Characterization and distribution of extracellular matrix components and receptors in GH(3)B(6) prolactin cells

GH(3)B(6) cells, a rat pituitary tumor cell Line, synthesize and secrete la rge amounts of prolactin (PRL) in vitro. In the present work, we evaluated the capacity of these cells to express extracellular matrix (ECM) component s and receptors in vitro. The expression of laminin (LN), fibronectin (FN) and type IV collagen (CIV) was investigated by immunofluorescence assays. I n comparison to PRL distribution, where around 50-70 % of the cells contain ed PRL concentrated in the Golgi region, a variable immunolabeling for the three ECM components could be observed in the majority of GH(3)B(6) cells. Importantly, this pattern was not modified when cells were cultured in the presence of 30 nM thyroliberin (TRH). The expression of the ECM receptors: alpha5 beta1 (FN receptor), alpha6 beta1 (LN receptor) and CD44 (hyaluronic acid receptor) could be demonstrated by cytofluorometric analysis. Using b iochemical procedures, we analyzed the synthesis and secretion of glycosami noglycans (GAGs). The cells synthesized and secreted mainly heparan sulfate (75 O/o) with a minor amount of chondroitin sulfate/dermatan sulfate. In a n attempt to evaluate the individual contribution of the ECM components to influence cell morphology and PRL distribution in vitro, GH(3)B(6) cells we re cultivated separately on LN, FN and CIV substrates. Under all conditions , it was possible to observe an increase of cell adherence to the substrate , accompanied with changes of cellular morphology, characterized by the app earance of cytoplasmatic processes. However, no changes on PRL distribution could be observed. Our results suggest that endocrine tumor cell lines are involved in synthesis of ECM components and receptors. (C) 2000 Editions s cientifiques et medicales Elsevier SAS.