DEVELOPMENT AND VALIDATION OF IMMUNOENZYME TEST-SYSTEM FOR DETERMINATION OF 25-HYDROXYVITAMIN D IN BLOOD SERUM

Vitamin D is a general name for a group of biologically active substances, the most important of which are cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2). Chemically vitamin D belongs to secosteroids that are similar to steroid molecules except for the absence of a double bond between C9 and C10 carbon atoms in the ring B [1]. In humans, vitamin D3 is formed from 7-dyhydrocholesterol by the action of UV radiation (290–315 nm). After photobiochemical synthesis, cholecalciferol binds to vitamin D-binding protein (DBP) and is transported to the liver for further conversion to 25-hydroxyvitamin D3 (25OHD3) [2]. Cholecalciferol, through its hormonally active form — 1,25(OH)2D3 (calcitriol), has a number of different pleiotropic effects in the organism, such as the regulation of calcium homeostasis, mineralization and remodeling of bone tissue, proliferation and differentiation of various cell types as well as modulation of the immune processes. Receptors for 1,25(OH)2D3 — VDR, and all the components of the D-endocrine system (enzymes that metabolize vitamin D3), are found in various cell types. Decrease in bioavailability of vitamin D3 due to insufficient dietary intake or deterioration of its metabolism in the body is known to be a major factor in the pathogenesis of osteoporosis. In recent years, large-scale epidemiological studies have revealed a correlation between vitamin D3 deficiency and prevalence of infectious (viral infections, tuberculosis) [3–5], chronic inflammation (Crohn’s disease) [6] allergic (asthma) [7], autoimmune (multiple sclerosis, type 1 diabetes) [4, 8, 9], cardiovascular and neoplastic diseases [10–14]. The classic marker of cholecalciferol sufficiency is 25OHD level in the blood because its half-life is about 2–3 weeks and the serological samples (serum or plasma) can be stored frozen for a long period until analyzed [1]. EXPERIMENTAL ARTICLES