We evaluated protocols for the extraction of calcitonin gene-related p
eptide, neuropeptide Y, substance P, peptide YY and beta-endorphin fro
m rat lung tissue for subsequent radioimmunoassay. The effects of vary
ing acidity of the extraction solution and repeating extraction on the
recovery of peptide immunoreactivity and non-specific tracer-binding
were compared by analysis of variance. Moreover, variability of immuno
reactivity was quantified for comparison. Considering all three criter
ia, the optimal acidity for extraction was: 0.1 M or 1 M acetic acid f
or CGRP and beta-endorphin, 0.1 M acetic acid for NPY, 1 M acetic acid
for substance P and phosphate buffer for peptide YY. Double or combin
ed extraction unambiguously improved assay results only for substance
P. Reversed-phase high-performance liquid chromatography of CGRP-, NPY
- and SP-immunoreactivity obtained from selected extracts suggested th
at differences in recovery of these peptides are not explainable by di
fferential peptide fragmentation during extraction. (C) 1997 Elsevier
Science Inc.