EFFECTS OF VERTEBRATE GROWTH-FACTORS ON DIGESTIVE GLAND-CELLS FROM THE MOLLUSK PECTEN-MAXIMUS L - AN IN-VITRO STUDY

In relation with the digestive cycle, the digestive gland cells of biv alve molluscs undergo a sequence of cytological changes which is contr olled by external and internal effecters such as putative gastrointest inal hormones and growth differentiation factors. A tissue dissociatio n method was developed to investigate the in vitro effect of the verte brate growth and differentiation factors: insulin, insulin growth fact or I (IGF-I), basic fibroblast growth factor (bFGF) and epidermal grow th factor (EGF) on the digestive gland cells of the scallop Pecten max imus. All these vertebrate peptides induced a dose-dependent increased incorporation of H-3-leucine and C-14-uridine in whole digestive glan d cell suspensions. However, after Percoll density gradient purificati on of the digestive cells, only stem and undifferentiated enriched cel l fractions were responsive to the different peptides. In addition, in sulin and ICE-I, but not EGF and bFGF, stimulated H-3-leucine incorpor ation in control dispersed mantle edge cells. These results suggest th at insulin-related peptides could work as general growth promoting fac tors in molluscs. On the other hand, EGF and bFGF, or at least their m olluscan counterparts, may be efficient growth differentiation factors in the regenerative processes occurring in the digestive gland of mol luscs.