抄録
In rats, it has been reported that nutritional factors have important effects on the development of spontaneous proliferative lesions in the adrenal medulla, and it is known that administration of sugar alcohols such as xylitol and vitamin D<SUB>3</SUB> results in tumor production in the adrenal medulla. The action mechanism has not been clarified, but it is suggested that calcium plays an important role, reacting with stress due to hypercalcemia and increasing catecholamine synthesis. In our study, F344 rats (10 males/stage/group) were fed two types of diet (commercially-available basal rodent diet — calcium: 1.00%, vitamin D<SUB>3</SUB>: 130 IU/100g; and modified high calcium and vitamin D3 diet — calcium: 1.50%, vitamin D<SUB>3</SUB>: 700 IU/100g), and plasma calcium, the amount of calcium and catecholamine metabolites excreted into urine measured periodically. The animals were necropsied in week 13 or 26 of administration, subjected to histopathological examination of the adrenal, and subjected to image analysis by immunohistochemical staining with PCNA to confirm proliferative changes in the adrenal medulla. In the results, the modified high calcium and vitamin D<SUB>3</SUB> diet feeding group showed the following changes: increased excretion of calcium into urine throughout the study period; a slight increase in the excretion of catecholamine metabolites into urine; and an increased number of PCNA positive cells per unit area in the medulla area. No remarkable differences in body weight, food consumption or plasma calcium were recorded between the modified high calcium and vitamin D<SUB>3</SUB> diet feeding group and the normal diet group. Based on these results, it became clear that the high calcium and vitamin D<SUB>3</SUB> diet promoted proliferation of adrenal medulla and increased catecholamine synthesis through the increase in calcium metabolism in rats.
