The present invention relates to transfected primary and secondary somatic cells of vertebrate origin, particularly mammalian origin, transfected with exogenous genetic material (DNA) which encodes erythropoietin or an insulinotropin [e.g., derivatives of glucagon-like peptide 1 (GLP-1)], methods by which primary and secondary cells are transfected to include exogenous genetic material encoding erythropoietin or an insulinotropin, methods of producing clonal cell strains or heterogenous cell strains which express erythropoietin or an insulinotropin, methods of gene therapy in which the transfected primary or secondary cells are used, and methods of producing antibodies using the transfected primary or secondary cells. The present invention also includes primary and secondary somatic cells, such as fibroblasts, keratinocytes, epithelial cells, endothelial cells, glial cells, neural cells, formed elements of the blood, muscle cells, other somatic cells, which can be cultured and somatic cell precursors, which have been transfected with exogenous DNA encoding EPO or an insulinotropin, which is stably integrated into their genomes or is expressed in the cells episomally.