The Effects of Calcium, Phosphorus, Magnesium, Sodium, and Zinc in Improving the Depression of Gonadal Development in Growing Male Rats Kept under a Disturbed Daily Rhythm-Investigations Based on the L16(215)-Type Orthogonal Array

Abstract

The purpose of this study 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. This experimental protocol was designed based on the L16(2(15))-type orthogonal array, which can examine six factors. Five minerals (calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), and zinc (Zn)) were selected as experimental factors, and the dietary content of these minerals was normal (AIN-76 diet) or 1/3.5 of the normal content. Lighting conditions (constant darkness or normal lighting) were also added as a factor. Four-week-old rats (Fischer 344 strain) were kept under constant darkness or normal lighting (12-h light/dark cycle) for 4 wk. After 4 wk, the gonadal weights and serum testosterone content were evaluated. The lighting condition, Ca, Mg, and Na, and the interactions between the lighting condition and Ca, and Mg and Na were observed to affect the testes weight. Among the constant darkness groups (D-groups), the highest value for testes weight was observed under the normal-Ca, normal-Mg, and normal-Na diet, and the lowest value was observed under the low-Ca, normal-Mg, and low-Na diet. Among the normal lighting groups (N-groups), the highest value for testes weight was observed under the low-Ca, normal-Mg, and normal-Na diet, and the lowest value was observed under the normal-Ca, normal-Mg, and low-Na diet. Among the D-groups, the highest value for serum testosterone was observed under the normal-Ca, normal-Mg, and low-Na diet. Among the N-groups, the highest value was observed under the low-Ca, normal-Mg, and low-Na diet. It became clear that the amount of dietary Ca necessary for the gonadal development of rats increases when rats are kept under constant darkness as a model of disturbed daily rhythm compared with the normal lighting condition.