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Role in the regulation of immune function and autoimmune disorder prevention.Regulation of calcium metabolism in muscle.Regulation of calcium uptake by the bone tissue.Regulation of calcium absorption in the gut.Generation of vitamin D3 and its involvement in calcium metabolism

Synthesis of1, 25(OH)2 vitamin D3 It has been shown recently that human macrophages treated with a mycobacterium lipoprotein showedincreasedexpression of 25OH D-1alpha hydroxylase and vitamin D receptor as well as the induction of cathelicidin (a class of antimicrobial peptides called defensins) in response to 25(OH) vitamin D3. The pigment can be a limiting factor in the photo- isomerization reaction because melanin can also absorb UVB radiation.

Following a moderate exposure to sunlight UVB rays trigger the synthesis of melanin by the melanocytes in the lower strata of epidermis.

Under normal circumstances some 25-50 micrograms of 7-dehydrocholesterol/cm2 of skin are available for vitamin D3 synthesis. Generation of pre-vitamin D3 depends on the intensity and wavelength of UV radiation. UVB rays are most effective in a narrow range, between 295-300 nm.

UVB radiation causes the photo-isomerization of 7-dehydrocholesterol in the plasma membrane of stratum spinosum and stratum basale cells of the epidermal layer of the skin.

A bulge appears in one of the strands and as a result DNA replication is impaired.

After 72 hours massive skin peeling off takes place.ĭamage to DNA strands caused by UVB radiation UVB can damage DNA directly by causing the formation of a cyclobutane thymine dimer involving two adjacent thymine bases.Inflammatory cells (lymphocytes, macrophages) move to the interstitial space.An inflammatory response is triggered – synthesis of cytokines, prostaglandins, heat shock proteins.Initial redness and swelling – dilation of blood capillaries in the dermis.The most deadly form – malignant melanoma is mostly caused by indirect DNA damage, through oxidative stress due to reactive oxygen species. The mechanism of sunburns An overexposure to UV radiation (typical summer day) can cause sunburn and in the long run some form of skin cancer. UV rays and their biological action on skin cells UVB causes sunburns (longer exposure) UVA produces tanning without burning. Oh, thou life giving celestial body, welcome to the new day – Anonymous The Sunshine Vitamin in Health and Disease © BioSoft Publishing 2009