N-nitrosodimethylamine-induced forestomach tumours in male Sprague-Dawley rats fed a zinc-deficient diet.

Fifty-one zinc-deficient rats and 46 zinc-sufficient, pair-fed controls were administered N-nitrosodimethylamine intragastrically at a dose level of 2 mg/kg body weight, twice weekly for three weeks, followed by 4 mg/kg body weight of the same carcinogen twice weekly for another five weeks. After 45 weeks, none of the control rats had developed epithelial abnormalities in the oesophagus or forestomach or any lesion in other tissues. Oesophageal epithelial hyperkeratosis was detected in all zinc-deficient rats, but no tumour was found. Hyperkeratosis and acanthosis were found in the forestomach of 100% and 88%, respectively, of the zinc-deficient rats; 63% of the zinc-deficient rats also developed squamous papillomas in the forestomach.