Abstract
Glomeruli were isolated from rat renal cortex and incubated with radioactive lysine to study in vitro collagen synthesis in these preparations. Glomerular basement membrane was obtained by sonication, and the appearance of [ 14C]lysine and hydroxylysine in medium, membrane and intracellular proteins was determined. Total glomerular incorporation of [ 14C]lysine into protein linearly increased for up to 2 h of incubation, as did hydroxy[ 14C]lysine synthesis. The amount of [ 14C]lysine and hydroxylysine in basement-membrane protein progressively increased over a 2-h period, and membrane hydroxylysine content gradually rose during this time. Hydroxy[ 14C]lysine was recovered in the 105 000 × g pellet, reaching a hydroxylysine content of 22% in this intracellular fraction after 90 min of incubation. 60% of the protein secreted into the medium, and about 75% of newly synthesized sonicated basement membrane was acetic acid soluble. Hydroxylysine content was 33% in the acetic acid-insoluble fraction of sonicated membrane, suggesting that basement-membrane collagen was a significant component of total collagen synthesized by these preparation. The ability of isolated glomeruli to synthesize and secrete basement-membrane protein will be useful for studies concerning control of glomerular collagen and basement-membrane synthesis.
Published Version
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