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Collagen study and regulation of the de novo synthesis by IGF-I in hemocytes from the gastropod mollusc, Haliotis tuberculata.

To evidence a collagen synthesis and identify which type(s) of collagen is present in hemocytes from the mollusc Haliotis tuberculata, we have performed three separate approaches, namely, de novo synthesis by cultured cells, immunological approaches, and northern blot analysis. We demonstrated first that after 40-hr labeling, the de novo synthesis of collagen in the cell layer of cultured hemocytes represents 9.48 +/- 1.25% with respect to the total [(3)H]proline-labeled protein synthesis. In addition, IGF-I elicited a significant stimulation of collagen synthesis in cultured hemocytes in a dose-dependent manner from 10(-10) to 10(-8) M. The maximal stimulation (10(-9) M) induced an increase of 286 +/- 56% with respect to 100% control. By immunocytochemistry and immunoblotting, we showed that hemocytes present immunoreactive molecules to antibodies directed against the type I fibrillar collagen. In addition, using as a probe Hf 677 corresponding to a human pro alpha1(I) collagen cDNA and which encompasses the (Gly-X-Y) repeated sequence found in all Metazoa, four collagen transcripts of approximately 6.4, 5, 2.2, and 2 kb in length have been detected. These data suggest the presence of fibrillar type I collagen in hemocytes and are compatible with the concept that these cells are involved in the extracellular matrix deposition, a cardinal function in tissue repair as well as in developmental processes. Our model may appear as an excellent system to study the role of growth factors on the regulation of collagen synthesis by molluscan hemocytes. J. Exp. Zool. 287:275-284, 2000.