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The non-carcinogenicity of 1-naphthylamine
which flare-up reactions could be consistently provoked in guinea-pigs 7 wk after patch testing. but not arter 3 months. In this species dense infiltrates of polymorphontlclear leukocytes were observed at the flare-tip sites. but rcw such leukocytes were observed in the women in the prcscnt study.]
The
non-carcinogenicity
of I-naphthylamine
Purchase. I. F. H.. Kalinowski. A. E.. Ishmael. J.. WilJ.. Gore. C. W. & Chart. 1. S. (I9SI). Lifietimc carcinogenicity study of I- and 2-nnphthyl~umine in dogs. Br. J. Corwr 44, 892. son.
No evidence of carcinogenicity was round in six dogs given I-naphthplaminc (I-NA) at an oral dose level of I5 mg/kg body weight. 5 days!wk for 9 yl (Cirrtl irt f.C.% 19SI. 19. 792). The I-NA in this GISC contained only 0.03%0,04”, 2-~laphthylaminc (2-NA). in contrast to the 3%6”,, usually present in the commcrcial material until the last decade. The findings thus suggcstcd that 2-NA contamination may have been responsible for the bladder papillomata round previously in two dogs given I -NA (Bonser PI ol. Ur. J. Co~cer 1956. 10, 533) and for the excess or bladder cancer in workers csposed to commercial I-NA (Cast YI ~1. Br. J. intl. ~\ded. 1954, Il. 75). Nevertheless. I-NA is mutagenic in bacteria arter metabolic activation. and positive results were also obtained in some yeast and in ~;irra mammalian cell assays (Elolw
crtiou u,/’ Shorr-Term
Tests ,Ji)i. Corcirroycws:
Rqm
y/
/he Inrerntrriontrl C’o//ohorotiw /+oqrr/n~. pp. 6S & 77. Edited by F. J. de Serres 6r J. Ashby. Elsevier/NorthHolland Inc.. New York. I9Sl ). The mutagenicity or I-NA after metabolic activation may be ascribed to its N-hydrosy mctabolite (iv-hydrosy-I-NA). which is itsclr directly mutagenic in bacteria (Belman <‘I I,/. C~wrr Res. 1965. 28, 535; Ci/ec/ if! F.C.7: 1966. 4. 472; McCoy ?I rrl. E~~rir. Mutrcgeu.19Sl. 3, 499). Furthermore, implantation ol stearic acid pellets containing TO”,, N-hydrosy-I-NA into the bladders or mice produced signilicantly more local tumours than did stearic acid alone (Boyland Ed I!/. Br. J. Co~wr 1964. 18. 575). I\‘-HydrosyI -NA also caused more local tumours after ip injection into rats than did the equivalent metabolitc of 2-NA (Belman (‘I trl. lot. cir.: Radomski Ed (I/. Ctrww Rex I97 I. 31, 1461). Some thmours at other sites were also round in rats treated ip with N-hydrosy-I-NA. and three bronchogcnic tumours and one hepatoma occurred in 5s mice given a single SC injection or N-hydrosy-I-NA during the 24 hr alter birth (Radomski ?I rrl. lot. cit.). Like many carcinogens. A’-hydrosyI -NA binds covalently to DNA. RNA and protein (Kadlubar ef ~1. CC~KW Rex 1978. 38, 3623). However. whereas > I2 DNA adducts/lOs nucleotides could be detected in the urothelium or two dogs given 3H-labelled 2-NA (S mg/kg body weight). none (above the detection limit or l/IO8 nucleotides) could be round after administration ir S.5 mg 3H-labcllcd I-NA/kg body weight (idem. Ctr,ci,loyr,lesi.s I9S I. 2, 467). Purchase el r,/. (cited above) now describe a study in which beagle dogs were treated orally 5 day&k \vith 400 mg lligl~ly-p~~rified l-NA, containing 0111~ 5 ppm 2-NA (group 1). I-NA to which 0.5 or 67,
2-NA had been added (groups 2 and 3 respectively) or pure 2-NA (group 4). Groups l-3, comprising rour dogs or each sex per group. were treated for up to IO9 months and survivors were killed at I25 months, while treatment of group 4 (three males and two rcmalcs) ended arter 34 months. and all of the dogs were dead by 47 months. The daily dose levels (5 days/wk) wcrc equivalent to about IS.5 mg total naphthyl~uiiine/kg [or malts and 2 l-21 mg/kg ror remales, and groups I. 2 and 3 received approximately I x lo-“. 