IN-VITRO EFFECTS OF METHIONINE-ENKEPHALIN, SOMATOSTATIN AND INSULIN ON CULTURED GONADAL CELLS OF THE SNAIL HELIX-ASPERSA

Isolated snail gonadal cells were cultured in the presence of syntheti c neuropeptides in order to determine the subsequent effect of these s ubstances on gonadal synthetic activities. Gonadal cells were incubate d for 24 h in concentrations of methionine-enkephalin, somatostatin an d insulin ranging from 10(-4) M to 10(-9) M, in medium 199 supplemente d with 6% Ultroser G. Synthesis of DNA and protein by the cultured cel ls were simultaneously estimated by measuring incorporation of H-3 thy midine and S-35 methionine. The rate of labelled precursor incorporati on was measured using the liquid scintillation technique. All substanc es tested exerted a dose-dependent effect. The synthetic activity of t he cultured cells was highest when the concentration of the peptides a dded to the medium approximated the physiological levels. Methionine-e nkephalin, somatostatin and insulin at 2 x 10(-8) M significantly incr eased H-3 thymidine incorporation, by 62%, 69% and 69% respectively, a nd protein synthesis by 42%, 57% and 57%, respectively. In the case of juvenile gonadal cultured cells, a similar increase in H-3 and S-35 i ncorporation was registered for a 10(-7) M peptide concentration. Both lower and higher peptide concentrations inhibited H-3 thymidine and S -35 methionine incorporation. Pharmacological studies suggest the exis tence of methionine-enkephalin and somatostatin-like receptors on snai l gonadal cells. These results indicate that our gonadal cell culture model provides a useful tool for the study of the neuroendocrinologica l control of the activity of snail gonadal cells.