- Email: [email protected]
1442. Intestinal absorption of chromium
THE CHEMICALENVIRONMENT
831
Tricresyl phosphate (TCP) and triphenyl phosphate (TPP) are both used as plasticizers (Cited in F.C.T. 1964, 2, 755). Although sensitivity to these triaryl phosphates is relatively rare, it can be a considerable problem when it does occur, as exemplified by a recent case report (Pegum, cited above). A woman with severe eczema gave a strongly positive reaction to the PVC-containing surgical tape used in applying the patch tests, as well as her spectacle frames made from cellulose acetate (CA), and the reaction was shown to be due to sensitivity to both TCP and TPP. She also reacted to a variety of household articles made from PVC and CA. Following cessation of exposure to as many of the offending products as possible (the PVC floor tiles and chairs remained), her dermatitis improved considerably but some lichenified eczema still persisted. A biochemical study on tri-o-cresylphosphate (o-TCP) is reported by Seward et aL (cited above). When o-TCP was fed to rats receiving a diet free from essential fatty acids (EFA), signs of EFA deficiency developed more quickly and increased in severity. Thus dietary levels of 0.05 or 0.1 ~o o-TCP were found to accelerate the appearance and severity of dermal lesions, to accentuate alterations in liver lipids (a rise in total lipids, in cholesterol and in the ratio of trienoic to tetraenoic fatty acids) and to cause a further depression of oxidative phosphorylation in liver mitochondria, o-TCP also depressed growth in both EFA-deficient and control rats and altered the above FA ratio in the livers of control animals, o-TCP has been reported to increase the requirement for vitamin E (Hove, Am. J. clin. Nutr. 1955, 3, 328) and to cause vitamin A deficiency in rats (Hands et al. Biochem. J. 1965, 94, 279), although the latter effect was not noted in the present investigation. These effects, as well as the accentuation of EFA deficiency demonstrated in the present study, are probably all related to the known ability of o-TCP to oxidize unsaturated lipids.
THE CHEMICAL ENVIRONMENT 1442. Intestinal absorption of chromium Donaldson, R. M. & Berreras, R. F. (1966). Intestinal absorption of trace quantities of chromium. J. Lab. clin. Med. 68, 484. Ingested chromium (Cr) is known to be poorly absorbed, being largely eliminated in the faeces (Cited in F.C.T. 1963, 1, 301; ibid 1966, 4, 540). Little is known about the relative absorption of the trivalent (Cr m) and hexavalent (Cr vr) forms, although red blood cells have been shown in vitro to take up Cr vt readily but not Cr m. A study has therefore been conducted of the intestinal absorption of trace amounts of 51Cr-labelled Cr trichloride or sodium chromate in human subjects and rats. When given orally to man or rats, both forms were excreted virtually quantitatively in the faeces. When introduced directly into the small intestine, absorption of Cr ux was still almost negligible but about 50 ~o of Cr vx was absorbed (as judged by the faecal excretion of 51Cr) and as much as 10 ~o of the dose was recovered in the urine. In vitro experiments with everted rat-intestinal preparations also showed that Cr vx was absorbed very much more readily than Cr ux. In addition, patients with achlorhydria or pernicious anaemia were found to absorb considerably more orally-administered 51Crvx than normal subjects, suggesting that acid gastric juice may inhibit intestinal absorption of Cr va. This possibility receives further support from the finding that treatment of Cr vx with acid gastric juice inhibited its subsequent absorption following introduction into the duodenum and also reduced in vitro uptake of Cr by the everted intestine. This is attributable mainly to the reduction of Cr vx to the poorly absorbed Cr m, but in addition a small proportion of the Cr v~ was absorbed on to macromolecular components of the gastric juice. It is concluded that oral ingestion of Cr w may be hazardous in achlorhydric subjects or in those in whom gastric contents are neutralized at the time of Cr vx ingestion, o
831
Tricresyl phosphate (TCP) and triphenyl phosphate (TPP) are both used as plasticizers (Cited in F.C.T. 1964, 2, 755). Although sensitivity to these triaryl phosphates is relatively rare, it can be a considerable problem when it does occur, as exemplified by a recent case report (Pegum, cited above). A woman with severe eczema gave a strongly positive reaction to the PVC-containing surgical tape used in applying the patch tests, as well as her spectacle frames made from cellulose acetate (CA), and the reaction was shown to be due to sensitivity to both TCP and TPP. She also reacted to a variety of household articles made from PVC and CA. Following cessation of exposure to as many of the offending products as possible (the PVC floor tiles and chairs remained), her dermatitis improved considerably but some lichenified eczema still persisted. A biochemical study on tri-o-cresylphosphate (o-TCP) is reported by Seward et aL (cited above). When o-TCP was fed to rats receiving a diet free from essential fatty acids (EFA), signs of EFA deficiency developed more quickly and increased in severity. Thus dietary levels of 0.05 or 0.1 ~o o-TCP were found to accelerate the appearance and severity of dermal lesions, to accentuate alterations in liver lipids (a rise in total lipids, in cholesterol and in the ratio of trienoic to tetraenoic fatty acids) and to cause a further depression of oxidative phosphorylation in liver mitochondria, o-TCP also depressed growth in both EFA-deficient and control rats and altered the above FA ratio in the livers of control animals, o-TCP has been reported to increase the requirement for vitamin E (Hove, Am. J. clin. Nutr. 1955, 3, 328) and to cause vitamin A deficiency in rats (Hands et al. Biochem. J. 1965, 94, 279), although the latter effect was not noted in the present investigation. These effects, as well as the accentuation of EFA deficiency demonstrated in the present study, are probably all related to the known ability of o-TCP to oxidize unsaturated lipids.
THE CHEMICAL ENVIRONMENT 1442. Intestinal absorption of chromium Donaldson, R. M. & Berreras, R. F. (1966). Intestinal absorption of trace quantities of chromium. J. Lab. clin. Med. 68, 484. Ingested chromium (Cr) is known to be poorly absorbed, being largely eliminated in the faeces (Cited in F.C.T. 1963, 1, 301; ibid 1966, 4, 540). Little is known about the relative absorption of the trivalent (Cr m) and hexavalent (Cr vr) forms, although red blood cells have been shown in vitro to take up Cr vt readily but not Cr m. A study has therefore been conducted of the intestinal absorption of trace amounts of 51Cr-labelled Cr trichloride or sodium chromate in human subjects and rats. When given orally to man or rats, both forms were excreted virtually quantitatively in the faeces. When introduced directly into the small intestine, absorption of Cr ux was still almost negligible but about 50 ~o of Cr vx was absorbed (as judged by the faecal excretion of 51Cr) and as much as 10 ~o of the dose was recovered in the urine. In vitro experiments with everted rat-intestinal preparations also showed that Cr vx was absorbed very much more readily than Cr ux. In addition, patients with achlorhydria or pernicious anaemia were found to absorb considerably more orally-administered 51Crvx than normal subjects, suggesting that acid gastric juice may inhibit intestinal absorption of Cr va. This possibility receives further support from the finding that treatment of Cr vx with acid gastric juice inhibited its subsequent absorption following introduction into the duodenum and also reduced in vitro uptake of Cr by the everted intestine. This is attributable mainly to the reduction of Cr vx to the poorly absorbed Cr m, but in addition a small proportion of the Cr v~ was absorbed on to macromolecular components of the gastric juice. It is concluded that oral ingestion of Cr w may be hazardous in achlorhydric subjects or in those in whom gastric contents are neutralized at the time of Cr vx ingestion, o