vs. 63 ± 1.3%; winter, 0.8 ± 0.7% vs. 3.6 ± 0.7%; spring, 3.4 ± 0.5% vs. 9.1 ± 1.1%. The photoproducts produced from 10:30 a.m. to 2:30 p.m. were similar for each month and latitude to those formed when the ampules were exposed from 8:00 a.m. to 5:00 p.m. We conclude that in Ushuaia there is a prolonged “vitamin D winter” during which cutaneous synthesis of vitamin D is absent, leading to lower serum values of 25(OH)D and contributing to the higher incidence of rickets.