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EDTA and the rat intestine
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The chemical environment& Fd Coamrt. 7hBicol. Vol. 17. no. 5
Three patients (group l), two of whom had undergone only brief periods of exposure (0.25 and 1.75 yr), showed a normal or slightly decreased formation of sperm, and the germ cells and Sertoli cells showed no distinct abnormalities. The two patients in group 2 had long histories of DBCP exposure (at least 10 yr) and had no spermatogenic activity. Microscopy revealed that there were no germ cells in the seminiferous tubules and there was no evidence of cellular necrosis or residual bodies either in the lumina of the seminiferous tubules or within the cytoplasm of the Sertoli cells. The third group consisted of five patients subjected to DBCP exposure for periods between these two extremes. These patients had reduced sperm counts, and spermatogenic cells were seen only in a minority of the seminiferous tubules. In the three more severely affected men in this group, spermatogenic activity was limited to a few short segments of the tubules. The Sertoli cells of the group-3 men were well preserved and appeared similar to those in group 2. Although the limited number of patients prevented any statistical treatment of the data, the severity of reduction in spermatogenic activity correlated with the duration of exposure to DBCP. The mechanism of DBCP’s action on the testis is unknown. Was the suppression of spermatogenesis due to a failure of the normal process responsible for the removal of spermatogonia at the stem-cell level? The histological findings in this study provide some support for this possibility. On the other hand DBCP could be acting primarily on the stem cells, which because of their position are more readily accessible to chemicals circulating in the blood than are the Sertoli cells. The latter are major components of the blood-testis barrier, providing a protected compartment within which the germ cells complete their division and differentiation. The authors consider that critical analysis of a laboratory model is essential for the further assessment of the effects of DBCP.
EDTA and the rat intestine Rosenblatt, D. E. & Aronson. A. L. (1978). Calcium _ ethylenediaminetetraacetate (CaEDTA) toxicity: timeand dose-response studies on intestinal DNA synthesis in the rat. Exp/ ml. Path. 28, 202. Rosenblatt, D. E., Doyle, D. G. & Aronson, A. L. (1978). Calcium ethylenediaminetetraacetate (CaEDTA) toxicity: time- and dose-response studies on intestinal morphology in the rat. Expl mol. Path. 28, 215. ethylenediaminetetraacetate Calcium disodium (CaNa,EDTA) is used in small amounts as a food additive and is poorly absorbed from the gut (Joint FAO/WHO Expert Committee on Food Additives, F.A.O. Nutr. Mtg Rep. Ser. No. 4OA,B,C; WHO/ Food Add./67.29, p. 44). Injections of the salt have been used to treat lead poisoning in man and domestic animals, but they have also been shown to produce
ultrastructural changes in the kidneys and morphological changes in the intestines of rats (Cited in F.C.T. 1978, 16, 81). The first study cited above shows the relationship between continuous iv infusion of CaNazEDTA and the inhibition of intestinal DNA synthesis. In doseresponse studies, rats were given an iv infusion over 24 hr of 0.75, 1.5, 3 or 6 mmol CaNa,EDTA/kg/24 hr, and in time-response studies they were given an infusion of 6 mmol CaNa,EDTA/kg/24 hr for 6, 12, 18 or 24 hr. In each group an ip injection of [Me-‘4C]thymidine (0.25 mCi/kg body weight) was given 1 hr before the animals were killed and its incorporation into intestinal DNA was determined. Significant inhibition of DNA synthesis occurred after infusion of 3 mmol CaNa,EDTA/kg/24 hr. After a 24-hr infusion of 6 mmol/kg/24 hr, CaNa,EDTA inhibited DNA synthesis to a degree similar to that recorded 2 hr after an iv injection of cytosine arabinoside, a potent inhibitor of DNA synthesis. An iv injection of 25 mg folate/kg had no effect on CaNa,EDTA-induced inhibition of DNA synthesis, despite previous indications (Taylor & Jones, Biochem. Pharmac. 1978, 21, 3313) that folate might protect against this effect of CaNa,EDTA. When zinc- or cobalt-containing EDTA chelates (6 mmol/kg/24 hr) were administered for 24 hr. no inhibition of DNA synthesis occurred. Recovery of the ability of the intestine to synthesize DNA in rats dosed with 6 mmol CaNa* EDTA/kg/24 hr was enhanced by Zn supplementation but not by Co or Mn supplementation (acetate salts of the metals given iv ; 12 pmol/rat). The second study cited describes changes in intestinal morphology when rats were dosed with CaNazEDTA as in the dose- and time-response experiments described above. A dose of 6 mmol/kg/ 24 hr infused over 24 hr was needed for marked morphological changes to occur-the villi were shortened, with a shortened epithelium and narrowed brush borders. The crypt epithelium was more cuboidal and contained basophilic bodies. There were increases in the numbers of lymphoid cells, particularly in the lamina propia, and of large mononuclear cells (possibly macrophages), but the number of plasma cells was lower than in the controls. The mitotic index was decreased. After a 36-hr infusion at 6 mmol CaNa*EDTA/kg/24 hr, the villi were reduced to low humps with little or no brush border and no mitotic figures. The epithelium was cuboidal and absent in some places; epithelial cells contained clear vacuoles possibly caused by swollen organelles such as mitochondria. The overall effect was a general reduction in the number of cells specifically differentiated into villus, goblet and Paneth cells and an increase in the number of cells normally associated with an inflammatory response. When infusion was stopped after 36 hr the intestine began to recover and after a 48-hr recovery period the mitotic index was greater than in the controls. The pattern of changes indicated the inhibition of DNA synthesis by the chelating agent, in conjunction with an inflammatory re-’ sponse.
