CARCINOGENIC NITROSAMINES IN CANTONESE SALT-DRIED FISH
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1032 CARCINOGENIC NITROSAMINES IN CANTONESE SALT-DRIED FISH Y. Y. FONG E. O’F. WALSH. Department of Biochemistry, University of Hong Kong, Hong Kong. SIR,-Since the discovery by Magee and Barnes that dimethylnitrosamine is carcinogenic} other carcinogenic nitrosamines have been described.2,3 It appears that the N-nitrosamines include some of the most potent carcino- gens known: they are organ-specific and have been shown selectively to induce malignant tumours in liver,1.4-6 lung,’ nasal sinus,9 aesophagus,1O bladder," kidney,7,12 fore-stomach,13,14 and ovary 9 in various animal species. Druckrey et al. have demonstrated that some nitrosamines are capable of inducing cancer by a single dose. At the suggestion of Dr. H. C. Ho, of the Hong Kong Medical and Health Department Institute of Radiology, we have analysed samples of Cantonese salt-fish for nitros- amines. Salt-dried fish is a common item of food among Chinese, and it was thought that carcinogenic nitrosamines, if present, might be a cause of a nasopharyngeal carcinoma to which the Cantonese appear to be especially prone. We have found both dimethylnitrosamine and diethyl- nitrosamine in all samples that we have examined of nine species of locally purchased salt-dried fish. The nitrosamines were extracted and identified by thin- layer chromatography following the method of Sen et al.,15 with slight modifications. Confirmation and quantitative determinations were achieved by gas-liquid chromato- graphy, operational conditions according to Sen et al.,15 again with slight modifications. The peaks from the fish- extracts were identical with those of added markers which had been freshly prepared from A.R. dimethylamine and diethylamine. Various salt-dried anchovies, croakers, yellow croakers, and white herrings were analysed and were found to contain 0-6-9-0 p.p.m. of dimethylnitros- amine and 1-2-21-0 p.p.m. of diethylnitrosamine. These results are corrected for a recovery of 70% which we experimentally determined. Others have found nitrosamines. in herring meal pre- served with sodium nitrite 16,17 and in smoked nitrite- treated fish.18,19 The crude salt used in the preparation of Cantonese salt-dried fish does not contain nitrite in detectable quantity, however. It appears to be crude sea-salt, for it is rich in iodide, and it contains small amounts of nitrate. The fish are not gutted and cleaned but are placed in the crude salt as soon as they are caught, a practice in marked contrast to that of British, Canadian, and American fishermen who clean their fish as soon as 1. Magee, P. N., Barnes, J. M. Br. J. Cancer, 1956, 10, 114. 2. Druckrey, H., Preussmann, R., Ivankovic, S., Schmahl, D. Z. Krebsforsch. 1967, 69, 103. 3. Magee, P. N., Barnes, J. M. Adv. Cancer Res. 1967, 10, 163. 4. Barnes, J. M., Magee, P. N. Br. J. ind. Med. 1954, 11, 167. 5. Druckrey, H., Preussmann, R., Schmahl, D., Muller, M. Natur- wissenschaften, 1961, 48, 134. 6. Druckrey, H., Steinhoff, D. ibid. 1961, 49, 487. 7. Zak, F. G., Holzner, J. H., Singer, E. J., Popper, H. Cancer Res. 1960, 20, 96. 8. Druckrey, H., Preussmann, R. Naturwissenschaften, 1962, 49, 111. 9. Druckrey, H., Steinhoff, D., Preussmann, R., Ivankovic, S. Z. Krebsforsch. 1964, 66, 1. 10. Druckrey, H., Preussmann, R., Blum, G., Ivankovic, S. Naturwis- senschaften, 1963, 50, 100. 11. Druckrey, H., Preussmann, R., Schmahl, D., Muller, M. ibid. 1962, 49, 19. 12. Magee, P. N., Barnes, J. M. J. Path. Bact. 1962, 84, 19. 13. Druckrey, H., Preussmann, R., Schmahl, D., Muller, M. Naturwis- senschaften, 1961, 48, 165. 14. Schoenthal, R., Magee, P. N. Br. J. Cancer, 1962, 16, 92. 