Comparative retention/absorption of ⁵¹chromium (⁵¹Cr) from ⁵¹Cr chloride, ⁵¹Cr nicotinate and ⁵¹Cr 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 μCi (2.7 nmoles) ⁵¹Cr as CrCl₃ x 6H₂O, 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, weighed and assayed for ⁵¹Cr. The amount of ⁵¹Cr in these tissues, along with that in urine (collected for the 6 and 12 h groups), was used to calculate ⁵¹Cr 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 ⁵¹Cr 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 ⁵¹C tentions that were 2.4 to 8 times higher than CrPic-gavaged rats. By 6 and 12 h post-gavage, the 'absorbed/retained' 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 ⁵¹Cr activity, which reflects absorbed Cr, and early time points. The results show that there can be significant differences in the bioavailabillty of different Cr compounds.