A model has been designed to study lysosomal and non-lysosomal processing of insulin by hepatocytes. Attempts to delineate the non-lysosomal pathway will be made. A novel technique to assess emiocytosis of the insulin contained in MVB is to be used to determine the role of emiocytosis in insulin processing. The role of the two or more pathways in receptor recycling will also be assessed. We will examine the effect of a number of factors on processing of insulin. These factors range from a variety of energy fuels to hormones and anti-diabetic drugs. The effect of induced post-receptor defect and diabetic states will also be tested for their effect on insulin processing. A second part of the proposal involves a study of an iatrogenic cause of insulin resistance--insulin antibodies. Studies using plasmapheresis will be performed to determine the role of antibodies in the insulin resistance observed in insulin dependent diabetics. In vivo and in vitro studies will be performed to determine the effect of saturation of insulin antibodies on clearance of antibody. In addition, the role of the liver and hepatocyte Fc receptors on antibody clearance will be studied. Anti-idiotypic antibodies (antibodies to insulin antibodies) will be searched for in plasma of insulin treated diabetic patients. If present, the effect of these antibodies on in vitro systems will be studied to determine if the antibodies inhibit insulin binding to the receptor as well as exhibit insulin-like effects.