CALCIUM METABOLISM OF THE NORMAL RHESUS MONKEY*

Abstract

In research related to human nutrition, it has become a tradition first to conduct extensive stud-ies on one or more species of experimental animal, and then to attempt to confirm the findings from these studies on relatively small groups of human beings. It is important that the animal species selected for study should closely resemble the hu-man being with respect to the absorption, metabo-lism, degradation, and excretion of the nutrient under study. The species acceptable for the study of one nutrient is not necessarily the species of choice for the study of a different nutrient. The rat and the dog have been used extensively in nutrition studies. These species appear to me-tabolize many nutrients in a manner similar to that of human beings, but Wanner and co-work-ers (1) presented preliminary data indicating that neither of these species is a satisfactory substitute for human beings in studies of calcium metabo-lism. They injected trace amounts of Ca45 in-travenously, and observed that the ratio of Ca45 excretion in the urine and feces during the next 5 days was 1: 22 in the rat, 1: 10 in the dog, 2: 1 in the monkey, and 2: 1 in the human being. It has since been reported by Bronner, Harris, Maletskos and Benda (2) that the urine: feces excretion ratios of six young human subjects ranged from 0.50: 1 to 3.2: 1 and averaged 1.9: 1. To our knowledge there are no other reports of similar studies on physiologically normal human subjects. Data obtained on patients with carci-noma, multiple myeloma, and thyroid disorders indicate that the excretion of Ca45 is disturbed in these situations, for the urine: feces excretion *A portion of this paper was presented at the Fifth