The studies presented here are designed to; (i) examine the timing of appearance of the extracellular matrix (ECM) components, laminin, collagen IV and I and their receptors of the integrin family during rat parotid gland development; (ii) isolate and characterize the gene encoding a proline-rich protein (PRP); (iii) compare the timing of appearance of beta-adrenergic receptors (beta-AR) with the PRP gene expression during development; and (iv) investigate the role of laminin and collagen IV on the A5 cell adherence. During this reporting period we have; (1) shown that laminin B1, B2 but not A chain, collagen IV and I genes and alpha6 and beta1 integrin genes are highly expressed during the early stages (0, 7 and 14 days) of parotid gland development and decline to the adult levels at 21 days. High levels of laminin, collagen IV and beta1 integrin were localized in the basal membrane around the developing acinar and ductal cells and lower amounts at later times. This pattern of expression is concomitant with the morphological and proliferative changes occurring in these cells during development; (2) isolated four PRP related clones and characterized one of these clones, PRP 5. This PRP 5 gene contained a putative cAMP regulatory element in the 5 flanking region; (3) demonstrated that the high levels of beta-AR at 21 days of age corresponds with the high levels of the PRP mRNA at this time; (4) shown that laminin and/or collagen IV promote the early adherence of A5 cells in a focal like pattern.
