Modulation of glomerular proteoglycans by insulin-like growth factor-1.
Effect of insulin-like growth factor-1 (IGF) on the synthesis of glomerular proteoglycans (PGs) in an ex vivo recirculating organ perfusion system was investigated. Kidneys were perfused with a medium (approximately 80 ml) containing [35S]-sulfate (250 microCi/ml) and IGF (62.5 to 625 ng/ml). After radiolabeling, a small cortical piece was saved for tissue autoradiography, and the remaining kidney and the perfusion medium were utilized for biochemical studies. The glomeruli were isolated; their PGs extracted and characterized. A two- to threefold increase of the total radioactivities in tissue and media fractions was observed with the exposure to IGF. By Sepharose CL-6B chromatography, the tissue PGs eluted as two peaks (A and B) with Kav = 0.24 and 0.48, and the majority of the radioactivity was confined to peak A. This peak contained intact PGs while peak B included glycosaminoglycan (GAG) chains. Elution profiles of the glomerular PGs were similar in the control and IGF groups. However, there was a disproportionate increase of chondroitin/dermatan sulfate in the IGF group. The media fractions also had two peaks, and most of the radioactivity was associated with peak B containing GAG chains. A remarkable accentuation of peak B along with significant increase in the chondroitin/dermatan sulfate were observed in the IGF group. By DEAE-Sephacel chromatography, the PGs/GAGs of IGF group eluted at a relatively lower salt concentration as compared to the control. Autoradiography revealed a relatively high concentration of radioactivity over the mesangium as compared to the other cell types of the glomerulus. [35S]-methionine studies revealed a generalized increase of protein synthesis in the IGF group, but comparatively much less than that of PGs/GAGs. These results indicate that IGF enhances the biosynthesis of PGs/GAGs by various cell types of the renal glomerulus, especially that of the mesangial cell, as reflected by the selective increase of chondroitin/dermatan sulfate.
Watanabe
Y
Y
Department of Pathology, Northwestern University Medical School, Chicago, Illinois.
Kashihara
N
N
Makino
H
H
Kanwar
Y S
YS
D000818:Animals; D001345:Autoradiography; D002809:Chondroitin Sulfates / Q000096:biosynthesis; D003871:Dermatan Sulfate / Q000096:biosynthesis; D005920:Glomerular Mesangium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007678:Kidney Glomerulus / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000378:metabolism; D010477:Perfusion; D011509:Proteoglycans / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
D011509:Proteoglycans; D003871:Dermatan Sulfate; D007334:Insulin-Like Growth Factor I; D002809:Chondroitin Sulfates; D008715:Methionine