عنوان مقاله [English]
Introduction 1, 25-dihydroxycholecalciferol [1, 25 (OH)2 D3], the major biologically active metabolite of vitamin D3 is produced by two sequential hydroxylation reactions. The first hydroxylation occurred when vitamin D3 is transported to the liver, forming 25-hydroxycholecalciferol [25-(OH) D3] and the second in the kidney, by the enzyme 1-alpha-hydroxylase (VD3 1 hydroxylase) forming 1, 25 (OH)2 D3. Vitamin D3 may have a role in regulating the morphological and functional development of intestinal villus mucosa. Calcium ions have an essential role function in activation and maturation of lymphocytes. Previous studies have demonstrated that the intracellular concentration of free Ca2+ increases in several types of cells during stress. For example, acute restraint stress enhances Ca2+ mobilization in lymphocytes from mice. In addition, Ca2+ ions are essential for production of interleukin-2 by T cells (22). Withania somnifera (WS) is an annual herb and a rich source of bioactive compounds. Several pharmacological activities of the plant have been attributed to its roots. Oral administration of root extract of WS at 10, 30 and 300 mg/kg body weight for 15 days stimulated B and T cells proliferation, induced type 1 immunity, increased the activity of machrophage and levels of immunoglobulin which indicated the potent role of extract on humoral and cellular immunity. The present study aimed to evaluate the main effects and interaction of calcitriol and WS root extract in either low or adequate Ca diets on immune response and small intestinal morphology of broiler chickens.
Material and Methods Six hundred male day old Ross 308 broilers obtained from a commercial hatchery, and reared in 60 floor pens with wood shavings litter at a stocking rate of 10 birds per pen (1×1 m). Feed and water were provided ad libitum throughout the 6–wk experimental period. The experimental design was a 2×3×2 factorial comprising of two dietary concentration of Ca (negative and positive control), three concentrations of WS root extract (0, 75 and 150 mg/kg diet), two concentrations of 1, 25 (OH)2 D3 (0 and 0.5 g/kg diet). SRBC test was used to measure humoral immunity response. So, at 25 and 32 days of age chicks were injected to evaluate the primary and secondary antibody response. On d 21 and 42, one bird per replicate was killed to determine small intestinal morphology and lymphoid organ weights. Sample sections (2.5 cm in length) were taken from the middle region of the jejunum. The tissues were stained for measurement of villus length, villus width, crypth depth and thickness of muscle layer. The General Linear Models of SAS were used to analyse all the data.
Results and Discussion The results of humoral immune response showed that reduction of dietary Ca level by 30% resulted to depression of immunoglobulin M and total antibody levels. Supplementation of WS at 150 mg/kg significantly improved the level of immunoglobulin G only in primary test. Calcium ions have an essential role function in activation and maturation of lymphocytes (10). Previous studies have demonstrated that the intracellular concentration of free Ca2+ increases in several types of cells during stress. For example, acute restraint stress enhances Ca2+ mobilization in lymphocytes from mice. In addition, Ca2+ ions are essential for production of interleukin-2 by T cells. It was found that supplementation of calcitriol resulted in shorter villus length at 21 d and shorter villus width at 42 day of age, respectively. Reduction of dietary Ca level by 30% resulted to shorter crypth depth compared to positive control diet. A researcher reported that supplementation of 25-OH-D3 decreased the length and weight of small intestine. The duodenal putrescine content was enhanced in parallel with the increase in intestinal calcium absorption, suggesting that polyamines, in particular putrescine, may be involved somehow in the intestinal calcium transport mechanism. The aliphatic polyamines, putrescine, spermidine, and spermine, are considered to be essential cell constituents that play an important role in modulating cell proliferation and differentiation.
Conclusion The results of humoral immune response showed that decreasing of dietary Ca level to 30% resulted to reduction of total antibody response. The findings showed that supplementation of calcitriol did not exert beneficial effects on intestine morphology. Supplementation of WS root extract did not affect intestine characteristics.