^99mTc-Aprotinin for the Study of Renal Morphology and Tubular Function

Abstract

The kidney has an important role in the metabolism of low-molecular weight proteins, both hormonal (insulin, glucagon, growth hormone, parathyroid hormone, calcitonin) and nonhormonal (lysozyme, β₂-microglobulin interferons) (-12). Glomerular filtration and tubular reabsorption are the major renal pathways for the removal of these small proteins from the blood. Most are filtered through the glomerulus, reabsorbed at the level of the proximal tubule, and thereafter accumulated in the tubular cells where they are degraded (Figure 1). Recent evidence demonstrates that some small protein hormones, such as insulin, glucagon, growth hormone, and parathyroid hormone, also are removed from the peritubular circulation (1,3-5). A similar mechanism seems to take place also for β₂ -microglobulin (11).