The overall objective of this proposal is to investigate the effects of growth and hormonal controls on proteoglycan synthesis in isolated rat renal glomeruli and tubules. Proteoglycans have recently been identified as key components of the basement membrane layer of the glomeruli and tubules. Heparan sulfate is the predominant proteoglycan in the basement membrane and has been implicated to have a critical role in the maintenance of the selective permeability function of the glomerulus, where it serves as an anionic charge barrier to plasma proteins. This permeability barrier is compromised in diabetes mellitus and certain nephrotic syndromes and this alteration is a primary pathological consequence of these conditions. Renal hypertrophy is an early consequence of the diabetic state in animals and humans and may be the initiating factor in the resulting renal pathology, but virtually nothing is known about the effects of growth, and insulin and insulin-like growth factors (IGF's) on renal proteoglycan synthesis. We have recently demonstrated the presence of receptors for insulin and IGF's in glomeruli and tubules and the known anabolic effects of these hormones and particularly the implication of the IGF's as sulfation factors point to their possible involvement in the control of proteoglycan synthesis in the kidney. We are therefore proposing to compare the types and amounts of proteoglycans synthesized in vitro by renal glomeruli and tubules and to dissect the growth effects from the hormonal controls involved in this process. Two animals models will be used: (1) the uninephrectomized rat in which the remnant kidney undergoes a rapid hypertrophy and (2) the streptozotocin-diabetic rat in which early hypertrophy occurs in the absence of circulating insulin. Isolated glomeruli and tubles from normal, diabetic ard uninephrectomized animals will be incubated with 35SO4=, 3H-glucosamine and 3H-galactose with or without insulin and IGF's and the labeled proteoglycans from the cell cytoplasm, cell membrane, basement membrane and incubation medium will be isolated and characterized to define the biosynthetic process in these tissues under different growth and hormonal stimuli. Possible controls on proteoglycan synthesis such as substrate availability, protein and carbohydrate phosphorylation and level of transferase activities will also be examined. It is anticipated that these studies will provide a metabolic basis for the control of renal proteoglycan biosynthesis in growth and disease states.
