Optical and ultrastructural pathology of vitamin A pretreated hamster cheek pouch--exposed to lime (Ca(OH)2) and tobacco over total life span.

A close correlation is postulated between tobacco chewing and the high incidence of oral cancer and precancer in many South East Asian nations. However, attempts to induce malignancy in laboratory animals by exposure to ingredients of betel quid are unsuccessful. This is another attempt to induce malignancy in the hamster cheek pouch epithelium by exposure to the ingredients of betel quid - lime and tobacco, for the total life span of the animals - 100 to 110 weeks. Parallel conditioning by exposure to vitamin A is also included. The cheek pouch epithelium of animals exposed to the test substances for total life span shows only epithelial dysplasia of a marked degree, but no evidence of malignancy. It is concluded that it is not possible to simulate the time-dose relationship in human addiction to tobacco or to betel chew in experimental animals due to their comparatively small life span.