The effect of fasting on calcium content and Ca(2+)-ATPase activity in the brain tissues of 5 weeks and 50 weeks old rats was investigated. Brain calcium content and Ca(2+)-ATPase activity in the microsomal and mitochondrial functions of the brain homogenate from young and elderly rats were significantly increased by overnight-fasting. These increases were appreciably restored by a single oral administration of glucose solution (400 mg/100 g body weight) to fasted rats. In comparison with young and elderly rats, brain calcium content and microsomal Ca(2+)-ATPase activity were significantly elevated by increasing ages. The effect of ageing was not seen in the brain mitochondrial Ca(2+)-ATPase activity. When calcium (50 mg/100 g) was orally administered to young and elderly rats, brain calcium content was significantly elevated. The calcium administration-induced increase in brain calcium content was greater in elderly rats than in young rats. Also, calcium administration caused a significant increase in Ca(2+)-ATPase activity in the microsomal and mitochondrial fractions of brain homogenates from young rats. In aged rats, the microsomal Ca(2+)-ATPase activity was not further enhanced by calcium administration, although the mitochondrial enzyme activity was significantly raised. The present study demonstrates that the fasting-induced increase in brain calcium content is involved in Ca(2+)-ATPase activity raised in the brain microsomes and mitochondria of rats with different ages, supporting a energy-dependent mechanism in brain calcium accumulation.