The effects of nutrients in improving the depression of gonadal development in growing male rats kept under disturbed daily rhythm--investigations based on the L8(2(7)) type orthogonal array--.

The purpose of this experiment was to clarify the effects of nutrients on the gonadal development of male rats kept under constant darkness as a model of disturbed daily rhythm. Protein, methionine, vitamins, minerals and fat were selected as experimental factors, and eight kinds of diets were prepared based on the L8(2(7)) type orthogonal array. Dietary contents of the nutrients were normal (AIN-76 diet) or 1/3 to 1/2 of the normal content. Four-week-old rats (Fischer 344 strain) were kept under constant darkness for 4 wk. Control groups were kept under 12-h light/dark cycle. After 4 wk, the gonadal weights and serum testosterone content were evaluated. The effects of nutrients on gonadal development in rats differed between constant darkness groups (D-groups) and normal lighting groups (N-groups). Among the D-groups, the highest value for testes weight was observed under the normal protein, methionine added, low vitamin, low mineral and normal fat diet. The lowest value for testes weight was observed under the low protein, methionine added, normal vitamin, normal mineral and low fat diet. Among the N-groups, the highest value for testes weight was observed under the normal protein and no methionine diet, and the lowest value was observed under the low protein and no methionine diet. Among the D-groups, the highest value for serum testosterone was observed under the normal protein and low mineral diet. In the N-groups, serum testosterone was not affected by nutritional factors. It became clear that the amounts of protein, methionine, vitamins, minerals, and oil which are necessary for the gonadal development of growing male rats change when kept in constant darkness.