1988 年 5 巻 2 号 p. 135-144
A highly sensitive two-site enzyme immunoassay system for mouse β-nerve growth factor (β-NGF) was developed, based on the sandwiching of the antigen between anti-β-NGF IgG antibody coated on a polystyrene bead and anti-β-NGF Fab' antibody-linked peroxidase (horseradish peroxidase, EC 1.11.1.7). Its discriminatory sensitivity was as low as 1pg/ml. Using this enzyme immunoassay system, we examined the levels of β-NGF in various tissues, serum, and plasma of mice. Among these, the level of β-NGF in submaxillary gland was found to be extremely high, as has been reported previously. Also, low levels of β-NGF were detected in the other tissues, serum, and plasma. The level in spleen was found to be relatively high compared with the levels in all but the submaxillary gland. To examine the molecular nature of NGF in plasma, serum or plasma was applied to a column of Sephadex G-100. β-NGF-like immunoreactive substance(s) appeared over a range from the void volume to the position at which a protein having a molecular weight of about 13, 000 daltons elutes. A major peak was observed at an elution position corresponding to a molecular weight of approximately 21, 000. By reducing serum or plasma with dithiothreitol, the elution profile was altered remarkably and the broad peak with β-NGF-like immunoreactivity was converted into two fractions, one appearing in the void volume and the other at the position corresponding to β-NGF. These results indicate that a part of the β-NGF may circulate as a complex form with some macromolecule(s) through disulfide linkage(s) in mouse plasma.