The chemical environment& Fd Coamrt. 7hBicol. Vol. 17. no. 5
Three patients (group l), two of whom had undergone only brief periods of exposure (0.25 and 1.75 yr), showed a normal or slightly decreased formation of sperm, and the germ cells and Sertoli cells showed no distinct abnormalities. The two patients in group 2 had long histories of DBCP exposure (at least 10 yr) and had no spermatogenic activity. Microscopy revealed that there were no germ cells in the seminiferous tubules and there was no evidence of cellular necrosis or residual bodies either in the lumina of the seminiferous tubules or within the cytoplasm of the Sertoli cells. The third group consisted of five patients subjected to DBCP exposure for periods between these two extremes. These patients had reduced sperm counts, and spermatogenic cells were seen only in a minority of the seminiferous tubules. In the three more severely affected men in this group, spermatogenic activity was limited to a few short segments of the tubules. The Sertoli cells of the group-3 men were well preserved and appeared similar to those in group 2. Although the limited number of patients prevented any statistical treatment of the data, the severity of reduction in spermatogenic activity correlated with the duration of exposure to DBCP. The mechanism of DBCP’s action on the testis is unknown. Was the suppression of spermatogenesis due to a failure of the normal process responsible for the removal of spermatogonia at the stem-cell level? The histological findings in this study provide some support for this possibility. On the other hand DBCP could be acting primarily on the stem cells, which because of their position are more readily accessible to chemicals circulating in the blood than are the Sertoli cells. The latter are major components of the blood-testis barrier, providing a protected compartment within which the germ cells complete their division and differentiation. The authors consider that critical analysis of a laboratory model is essential for the further assessment of the effects of DBCP.
EDTA and the rat intestine Rosenblatt, D. E. & Aronson. A. L. (1978). Calcium _ ethylenediaminetetraacetate (CaEDTA) toxicity: timeand dose-response studies on intestinal DNA synthesis in the rat. Exp/ ml. Path. 28, 202. Rosenblatt, D. E., Doyle, D. G. & Aronson, A. L. (1978). Calcium ethylenediaminetetraacetate (CaEDTA) toxicity: time- and dose-response studies on intestinal morphology in the rat. Expl mol. Path. 28, 215. ethylenediaminetetraacetate Calcium disodium (CaNa,EDTA) is used in small amounts as a food additive and is poorly absorbed from the gut (Joint FAO/WHO Expert Committee on Food Additives, F.A.O. Nutr. Mtg Rep. Ser. No. 4OA,B,C; WHO/ Food Add./67.29, p. 44). Injections of the salt have been used to treat lead poisoning in man and domestic animals, but they have also been shown to produce
ultrastructural changes in the kidneys and morphological changes in the intestines of rats (Cited in F.C.T. 1978, 16, 81). The first study cited above shows the relationship between continuous iv infusion of CaNazEDTA and the inhibition of intestinal DNA synthesis. In doseresponse studies, rats were given an iv infusion over 24 hr of 0.75, 1.5, 3 or 6 mmol CaNa,EDTA/kg/24 hr, and in time-response studies they were given an infusion of 6 mmol CaNa,EDTA/kg/24 hr for 6, 12, 18 or 24 hr. In each group an ip injection of [Me-‘4C]thymidine (0.25 mCi/kg body weight) was given 1 hr before the animals were killed and its incorporation into intestinal DNA was determined. Significant inhibition of DNA synthesis occurred after infusion of 3 mmol CaNa,EDTA/kg/24 hr. After a 24-hr infusion of 6 mmol/kg/24 hr, CaNa,EDTA inhibited DNA synthesis to a degree similar to that recorded 2 hr after an iv injection of cytosine arabinoside, a potent inhibitor of DNA synthesis. An iv injection of 25 mg folate/kg had no effect on CaNa,EDTA-induced inhibition of DNA synthesis, despite previous indications (Taylor & Jones, Biochem. Pharmac. 1978, 21, 3313) that folate might protect against this effect of CaNa,EDTA. When zinc- or cobalt-containing EDTA chelates (6 mmol/kg/24 hr) were administered for 24 hr. no inhibition of DNA synthesis occurred. Recovery of the ability of the intestine to synthesize DNA in rats dosed with 6 mmol CaNa* EDTA/kg/24 hr was enhanced by Zn supplementation but not by Co or Mn supplementation (acetate salts of the metals given iv ; 12 pmol/rat). The second study cited describes changes in intestinal morphology when rats were dosed with CaNazEDTA as in the dose- and time-response experiments described above. A dose of 6 mmol/kg/ 24 hr infused over 24 hr was needed for marked morphological changes to occur-the villi were shortened, with a shortened epithelium and narrowed brush borders. The crypt epithelium was more cuboidal and contained basophilic bodies. There were increases in the numbers of lymphoid cells, particularly in the lamina propia, and of large mononuclear cells (possibly macrophages), but the number of plasma cells was lower than in the controls. The mitotic index was decreased. After a 36-hr infusion at 6 mmol CaNa*EDTA/kg/24 hr, the villi were reduced to low humps with little or no brush border and no mitotic figures. The epithelium was cuboidal and absent in some places; epithelial cells contained clear vacuoles possibly caused by swollen organelles such as mitochondria. The overall effect was a general reduction in the number of cells specifically differentiated into villus, goblet and Paneth cells and an increase in the number of cells normally associated with an inflammatory response. When infusion was stopped after 36 hr the intestine began to recover and after a 48-hr recovery period the mitotic index was greater than in the controls. The pattern of changes indicated the inhibition of DNA synthesis by the chelating agent, in conjunction with an inflammatory re-’ sponse.