Renal glomerular basement membrane. In vivo biosynthesis and turnover in normal rats

Glomerular basement membrane was labeled in vivo by the injection of tracer amounts of radioactive glycine and proline, and subsequently purified by osmotic lysis followed by sequential treatment with detergents. Analysis of tail tendons from these animals allowed comparison of basement membrane biosynthesis and degradation with these parameters in the newly synthesized fractions of fibrillar collagen. Peak radiolabeling with [3H]glycine occurred within 24 h, declining steadily thereafter in both basement membranes and salt-soluble tail tendon collagen. Calculated turnover times for [3H]glycine-labeled glomerular basement membrane and salt-soluble tail collagen were similar. Turnover of the collagenous portion of glomerular basement membrane was slightly longer, comparable to the acetic acid-soluble fraction of fibrillar collagen. Glomerular basement membrane is readily labeled after parenteral injection of radioactive precursors. Its biologic half-life is comparable to that of soluble fibrillar collagen, indicating a more rapid turnover than previously believed.