95H-35 rat hepatoma cells were labelled with [32P]orthophosphate and their insulin receptors isolated on wheat germ agglutinin (WGA)-agarose and anti-(insulin receptor) serum. The incubation of these cells with 10 mm-H202 for 10 min increased the phosphorylation of both the serine and tyrosine residues of the ,3 subunit of the insulin receptor. Next, insulin receptors were purified on WGA-agarose from control and H202-treated H-35 cells and the purified fractions incubated with [y-32P]ATP and Mna+. Phosphorylation of the B3 subunit of insulin receptors obtained from H202-treated cells was 150 % of that of control cells. The kinase activity of the WGA-purified receptor preparation obtained from H202-treated cells, as measured by phosphorylation of src-related synthetic peptide, was increased about 4-fold over control cells. These data suggest that in intact cell systems, H202 may increase the insulin receptor kinase activity by inducing phosphorylation of the ,3 subunit of insulin receptor.

These results showed that anti-MPO antibody activates not only neutrophils, but also GEC, indicating that anti-rmMPO IgG-induced direct activation of GEC contributes to neutrophil adhesion to GEC, thereby increasing glomerular neutrophil infiltration in initiation and progression of pauci-immune glomerulonephritis.

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In two-dimensional tryptic phosphopeptide mapping, the ,%subunit of the insulin receptor phosphorylated by 12-O-tetradecanoylphorbol-13-acetate in rat hepatoma cells (H-35) was separated into one phosphothreonine-containing peptide and several phosphoserine-containing peptides. The synthetic peptide coding residues 1327-1343 in the C-terminal region of the rat insulin receptor was phosphorylated at the threonine residue by protein kinase C in a phosphatidylserine and oleoylacetylglycerol dependent manner. Tryptic digest of this phosphopeptide migrated to the same position as the phosphothreonine containing peptide obtained from the /?-subunit in two-dimensional phosphopeptide mapping. These data suggested that Thr 1336 of the insulin receptor is the site of phosphorylation by protein kinase C in intact cells.