COMPARATIVE RETENTION ABSORPTION OF CHROMIUM-51 (CR-51) FROM CR-51 CHLORIDE, CR-51 NICOTINATE AND CR-51 PICOLINATE IN A RAT MODEL

Recently, there has been a renewed interest in better defining the metabolism of chromium (Cr) with respect to both its absorption and cellular action. In the current study we investigated the absorption/retention of 3 Cr(III) compounds (Cr chloride [CrCl], Cr nicotinate [CrNic], Cr picolinate [CrPic]) over a 12 h period in a rat model. Male rats (150 - 170 g) were gavaged with 44 muCi (2.7 nmoles) Cr-51 as CrCl3 x 6 H2O, CrNic or CrPic. Rats were killed at 1, 3, 6, and 12 h post-gavage. Cardiac blood was collected and liver, kidneys, pancreas, testes, and gastrocnemius were removed, weighted and assayed for Cr-51. The amount of Cr-51 in these tissues, along with that in urine (collected for the 6 and 12 h groups), was used to calculate Cr-51 absorbed/retained. Urine, followed by muscle and blood, had the highest percent of absorbed/retained counts. For the majority of the time points and tissues, the average percent Cr-51 retained was higher in CrNic-gavaged rats than in CrCl- or CrPic-gavaged rats. Tissues collected 1 h post-gavage from CrNic rats had retention percentages that were 3.2 to 8.4- fold higher than in the CrPic or CrCl groups. Three h post-gavage, CrNic rats had blood, muscle, and pancreatic Cr-51 retentions that were 2.4 to 8 times higher than CrPic-gavaged rats. By 6 and 12 h post-gavage, the ''absorbed/retined'' tissues were 1.8 to 3.8 times higher in CrNic than in CrPic rats. It is evident from the above that when investigating the absorption/retention of Cr, it is critical to evaluate urinary Cr-51 activity, which reflects absorbed Cr, and early time points. The results show that there can be significant differences in the bioavailability of different Cr compounds.