Are myoepithelial cells responsible for the widespread expression of inducible nitric oxide synthase in pleomorphic adenoma? An immunohistochemical study
Pa. Brennan et al., Are myoepithelial cells responsible for the widespread expression of inducible nitric oxide synthase in pleomorphic adenoma? An immunohistochemical study, J ORAL PATH, 29(6), 2000, pp. 279-283
Many of the actions of nitric oxide (NO) are still poorly understood. Recen
tly, it has been shown that the inducible isoform of the enzyme nitric oxid
e synthase, iNOS, is expressed in both salivary ducts and pleomorphic adeno
ma. The current immunohistochemistry study determined whether or not this d
istribution correlated with smooth muscle actin (SMA) expression, thereby s
uggesting the expression by myoepithelial cells in both sites. Twenty cases
of histologically confirmed pleomorphic adenoma, the sections of which con
tained adjacent normal salivary gland tissue, were stained for iNOS and smo
oth muscle actin (clone 1A4). The salivary ducts of all cases were stained
intensely by both antibodies, with smooth muscle actin staining also being
noted around acini in the normal gland parenchyma. Moderate or heavy staini
ng for iNOS was found in all specimens of pleomorphic adenoma, with smooth
muscle actin being distributed in a similar manner in 19 cases. Smooth musc
le actin, but not iNOS, was also noted in blood vessels of both normal glan
ds and tumours. The correlation between iNOS and SMA in pleomorphic adenoma
was significant (P<0.001). The presence of iNOS in normal salivary ducts a
nd pleomorphic adenoma is most likely due to expression by myoepithelial ce
lls.