Expression of connexin 32 and 43 is developing rat submandibular salivary glands

The expression of the gap-junction proteins connexin 32 and 43 in the devel oping rat submandibular gland was determined using revel se transcription-p olymerase chain reaction and immunohistochemistry. Sprague-Dawley rats from the 17th gestational day through to the 28th postnatal day were used. Conn exin 43 gene expression was detected on the 17th gestational day, Connexin 32 gene expression was also detected on the 17th gestational day but less i ntensely, Immunolabelling for connexin 43 was also found in the developing submandibular gland from the 17th gestational day. Prenatally the most immu noreactive areas for connexin 43 were located in the periphery of terminal tubules, but some staining was discernible between the cells in terminal bu ds. In the postnatal period. reactive areas were located at both the periph ery of acinus-like structures and around the intercalated duct. This is con sistent with the known association of connexin 43 with myoepithelial cells. Connexin 32 immunostaining was first detected in the developing submandibu lar glands on the 18th day of prenatal development. Positive staining was p resent on the lateral side of the proacinar and mature acinar cells, The nu mber of immunoreactive areas per cell increased during early development fo llowed by a significant decrease perinatally. During postnatal development the density of areas again showed a pattern of increase, These results sugg est that connexin 43 is associated with growth and differentiation in the p re- and perinatal periods and also with the contractile function of myoepit hetial cells in the postnatal period of the developing submandibular gland. It is also implied that the number of connexin 32-positive areas may corre spond to an increase or decrease in the number of proacinar and mature acin ar cells, (C) 2000 Elsevier Science Ltd, All rights reserved.