15. Sen, N. P., Smith, D. C., Schwinghamer, L., Marleau, J. J. J. Assn. off. analyt. Chemists, 1969, 52, 47. 16. Sakshaug, J., Sognen, E., Hansen, M. A., Koppang, N. Nature, 1965, 206, 1261. 17. Ender, F., Havre, G., Helgebostad, A., Koppang, N., Madsen, R., Ceh, L. Naturwissenschaften, 1964, 51, 637. 18. Fazio, T., Damico, J. N., Howard, J. W., White, R. H., Watts, J. O. J. agric. Fd. Chem. 1971, 19, 250. 19. Sen, N. P., Smith, D. C., Schwinghamer, L., Howsam, B. J. Inst. Can. Technol. Aliment. 1970, 3, 66. they are caught. 10 It therefore seemed likely to us that nitrate-reducing bacteria were involved, and this we have confirmed. We have obtained viable cultures on salt-agar of nitrate- reducing halobacteria and salt-tolerant Staphylococcus aureus from all the samples of fish that we have examined. Further investigation is in progress. LIVER DISEASE IN CARRIERS OF Au ANTIGEN V. REINICKE E. DYBKJAER. Medical Department B and Blood Bank, Bispebjerg Hospital, Copenhagen, Denmark. SIR,-Dr. Singleton and his colleagues (Oct. 9, p. 785) report that " a substantial proportion, perhaps the majority, of Au-antigen-positive blood-donors will have liver disease ". Their evidence for this conclusion does not appear very firm, since they state that of 47 Au-antigen- positive donors found only 25 were examined, and only 10 (22%) had a histological liver examination. Biochemical data may suggest liver disease, but can never be absolute proof. Further difficulties are met with when a correlation is sought between biochemical data and the specific diagnosis of the suspected liver disease. Dr. Singleton and his colleagues mention a group of 10 donors, classified as having " subclinical hepatitis ", who had no clinical symptoms but a moderately increased bromsulphthalein-retention and moderately raised trans- aminase levels. We find the term subclinical hepatitis unjustified for a group of patients with these characteristics, which can be seen in non-hepatic diseases as well as a wide variety of liver disorders such as steatosis, cirrhosis, and hxmochromatosis. In our consecutive series of Au-antigen-positive Danish donors, 6 out of 24 donors (25%) had a perfectly normal liver-biopsy specimen. 6 (25%) further donors showed a single drop of fat in some lobules, and these 6 should probably also be considered as normal. Histological evidence of acute hepatitis was not encountered in any case. Details will be reported soon. Dr. Singleton and his colleagues state that " the null incidence of hepatitis among antigen-positive Danish donors is unexplained"." 21 However, in our group of antigen-positive donors no drug addicts were found, whereas 8 of the 25 antigen-positive donors described by Dr. Singleton and his colleagues were drug users. Thus a striking difference exists between the Copenhagen and the Denver material regarding donors with an especially high hepatitis risk. This may well explain the different incidence of acute and chronic hepatitis in the two series. H.A.A. IN PRIMARY LIVER-CELL CARCINOMA SIR,—There is growing interest in the role of hepatitis- associated antigen (H.A.A.) in the pathogenesis of primary liver-cell carcinoma.22 We have for some time been testing for H.A.A. in this disease, and now have the results in 11 patients. In 9 the diagnosis was confirmed histologically (6 by biopsy, 3 by necropsy) and in 2 it was made on clinical grounds (including positive tests for alpha-fetoprotein, using antiserum kindly provided by Dr. J. A. Smith, University College Hospital, Ibadan). Tests for H.A.A. 20. MacCarthy, J. P., Tausz, J. Salt Fish Industry in Hong Kong; p. 6. Government Printer, Hong Kong, 1952. 21. Banke, O., Dybkjaer, E., Nordenfelt, E., Reinicke, V. Lancet, 1971, i, 860. 22. Sutnick, A. T., London, W. T., Blumberg, B. S. Ann. intern. Med. 1971, 74, 442.
