Origin of urinary fibronectin.

Abstract

The fibronectin fragments normally found in urine originate from the kidney and are not derived from plasma. Since these fragments are already observed in early proximal tubular fluid, the glomerulus is the probable source of urinary FN. The FN fragment pattern of early proximal tubular fluid is not substantially altered during passage into final urine, thus reflecting glomerular FN release in urine. It is suggested that examination of urinary FN excretion could be helpful in the assessment of altered glomerular extracellular matrix in pathologic conditions.