Anti-inositolglycan antibodies selectively block some of the actions of insulin in intact BC3H1 cells.

We have studied the mechanism of generation of insulin mediators by using specific antibodies raised against the oligosaccharide anchor of membrane proteins. These antibodies (i) block the in vitro effects of purified insulin mediators and (ii) block the insulin-induced stimulation of pyruvate dehydrogenase in intact BC3H1 myocytes but not insulin-stimulated glucose uptake, generation of diacylglycerol, or generation of insulin mediators. When added to intact cells in the presence of insulin, these antibodies induce the accumulation of insulin mediator activity in the extracellular medium. We therefore conclude that these anti-inositolglycan antibodies block some of the effects of insulin by inhibiting the uptake of specific insulin mediators generated outside the cell.