Transcript of CARCINOGENIC NITROSAMINES IN CANTONESE SALT-DRIED FISH
1032
CARCINOGENIC NITROSAMINES INCANTONESE SALT-DRIED FISH
Y. Y. FONGE. O’F. WALSH.
Department of Biochemistry,University of Hong Kong,
Hong Kong.
SIR,-Since the discovery by Magee and Barnes thatdimethylnitrosamine is carcinogenic} other carcinogenicnitrosamines have been described.2,3 It appears that theN-nitrosamines include some of the most potent carcino-gens known: they are organ-specific and have been shownselectively to induce malignant tumours in liver,1.4-6lung,’ nasal sinus,9 aesophagus,1O bladder," kidney,7,12fore-stomach,13,14 and ovary 9 in various animal species.Druckrey et al. have demonstrated that some nitrosaminesare capable of inducing cancer by a single dose.At the suggestion of Dr. H. C. Ho, of the Hong Kong
Medical and Health Department Institute of Radiology,we have analysed samples of Cantonese salt-fish for nitros-amines. Salt-dried fish is a common item of food amongChinese, and it was thought that carcinogenic nitrosamines,if present, might be a cause of a nasopharyngeal carcinomato which the Cantonese appear to be especially prone.We have found both dimethylnitrosamine and diethyl-nitrosamine in all samples that we have examined of ninespecies of locally purchased salt-dried fish.The nitrosamines were extracted and identified by thin-
layer chromatography following the method of Sen et al.,15with slight modifications. Confirmation and quantitativedeterminations were achieved by gas-liquid chromato-graphy, operational conditions according to Sen et al.,15again with slight modifications. The peaks from the fish-extracts were identical with those of added markers whichhad been freshly prepared from A.R. dimethylamine anddiethylamine. Various salt-dried anchovies, croakers,yellow croakers, and white herrings were analysed andwere found to contain 0-6-9-0 p.p.m. of dimethylnitros-amine and 1-2-21-0 p.p.m. of diethylnitrosamine. Theseresults are corrected for a recovery of 70% which weexperimentally determined.
Others have found nitrosamines. in herring meal pre-served with sodium nitrite 16,17 and in smoked nitrite-treated fish.18,19 The crude salt used in the preparationof Cantonese salt-dried fish does not contain nitrite indetectable quantity, however. It appears to be crudesea-salt, for it is rich in iodide, and it contains smallamounts of nitrate. The fish are not gutted and cleanedbut are placed in the crude salt as soon as they are caught,a practice in marked contrast to that of British, Canadian,and American fishermen who clean their fish as soon as
1. Magee, P. N., Barnes, J. M. Br. J. Cancer, 1956, 10, 114.2. Druckrey, H., Preussmann, R., Ivankovic, S., Schmahl, D. Z.
Krebsforsch. 1967, 69, 103.3. Magee, P. N., Barnes, J. M. Adv. Cancer Res. 1967, 10, 163.4. Barnes, J. M., Magee, P. N. Br. J. ind. Med. 1954, 11, 167.5. Druckrey, H., Preussmann, R., Schmahl, D., Muller, M. Natur-
wissenschaften, 1961, 48, 134.6. Druckrey, H., Steinhoff, D. ibid. 1961, 49, 487.7. Zak, F. G., Holzner, J. H., Singer, E. J., Popper, H. Cancer Res.
1960, 20, 96.8. Druckrey, H., Preussmann, R. Naturwissenschaften, 1962, 49, 111.9. Druckrey, H., Steinhoff, D., Preussmann, R., Ivankovic, S. Z.
Krebsforsch. 1964, 66, 1.10. Druckrey, H., Preussmann, R., Blum, G., Ivankovic, S. Naturwis-
senschaften, 1963, 50, 100.11. Druckrey, H., Preussmann, R., Schmahl, D., Muller, M. ibid. 1962,
49, 19.12. Magee, P. N., Barnes, J. M. J. Path. Bact. 1962, 84, 19.13. Druckrey, H., Preussmann, R., Schmahl, D., Muller, M. Naturwis-
senschaften, 1961, 48, 165.14. Schoenthal, R., Magee, P. N. Br. J. Cancer, 1962, 16, 92.15. Sen, N. P., Smith, D. C., Schwinghamer, L., Marleau, J. J. J. Assn.
off. analyt. Chemists, 1969, 52, 47.16. Sakshaug, J., Sognen, E., Hansen, M. A., Koppang, N. Nature,
1965, 206, 1261.17. Ender, F., Havre, G., Helgebostad, A., Koppang, N., Madsen, R.,
Ceh, L. Naturwissenschaften, 1964, 51, 637.18. Fazio, T., Damico, J. N., Howard, J. W., White, R. H., Watts, J. O.
