Aj. Okragly et M. Haakfrendscho, AN ACID-TREATMENT METHOD FOR THE ENHANCED DETECTION OF GDNF IN BIOLOGICAL SAMPLES, Experimental neurology, 145(2), 1997, pp. 592-596
Glial cell line-derived neurotrophic factor (GDNF), a distant member o
f the transforming growth factor-beta (TGF beta) family, is a protein
that is essential for the survival of dopaminergic, motor, and periphe
ral neurons. To facilitate its study, we and others have developed sen
sitive (low pg/ml) enzyme-linked immunosorbant assays (ELISA) to quant
itate endogenous concentrations of GDNF, along with neurotrophin-3 (NT
-3) and nerve growth factor (NGF). However, endogenous tissue levels o
f GDNF in adult animals are not readily detected by ELISA and do not c
orrelate well with message RNA. Based upon previously described method
s for the extraction of TGF beta from tissue samples, we have develope
d an acid-treatment procedure to allow the quantification of total end
ogenous GDNF. This procedure also was evaluated for use when measuring
total endogenous levels of NT-3 and NGF from biological samples. The
acid-treatment procedure increases the detectable amounts of GDNF, NT-
3, and NGF in all tissue samples and most of the serum samples tested.
Moreover, these values were as much as 35 times greater than those de
tected using traditional extraction buffers. Such elevated concentrati
ons likely resulted from the acid treatment promoting the dissociation
of ligands from receptors or binding proteins, thereby making more of
the analyte available to be measured in the ELISA. These findings ind
icate that appropriate sample treatment is essential for the measureme
nt of total endogenous neurotrophic factors. (C) 1997 Academic Press.