A contrivance of rat metabolism cage for mineral balance study and the results of a few preliminary experiments using it.

The authors have contrived a rat metabolism cage with a simple structure, which is made entirely of glassware to avoid mineral contamination. It is also labor-saving in preventing mutual contamination of urine and feces, because urine and feces drop into their respective beakers immediately after they are excreted. Thus there is no need to remove the feces every four or five hours, as is the case when filter paper is used for separate collection of urine and feces. Instead, , it can be left alone during an entire collection period of 5-7 days.A few experiments were conducted using this metabolism cage to observe the excretory pathways of copper when this element is fed to rats in varying amounts or in five different compounds.In Experiment 1, the basal ration, fed to two rats, was supplemented with O-4, 000μg/head/day of copper as copper sulphate, when it primarily supplied 188μg/head/day of copper. Samples of urine and feces were collected on the last four days of every seven-day period. The results showed that most of the copper ingested was excreted in feces, and that urine copper levels did not vary greatly when copper supplement increased. It indicated that urine and feces were separated quite satisfactorily even when the amount of copper excreted in feces in a day was more than two hundred times as much as that in urine. Copper retention in rat body increased according to the increased copper intake.In Experiment 2, ten rats were divided into five lots and fed basal ration, which supplied 34μg/day of copper, supplemented with 30μg/day of copper in five different inorganic com-pounds rotationally at 10 days' periods. The samples of urine and feces were collected during the last five days of the ten-day periods. There were no significant differences in the amounts of copper excreted in urine or feces, or those retained in the body, according to the different forms of copper.The amounts of urinary copper excretion observed in Experiment 2 were significantly (P<0.01) smaller than those in Experiment 1. It seems that there is a marginal dietary copper level under which its urinary excretion decreases. As for retention, the amount of copper for maintaining the equilibrium between intake and output seems to exist between 200 and 600μg/day for a rat of 300g body weight.