J. agric. Fd. Chem. 1971, 19, 250.19. Sen, N. P., Smith, D. C., Schwinghamer, L., Howsam, B. J. Inst.
Can. Technol. Aliment. 1970, 3, 66.
they are caught. 10 It therefore seemed likely to us thatnitrate-reducing bacteria were involved, and this we haveconfirmed.We have obtained viable cultures on salt-agar of nitrate-
reducing halobacteria and salt-tolerant Staphylococcusaureus from all the samples of fish that we have examined.Further investigation is in progress.
LIVER DISEASE IN CARRIERS OF Au ANTIGEN
V. REINICKEE. DYBKJAER.
Medical Department B and Blood Bank,Bispebjerg Hospital,
Copenhagen, Denmark.
SIR,-Dr. Singleton and his colleagues (Oct. 9, p. 785)report that
" a substantial proportion, perhaps the majority,
of Au-antigen-positive blood-donors will have liverdisease ". Their evidence for this conclusion does not
appear very firm, since they state that of 47 Au-antigen-positive donors found only 25 were examined, and only 10(22%) had a histological liver examination.
Biochemical data may suggest liver disease, but can
never be absolute proof. Further difficulties are met withwhen a correlation is sought between biochemical dataand the specific diagnosis of the suspected liver disease.Dr. Singleton and his colleagues mention a group of 10donors, classified as having " subclinical hepatitis ", whohad no clinical symptoms but a moderately increasedbromsulphthalein-retention and moderately raised trans-aminase levels. We find the term subclinical hepatitisunjustified for a group of patients with these characteristics,which can be seen in non-hepatic diseases as well as a widevariety of liver disorders such as steatosis, cirrhosis, andhxmochromatosis.
In our consecutive series of Au-antigen-positive Danishdonors, 6 out of 24 donors (25%) had a perfectly normalliver-biopsy specimen. 6 (25%) further donors showed asingle drop of fat in some lobules, and these 6 shouldprobably also be considered as normal. Histologicalevidence of acute hepatitis was not encountered in anycase. Details will be reported soon. Dr. Singleton and hiscolleagues state that " the null incidence of hepatitisamong antigen-positive Danish donors is unexplained"." 21
However, in our group of antigen-positive donors no drugaddicts were found, whereas 8 of the 25 antigen-positivedonors described by Dr. Singleton and his colleagues weredrug users. Thus a striking difference exists between theCopenhagen and the Denver material regarding donorswith an especially high hepatitis risk. This may well
explain the different incidence of acute and chronichepatitis in the two series.
H.A.A. IN PRIMARY LIVER-CELL CARCINOMA
SIR,—There is growing interest in the role of hepatitis-associated antigen (H.A.A.) in the pathogenesis of primaryliver-cell carcinoma.22 We have for some time been testingfor H.A.A. in this disease, and now have the results in 11patients. In 9 the diagnosis was confirmed histologically(6 by biopsy, 3 by necropsy) and in 2 it was made on clinicalgrounds (including positive tests for alpha-fetoprotein,using antiserum kindly provided by Dr. J. A. Smith,University College Hospital, Ibadan). Tests for H.A.A.
20. MacCarthy, J. P., Tausz, J. Salt Fish Industry in Hong Kong;p. 6. Government Printer, Hong Kong, 1952.
21. Banke, O., Dybkjaer, E., Nordenfelt, E., Reinicke, V. Lancet, 1971,i, 860.
22. Sutnick, A. T., London, W. T., Blumberg, B. S. Ann. intern. Med.1971, 74, 442.
