DISTRIBUTION AND METABOLISM PATTERNS OF PLASMA 7S-NGF AND BETA-NGF INTHE ADULT MALE-RAT

There is a great deal of controversy on the existence of NGF in body f luids and tissues. To date it remains unknown whether this peptide acc umulates preferentially at significant levels in different organs. Thu s we undertook the evaluation of kinetic parameters of the disappearan ce of blood of I-125-7S-NGF and I-125-beta-NGF after intravenous injec tion in male adult rats. Our results indicate that the plasma half-lif e of I-125-7S-NGF is approximately twice as long as for I-125-beta-NGF (respectively 61.7 +/- 11.7 min and 36.3 +/- 2.2 min) while the distr ibution volume is not significantly different between both peptides. F urthermore, the uptake of radioactive NGF by different tissues seems v ery low as shown by I-125-7S-NGF and I-125-beta-NGF content of the sam pled organs compared to the plasma concentration at the same time. The se results indicate that the tissue uptake of circulating 7S and beta- NGF is very low in the adult rat. Thus in these animals NGF did not cr oss the blood-brain barrier and did not accumulate in peripheral organ s which are known to contain subsequent amounts of this peptide. This lack of deposition might be due to a binding with plasma proteins (pro bably alpha 2-macroglobulin).