Plasma tetranectin in healthy male and female individuals, measured by enzyme-linked immunosorbent assay.

Tetranectin is a novel protein recently isolated from human plasma. It is a tetramer, composed of four identical, non-covalently bound, 181-amino-acid polypeptide chains (Mr = 20,100). We report here the quantification of plasma tetranectin in 457 healthy individuals, aged from birth to 85 years, using a newly developed sensitive and reproducible enzyme-linked immunosorbent assay (ELISA). Tetranectin was demonstrable in all subjects investigated, and within each sex and defined age group the concentration was well controlled within a relatively narrow range. The mean plasma tetranectin level in newborn infants (cord plasma) was about 8 mg/L. This was significantly less than in later life, during which mean plasma tetranectin level varied between 10 and 12 mg/L. After the age of 9 years, tetranectin level was continuously higher in males than in females, but the variations through the span of life were almost identical. Thus, a transitory increase in plasma tetranectin was observed in early puberty, reaching its climax about the age of 11 to 12 in girls and 14 to 15 in boys. A quantitatively similar, additional peak was observed during the period of 50 to 59 years of age in both sexes, whereupon the tetranectin concentration gradually decreased. The biologic function of tetranectin remains to be elucidated. Recently, we have reported that tetranectin is contained within hepatocytes and various endocrine cells, all known to process peptide hormones or glucoproteins. We propose that tetranectin may be involved in intracellular and extracellular serine protease-mediated proteolysis.