I. Kaplan et al., The effect of desalivation on 4-nitroquinoline-1-oxide-induced tongue carcinogenesis: a morphometric study of nucleolar organizer regions, J ORAL PATH, 30(1), 2001, pp. 48-52
Saliva is an important factor in the oral cavity and could be significant i
n protecting against carcinogens. In experimental models of carcinogenesis,
saliva was shown to have a temporary protective effect against the carcino
gens DMBA and 4-nitroquinoline-oxide (4NQO). Silver-stained nucleolar organ
izer regions (AgNORs) are considered markers for both proliferative capacit
y and prognosis. The purpose of the present study was to investigate the ef
fect of desalivation on AgNOR parameters in lesions induced by the carcinog
en 4NQO in a rat model, in order to trace early nuclear changes. The study
group consisted of 120 male Wistar-derived rats. The experimental group (n=
56) underwent surgical desalivation; the control group (n=56) underwent a s
ham operation, and both groups were administered a solution of 0.001% 4NQO
in the drinking water. A normal group (n=8) did not receive surgery and dra
nk tap water. Rats were sacrificed at 7, 14, 22, and 28 weeks. Formalin fix
ed, paraffin embedded sections of the tongue were silver-stained and AgNOR
parameters were analyzed using computerized image analysis. In both desaliv
ated and control groups, the nuclear area was significantly higher than the
normal. This difference was already evident at 7 weeks. The mean AgNOR are
a was significantly higher in the desalivated group at week 7 and continued
to increase over time. The mean AgNOR number was also significantly higher
in the desalivated group at week 7. Differences between the desalivated an
d control groups diminished with time. These changes in proliferative activ
ity, as expressed by AgNOR parameters, presented earlier changes in compari
son to those observed in microscopic examination of the same slides. Result
s suggest that saliva in the oral cavity can de lay malignant transformatio
n, but continued exposure to the carcinogen overrides this effect. AgNOR st
ain seems to be sensitive and allows for early identification of intranucle
ar changes.