Calmodulin activity in tissues of Zn- and Ca- deficient rats.

36 male Sprague-Dawley rats of an average body weight of 48 g were divided into 4 groups of 9 animals each. Group I was fed the basal diet with 63 mg/kg of Zn and 0.88% calcium, group II received a zinc-deficient diet (1.1 mg/kg of Zn), group III a calcium-deficient diet (0.0043%) and group IV a simultaneous zinc/calcium-deficient diet (1.1 mg/kg of Zn; 0.0043% calcium). All 4 groups received the diet in the same daily amounts, which was based on the food intake of the zinc-deficient group (II), in which food intake was reduced (as it also was in group IV) because of zinc deficiency. On day 28 all animals were killed and the calmodulin activity in the brain, muscles and testes was estimated. Calmodulin activity was determined by measuring the activation of a calmodulin-free phosphodiesterase against a calmodulin standard derived from porcine brain. Compared with the control animals zinc and simultaneous zinc/calcium deficiency reduced calmodulin activity in the muscles and testes, but not in the brain. Alimentary calcium deficiency did not influence calmodulin activity in the brain, muscles and testes.