0.1 and 1.1-1.X mg 2-NA/kg/day respectively. Groups or rour malt and rour female dogs were used as vehicle-treated controls. Transient increases in plasma Icvcls of the cnzymcs alanine trnnsaminase (ALT). alkaline phosphatasc (ALP) and ornithine carbosyl transrcrase (OCT) were seen in group I. with a more marked response in erotms 2 and 3. Grout 4 showed hieh ALT activities. with less eFTect on OCT. but ALP levels were normal. Blood urea levels were also increased in group 4 animals. Haematuria occurred in all dogs in group 4, and in one of the dogs rrom each of groups 3 and I. No treatment-related effects on body weight were round. and only in the urinary system were there gross or histopathological lesions that were considered to be treatment-related. All or the dogs in group 4 had large cauliflower-like masses involvine most of the bladder mucosa. Histological esaminat~on revealed these to be transitional-cell carcinomas. Two of the group 3 animals had solitary papillirorm masses (early carcinomas) while two or the dogs from group 2 had solitary haemangiomas arising in the submucosa and protruding into the bladder lumen. The group-l dog that had developed hnematuria showed focal cystitis with dilation of the submucosal blood vessels and associated haemorrhage. Two ol” the controls and one dog in group 3 also displayed Tocal epithelial hyperplasia or the bladder wall. Hyperplasia or the epithelium or the ureter was seen in single dogs in groups 2 and 3 and in three dogs in group 4. The only statistically signifcant difcrences in tumour incidence were seen 117 group 4. in which there were increased incidences or bladder tumours and of animals bearing malignant turnours. Larger numbers of thyroid and skin tumours were seen in groups I. 2 and 3 than in the controls. but the diflerences were not significant, It was concluded that the low incidence of bladder cancer in dogs given I-NA with 6”,, added 2-NA esplained the carcinogenicity or impure I-NA in earlier studies. The significance or haemangiomas in two or the animals given I -NA with O,S’;, adcled 2.NA (group 2) was uncertain. since similar Icsions did not appear to have been reported in previous studies. The localized vascular dilation observed in the bladder submucosa of one dog given purilicd I-NA may have represented a preangiomatous change. but could not be considered neoplastic. In view of the small size of the treatment groups. the study may not be regarded as proving conclusively the non-carcinogenicity 0r I-NA. However. it was calculated that ir the haemangiomas in group 2 were taken as evidence of the carcinogenic activity of 2-NA. the daily dose of about 0.1 mg 2-NA/kg that was required to produce them was only 0,5?b of the dose of I-NA given to group 1. I-NA can thus be considered at least 200 times less potent than 2-NA in inducing bladder cancer in dogs.
The
non-carcinogenicity
of I-naphthylamine
Purchase. I. F. H.. Kalinowski. A. E.. Ishmael. J.. WilJ.. Gore. C. W. & Chart. 1. S. (I9SI). Lifietimc carcinogenicity study of I- and 2-nnphthyl~umine in dogs. Br. J. Corwr 44, 892. son.
No evidence of carcinogenicity was round in six dogs given I-naphthplaminc (I-NA) at an oral dose level of I5 mg/kg body weight. 5 days!wk for 9 yl (Cirrtl irt f.C.% 19SI. 19. 792). The I-NA in this GISC contained only 0.03%0,04”, 2-~laphthylaminc (2-NA). in contrast to the 3%6”,, usually present in the commcrcial material until the last decade. The findings thus suggcstcd that 2-NA contamination may have been responsible for the bladder papillomata round previously in two dogs given I -NA (Bonser PI ol. Ur. J. Co~cer 1956. 10, 533) and for the excess or bladder cancer in workers csposed to commercial I-NA (Cast YI ~1. Br. J. intl. ~\ded. 1954, Il. 75). Nevertheless. I-NA is mutagenic in bacteria arter metabolic activation. and positive results were also obtained in some yeast and in ~;irra mammalian cell assays (Elolw
crtiou u,/’ Shorr-Term
Tests ,Ji)i. Corcirroycws:
Rqm
y/
/he Inrerntrriontrl C’o//ohorotiw /+oqrr/n~. pp. 6S & 77. Edited by F. J. de Serres 6r J. Ashby. Elsevier/NorthHolland Inc.. New York. I9Sl ). The mutagenicity or I-NA after metabolic activation may be ascribed to its N-hydrosy mctabolite (iv-hydrosy-I-NA). which is itsclr directly mutagenic in bacteria (Belman <‘I I,/. C~wrr Res. 1965. 28, 535; Ci/ec/ if! F.C.7: 1966. 4. 472; McCoy ?I rrl. E~~rir. Mutrcgeu.19Sl. 3, 499). Furthermore, implantation ol stearic acid pellets containing TO”,, N-hydrosy-I-NA into the bladders or mice produced signilicantly more local tumours than did stearic acid alone (Boyland Ed I!/. Br. J. Co~wr 1964. 18. 