The purpose of the present study is to evaluate the modulatory role of either vitamin D or coconut oil or both together on the thyroid parafollicular cells (C cells), by using immunohistochemistry (IHC) as well as total calcium (Ca) levels of diabetic adult male mice (Mus musculus) induced by streptozotocin (STZ).The mice were divided into 7 equal groups (10 mice/each). The duration of the experiment was 4 weeks. Gp.I: normal control mice group without any treatments. Gp.II & Gp.III: non-diabetic mice groups received vitamin D orally in a daily dose of 6.25 ml/kg b.w/d or coconut oil at dose of 7.5 ml /kg b.w/d. for 4 weeks, respectively. Gp.IV: diabetic mice group injected i.p. with a single dose of STZ dissolved in saline solution in a dose of 200 mg/kg b.w to induce diabetes. Gps.V, VI & VII: diabetic mice groups administered orally with vitamin D or coconut oil or both together at the same previous doses. The results recorded non-significant changes in the blood glucose, insulin and total Ca levels of non-diabetic mice groups. A high significant increase in blood glucose level and a significant decrease in insulin and total Ca values of diabetic mice group were recorded as compared to the normal control ones. Diabetic mice group received vitamin D only recorded significant increase in blood glucose level and non-significant decrease in insulin and total Ca levels as compared to the normal control group; while the diabetic mice received coconut oil alone or co-administered with vitamin D recorded non-significant increase in blood glucose levels and a non-significant decrease in insulin and total Ca values as compared to control group. IHC observations in the thyroid glands of normal control or non-diabetic mice received either vitamin D or coconut oil expressed normal moderate to strong immunoreactivity to C cells adjacent to the follicular cells at the basement membrane. The diabetic mice expressed intense immunoreactivity to C cells than those in normal control ones. The diabetic mice given vitamin D or coconut oil expressed moderate to strong immunoreactivity to C cells, while those given both vitamin D and coconut oil together expressed an obvious recovery of immunostain to C cells and they displayed approximately similar to the control normal ones. In conclusion, the present results indicated that both vitamin D and coconut oil together play an important role in the modulation and recovery of the thyroid C cells of diabetic mice as well as the total Ca values, and restored these cells to normal form more than those taken either vitamin D or coconut oil alone.
Key words: Hyperglycemia, Glucose, Insulin, Calcium, Thyroid gland, Immunohistochemistry, Image analysis, Mice.