TEMPORAL AND SPATIAL EXPRESSION OF LAMININ, COLLAGEN TYPE-IV AND TYPE-I AND ALPHA-6 BETA-1 INTEGRIN RECEPTOR IN THE DEVELOPING RAT PAROTID-GLAND/

We have examined the temporal expression and cellular localization of the genes and proteins for the extracellular matrix (ECM) proteins lam inin (B1, B2 and A chain), collagen types alpha1 (IV) and alpha1 (1) a nd the integrin receptor complex alpha6/beta, during parotid gland pos tnatal development. Laminin B1 and B2 isoforms and collagens alpha1 (I V) and alpha (I) mRNA steady-state levels were highest at ages 0, 7 an d 14 days after birth and declined to the adult (90 days) level at 21 days and older. Laminin A chain transcripts were not detected at any a ge. Collagen alpha1 (IV) and laminin were localized in the basal membr ane of the developing acinar and ductal cells, while collagen alpha1 ( 1) was localized in the stroma surrounding the cells. The amounts of t hese ECM components were high at the early stages of development and l ower at later times. The pattern of expression of the alpha6/beta1 int egrin genes during development was similar to those of laminin and col lagens alpha1 (IV) and alpha1 (I). Accumulations of mRNA were high at 0, 7 and 14 days after birth and lower at 21 days and older. High leve ls of beta1 integrin were localized in the developing acinar and ducta l cell membranes at early ages (7 days); lower amounts were present in the same distribution pattern at later stages of gland development. T hese data suggest that laminin B1 and B2 and collagen type alpha1 (IV) and alpha1 (I) are consistently coexpressed with the alpha6/beta1 int egrin receptor complex in the developing acinar and ductal cells durin g parotid gland postnatal development. Their expression is concomitant with the morphologic and proliferative changes occurring in these cel ls during this period.