Absorption, excretion and retention of 51Cr from labelled Cr-(III)-picolinate in rats

The bioavailability of chromium from Cr-picolinate (CrPic(3)) and Cr-chloride (CrCl3) was studied in rats using Cr-51-labelled compounds and whole-body-counting. The intestinal absorption of Cr was twice as high from CrPic(3) (1.16% vs 0.55%) than from CrCl3, however most of the absorbed Cr-51 from CrPic(3) was excreted into the urine within 24 h. After i.v. or i.p. injection, the whole-body retention curves fitted well to a multiexponential function, demonstrating that plasma chromium is in equilibrium with three pools. For CrPic(3), a large pool exists with a very rapid exchange (T (1/2) = < 0.5 days), suggesting that CrPic(3) is absorbed as intact molecule, from which the main part is directly excreted by the kidney before degradation of the chromium complex in the liver can occur. CrCl3 is less well absorbed but the rapid exchange pool is much smaller, resulting in even higher Cr concentrations in tissue such as muscle and fat. However, 1-3 days after application, the relative distribution of Cr-51 from both compounds was similar in all tissues studied, indicating that both compounds contribute to the same storage pool. In summary, the bioavailability of CrPic(3) in rats is not superior compared to CrCl3.