575). I\‘-HydrosyI -NA also caused more local tumours after ip injection into rats than did the equivalent metabolitc of 2-NA (Belman (‘I trl. lot. cir.: Radomski Ed (I/. Ctrww Rex I97 I. 31, 1461). Some thmours at other sites were also round in rats treated ip with N-hydrosy-I-NA. and three bronchogcnic tumours and one hepatoma occurred in 5s mice given a single SC injection or N-hydrosy-I-NA during the 24 hr alter birth (Radomski ?I rrl. lot. cit.). Like many carcinogens. A’-hydrosyI -NA binds covalently to DNA. RNA and protein (Kadlubar ef ~1. CC~KW Rex 1978. 38, 3623). However. whereas > I2 DNA adducts/lOs nucleotides could be detected in the urothelium or two dogs given 3H-labelled 2-NA (S mg/kg body weight). none (above the detection limit or l/IO8 nucleotides) could be round after administration ir S.5 mg 3H-labcllcd I-NA/kg body weight (idem. Ctr,ci,loyr,lesi.s I9S I. 2, 467). Purchase el r,/. (cited above) now describe a study in which beagle dogs were treated orally 5 day&k \vith 400 mg lligl~ly-p~~rified l-NA, containing 0111~ 5 ppm 2-NA (group 1). I-NA to which 0.5 or 67,
2-NA had been added (groups 2 and 3 respectively) or pure 2-NA (group 4). Groups l-3, comprising rour dogs or each sex per group. were treated for up to IO9 months and survivors were killed at I25 months, while treatment of group 4 (three males and two rcmalcs) ended arter 34 months. and all of the dogs were dead by 47 months. The daily dose levels (5 days/wk) wcrc equivalent to about IS.5 mg total naphthyl~uiiine/kg [or malts and 2 l-21 mg/kg ror remales, and groups I. 2 and 3 received approximately I x lo-“. 0.1 and 1.1-1.X mg 2-NA/kg/day respectively. Groups or rour malt and rour female dogs were used as vehicle-treated controls. Transient increases in plasma Icvcls of the cnzymcs alanine trnnsaminase (ALT). alkaline phosphatasc (ALP) and ornithine carbosyl transrcrase (OCT) were seen in group I. with a more marked response in erotms 2 and 3. Grout 4 showed hieh ALT activities. with less eFTect on OCT. but ALP levels were normal. Blood urea levels were also increased in group 4 animals. Haematuria occurred in all dogs in group 4, and in one of the dogs rrom each of groups 3 and I. No treatment-related effects on body weight were round. and only in the urinary system were there gross or histopathological lesions that were considered to be treatment-related. All or the dogs in group 4 had large cauliflower-like masses involvine most of the bladder mucosa. Histological esaminat~on revealed these to be transitional-cell carcinomas. Two of the group 3 animals had solitary papillirorm masses (early carcinomas) while two or the dogs from group 2 had solitary haemangiomas arising in the submucosa and protruding into the bladder lumen. The group-l dog that had developed hnematuria showed focal cystitis with dilation of the submucosal blood vessels and associated haemorrhage. Two ol” the controls and one dog in group 3 also displayed Tocal epithelial hyperplasia or the bladder wall. Hyperplasia or the epithelium or the ureter was seen in single dogs in groups 2 and 3 and in three dogs in group 4. The only statistically signifcant difcrences in tumour incidence were seen 117 group 4. in which there were increased incidences or bladder tumours and of animals bearing malignant turnours. Larger numbers of thyroid and skin tumours were seen in groups I. 2 and 3 than in the controls. but the diflerences were not significant, It was concluded that the low incidence of bladder cancer in dogs given I-NA with 6”,, added 2-NA esplained the carcinogenicity or impure I-NA in earlier studies. The significance or haemangiomas in two or the animals given I -NA with O,S’;, adcled 2.NA (group 2) was uncertain. since similar Icsions did not appear to have been reported in previous studies. The localized vascular dilation observed in the bladder submucosa of one dog given purilicd I-NA may have represented a preangiomatous change. but could not be considered neoplastic. In view of the small size of the treatment groups. the study may not be regarded as proving conclusively the non-carcinogenicity 0r I-NA. However. it was calculated that ir the haemangiomas in group 2 were taken as evidence of the carcinogenic activity of 2-NA. the daily dose of about 0.1 mg 2-NA/kg that was required to produce them was only 0,5?b of the dose of I-NA given to group 1. I-NA can thus be considered at least 200 times less potent than 2-NA in inducing bladder cancer in dogs.