IN-VITRO STUDY OF THE EFFECT OF OSMOTIC SOLUTES ON THE INTERACTIONS BETWEEN CELLS FROM THE PERITONEUM AND PERITONEAL-CAVITY

objective: To study how the presence of osmotic solutes in medium affe cts growth of the peritoneal mesothelial cells and fibroblasts and how osmotic solutes influence the production of factors regulating growth of these cells. Design: The proliferation of mesothelial cells and fi broblasts was evaluated by measuring the incorporation of 3H-thymidine into the cells. Cells were exposed to osmotic solutes; the concentrat ion of the latter in the medium was continuously lowered over the time of the experiment to simulate changes of their concentration in the d ialysate. The synthesis of factors influencing the proliferation of th e mesothelial cells or fibroblasts, by mesothelial cells or fibroblast s themselves, or by peritoneal leukocytes, was tested by the character istics of the ''conditioned'' medium. The conditioned medium was produ ced by exposing standard medium to mesothelial or fibroblasts monolaye r or to peritoneal leukocytes over 24 hours; following filtration it w as applied to growing test cells for the study of growth factors. Resu lts: The effect of osmotic solutes on the growth of mesothelial cells is less inhibitory when their concentration is gradually lowered over the time of the study, compared to previous findings with a constant c oncentration. Peritoneal leukocytes produce growth factors for mesothe lial cells and fibroblasts. Glucose and amino acids inhibit production of peritoneal leukocyte-derived growth factors for mesothelial cells, while glycerol increases synthesis of such growth factors for fibrobl asts. Mesothelial cells produce factors stimulating the proliferation of mesothelial cells and fibroblasts. In the presence of glycerol or a mino acids synthesis of mesothelium derived growth factors for fibrobl asts is augmented. Finally, fibroblasts produce factors that inhibit t he proliferation of the mesothelial cells, and this effect is potentia ted in the presence of amino acids. Conclusions: Cytotoxicity of the o smotic solutes measured by the inhibition of growth of the mesothelial cells or their increased damage is significantly reduced during in vi tro kinetic study when the concentration of these solutes is gradually lowered. Presence of osmotic solutes in the medium affects synthesis of growth factors derived from mesothelium, fibroblasts, or peritoneal leukocytes, which affect the proliferation of mesothelial cells or fi broblasts.