REGENERATION OF MYOEPITHELIAL CELLS IN RAT SUBMANDIBULAR GLANDS AFTERYTTRIUM ALUMINUM GARNETT LASER IRRADIATION

The regeneration of myoepithelial cells in rat submandibular salivary gland after partial irradiation with yttrium aluminium garnett (YAG) l aser was investigated. The irradiated glands were examined immunohisto chemically for actin, histochemically for alkaline phosphatase (ALP), and by transmission electron microscopy (TEM). In control glands, myoe pithelial cells were positive for actin and ALP. Electron microscopica lly, the positive reaction for actin was associated with the myofilame nts of myoepithelial cells, and the plasma membrane of myoepithelial c ells was positive for ALP. One day after YAG laser irradiation, the ir radiated region was necrotic. By 5 days, duct-like structures and epit helial clusters were observed at the interface between the necrotic zo ne and the remaining undamaged glands; immature acini appeared after 7 days. No reaction in duct-like structures or epithelial clusters to a ctin or ALP was recognizable by 5 days. However, at 7 days, actin and ALP-positive spindle cells appeared at the periphery of the duct-like structures and immature acini. After 10 days, both actin-positive and ALP-positive cells increased in number. These observations indicate th at during regeneration, actin-positive and ALP-positive cells regenera te myoepithelial cells, and it is suggested that this differentiation to myoepithelial cells is closely related to that of luminal to acinar cells. In addition, TEM observations indicate that regenerated myoepi thelial cells originated from the basal cells of duct-like structures.