Effects of sodium chloride, Triton X-100, and alkaline pH on the measurable contents and sedimentability of the nerve growth factor (NGF) antigen in adult rat hippocampal tissue extracts

Abstract

Nerve growth factor (NGF) was found to be largely associated with sedimentable fractions of hippocampal and other neural tissues of the adult rat (Hoener et al.: Brain Res 728:47-56, 1996), verified by both bioassay and ELISA techniques. In the present study, the ELISA assay conditions were improved and simplified. Bovine serum albumin was needed in the phosphate buffered saline for maximal measurability of NGF antigen. Hippocampal tissue sonicates were separated into nonsedimentable supernatant and sedimentable pellet fractions. Individual or combined treatments with sodium chloride, Triton X-100, and pH were applied to the samples for possible effects on the i) measurable content of NGF antigen and ii) distribution of sedimentable and nonsedimentable forms. The amount of measurable NGF antigen was found to be increased in a dose dependent fashion by sodium chloride between 0.15 and 0.35 M, Triton X-100 between 0 and 0.5%, and pH between 8.5 and 10.5. The same treatment that led to maximal measurable NGF levels (0.7% Triton X-100 and pH 10.5) also caused the release of the NGF antigen from sedimentable to nonsedimentable fractions. Similar findings regarding maximal NGF antigen levels and release were seen for treatments applied to the sonicate before separation into a supernatant and pellet fraction.