In this 30-day study, the distribution and excretion, and the biological half-time (B.H.T.) of chromium in selected organs of the rat were studied and the results obtained showed a characteristic difference between hexavalent (Cr VI) and trivalent (Cr III) chromium compounds.
The rate of retention at the site of a single injection of Cr III was 88.7% (after 24 hrs) whereas that of Cr VI was 6.4%. After the administration of Cr VI, 232.73 μg or 36% of the total chromium injected was excreted into the urine within 7 days while 48.45 μg or 8.0% was excreted after Cr III administration. The amount of chromium excreted in the feces within 7 days after the injection of Cr VI was 89.17 μg or 13.9%, while the amount of chromium excreted was 146.96 μg or 24.2% of the Cr III administered.
The results of calculation of B.H.T. in several organs after a single administra-tion of Cr VI were as follows. The lung showed two components represented by two kinds of regression lines. The calculated B.H.T. was 60.2 hours (2.5 days) and 501.6 hours (20.9 days). The liver showed three components, 2.4 hours, 52.8 hours and 376.2 hours (15.7 days) ; the kidney had two components, 52.8 hours and 250.8 hours (10.5 days); the brain also showed two components, 4.4 hours and 231.52 hours (9.6 days); the heart showed two components, 66.9 hours and 334.42 hours (13.9 days) ; the testis also showed two components, 4.58 hours and 300.9 hours (12.5 days); and the blood had only one component, 334.4 hours (13.9 days).
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