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Immunoreactive somatomedin B in urine
The Journal of Clinical Endocrinology and Metabolism
|September 1, 1975
Summary
Normal adults excrete significant amounts of immunoreactive somatomedin B in urine. Most somatomedin B found in urine is free, unlike in plasma where it is protein-bound.
Area of Science:
- Endocrinology
- Urology
- Biochemistry
Background:
- Somatomedin B (Sm-B) is a growth factor with poorly understood excretion pathways.
- Understanding Sm-B's renal handling is crucial for metabolic and endocrine research.
Purpose of the Study:
- To quantify urinary excretion of immunoreactive somatomedin B in healthy adults.
- To determine the proportion of free versus bound somatomedin B in urine and plasma.
Main Methods:
- Collected urine samples from 8 normal adults over a 4-hour period.
- Measured plasma concentrations of somatomedin B concurrently.
- Assessed the free and protein-bound fractions of somatomedin B in both urine and plasma.
Main Results:
- Mean urinary excretion of immunoreactive somatomedin B was 27.6 +/- 4.4 mug over 4 hours.
- Mean plasma concentration was 5.9 +/- 0.9 mug/ml.
- Free somatomedin B constituted 85.9% of urinary Sm-B, while plasma Sm-B was predominantly bound (<5% free).
Conclusions:
- Healthy adults exhibit substantial urinary excretion of immunoreactive somatomedin B.
- Urinary somatomedin B is primarily in a free, unbound form, contrasting with its bound state in plasma.
- These findings suggest a distinct renal handling mechanism for somatomedin B compared to its systemic circulation form.