The overall objective of this research proposal is to characterize the insulin receptors of isolated renal glomeruli and tubules. We and others have recently identified specific insulin receptors in preparations if isolated renal glomeruli and tubules. These receptors exhibited binding characteristics and specificity for insulin and its analogues which closely resembled the well-studied insulin receptors of isolated adipocytes and hepatocytes. However, despite the importance of the kidney in handling significant quantities of the body's circulating insulin levels, and the marked pathophysiology of this organ occuring as a consequence of long-standing diabetes mellitus, our knowledge of the characteristics of these receptors, the renal metabolism and functions possibly mediated or modulated by them, and their role in the uptake and degradation of circulating insulin is still rather limited. We are therefore proposing to better elucidate the characteristics and functions of these renal insulin receptors. The binding and degradation of 125I-insulin by isolated rat renal glomeruli and tubules will be characterized in terms of receptor affinities, specificity, function, relationship of degradation to binding, and regulation of receptor number and affinity in normal states and in conditions of varying hormone levels, such as diabetes mellitus and hyperinsulinism. Crosslinking of the receptors to 125I-insulin with the use of disuccinimidyl suberate will be carried out and the receptor-ligand complexes will be separated and characterized by gel electrophoresis and gel chromatography. The effects of insulin on metabolic and enzymatic processes which are known to be insulin-sensitive in well studied tissues such as the rat adipocyte will also be examined in isolated glomeruli and tubules. The effects of insulin on physiologically relevant renal processes such as 86Rb+ uptake, Na+,K+ ATPase activity and Na+ and Na+ dependent transport will also be determined. Efforts will be made to localize the binding, degradation and metabolic effects of insulin to specific glomerular cell types and to the luminal and antiluminal membranes of renal tubular cells. It is hoped that these studies will better elucidate the characteristics of binding, degradation and metabolic effects of insulin in renal glomeruli and tubules of normal and diabetic animals, and provide some insight into the basis for the renal pathophysiology of diabetes mellitus.
| Im, J H; Pillion, D J; Meezan, E (1988) Isolation and characterization of insulin receptors from rat kidney glomeruli and tubules. Biochem Biophys Res Commun 151:370-81 |
| Meezan, E; Pillion, D J; Elgavish, A (1988) Binding and degradation of 125I-insulin by isolated rat renal brush border membranes: evidence for low affinity, high capacity insulin recognition sites. J Membr Biol 105:113-29 |
| Ku, D D; Roberts, R B; Sellers, B M et al. (1987) Regression of renal hypertrophy and elevated renal Na+,K+-ATPase activity after insulin treatment in streptozotocin-diabetic rats. Endocrinology 120:2166-73 |
| Ku, D D; Sellers, B M; Meezan, E (1986) Development of renal hypertrophy and increased renal Na,K-ATPase in streptozotocin-diabetic rats. Endocrinology 119:672-9 |
