CALCIUM METABOLISM OF THE NORMAL RHESUS MONKEY*

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Abstract
The metabolism of Ca45 was studied in 29 rhesus monkeys (26 male, 3 female) while maintained on a nutritionally adequate diet. The Ca45 was administered by intravenous injection, by gastric intubation and in the diet. Samples of blood serum, urine and feces were collected at intervals and analyzed for total Ca and Ca45 content. Samples of soft and hard tissues were taken at autopsy and analyzed for Ca45, total Ca and ash content. Serum Ca45 activity reached a maximum within 15, 60 and 200 minutes after intravenous injection, gastric intubation and ingestion in the diet, respectively. The more readily exchangeable fraction of body Ca was calculated to be 1.19 g/monkey. The accretion rate averaged 0.243 g of Ca/monkey/day. The excretions of Ca45 during 5 days following intravenous injection, gastric intubation and ingestion in the diet were, respectively: 7.6, 5.0 and 5.3% in the urine; and 3.7, 35 and 28% in the feces. The data on the appearance and disappearance rates of Ca45 in the sera, the amounts of exchangeable Ca, the amounts of Ca45 excreted in the urine and feces, and the urine: feces ratios of Ca45 excretion reported in this study of 29 monkeys are in close agreement with data previously obtained in similar studied on 65 children. They are in disagreement with data from rats and dogs. The evidence indicates that the monkey is the best substitute for the human being in studies of Ca metabolism.