INSULIN STIMULATES PRODUCTION OF GLYCOCONJUGATE LAYERS ON THE CELL-SURFACE OF GASTRIC SURFACE MUCOUS CELL-LINE GSM06

The mechanism of regulation of mucus production in the gastric mucosa remains unclear. Recently, we established a gastric surface mucous cel l line GSM06, which produces periodic acid-Shiff (PAS)-positive glycoc onjugate (mucus) layers on the cell surface, from transgenic mice harb oring a temperature-sensitive simian virus 40 large T-antigen gene. In this study, GSM06 cells were examined for its production of PAS-posit ive glycoconjugate layers to acid secretagogues and growth factors. Th e cells were cultured at nonpermissive temperature (39 degrees C) for 3-18 days and stained with PAS. Insulin (1-30 mu g/ml; 0.29-8.6 mu M) time and dose-dependently increased production of glycoconjugates on t he cell surface. When glycoconjugate layers produced by stimulation of insulin (3-30 mu g/ml; 0.86-8.6 mu M) were removed from the cell surf ace of GSM06 cells by a mild trypsin treatment, PAS-positive materials were remarkably decreased (day 18). In addition, morphological findin gs indicate that a high concentration of insulin (30 mu g/ml; 8.6 mu M ) produced thick PAS-positive glycoconjugate layers just like normal g astric surface mucosa on the cell surface on day Is. In contrast, hist amine (0.1-100 mu M), carbachol (0.1-100 mu M), gastrin-17 (0.1-100 nM ), epidermal growth factor (0.01-10 ng/ml; 1.7-1,700 pM), transforming growth factor-alpha (0.01-10 ng/ml; 1.8-1,800 pM), and fetal bovine s erum (1-10%) did not increase glycoconjugate production. These finding s suggest that insulin is a stimulator of glycoconjugate production, a nd stimulates production of glycoconjugate layers on the cell surface in the gastric surface mucous cell line GSM06.