Phenotypic changes of calponin in salivary gland myoepithelial cells during postnatal development of rats

Calponin (CALP) is a 34 kDa protein which interacts with actin, tropomyosin and calmodulin, end regulates contractive roles of smooth muscle cells. Th e present study deals with the expression of CALF and actin in myoepithelia l cells (MECs) during postnatal development of rat salivary glands. In the postnatal development of MECs, the specimens obtained from submandibular (S MG) or sublingual glands (SLG) on 0 to 84 days old rats were examined by im munocytochemistry. MECs detected by CALF and actin were observed from day 0 to mature salivary glands, and the expressions of actin immunoreaction in MECs of salivary glands on days 5 or 7 were higher than those of CALP, whil e in MECs of salivary glands of rats over 5 weeks old, the expressions of C ALF were a little higher than in actin. MECs in SMGs and SLGs during the po stnatal development were characterized by existence of CALF immunoreactivit y. whereas actin immunostaining was strongly localized in the smooth muscle cells of the blood vessels. No MECs detected with CALF and actin were obse rved in ductal segments including striated ducts and granular convoluted tu bules (GCT), suggesting that the secretion from GCT cells was not related t o CALF and actin. The CALF immunoreactivity is a useful marker for MECs in salivary glands in the rat.