Detection of N-terminally extended substance P but not of substance P in human cerebrospinal fluid: quantitation with HPLC-radioimmunoassay.
A reversed-phase HPLC system was used to concentrate and separate components of substance P-like immunoreactivity (SP-LI) from human CSF. When CSF was injected and fractions collected, no SP-LI could be detected by radioimmunoassay (RIA) at the retention time of SP or SP-sulfoxide. Instead, SP-LI was detected in later eluting fractions. This SP-LI reacted with two different antisera raised against the C-terminal part of SP, but not with an antiserum against the N-terminal part. A compound with similar properties was also found to be present in neutral extracts of rat dorsal spinal cord. When the late-eluting compound from human CSF was treated with trypsin and rechromatographed on HPLC, an immunoreactive component eluting at the position of SP could be detected with both the C- and N-terminally directed SP antisera. These results suggest that an N-terminally extended form of SP is present in human CSF. Trypsinization also gave two other compounds with affinity for the N- but not the C-terminally directed antisera. This may indicate that N-terminal fragments of SP extended at the N-terminus or SP molecules extended at both the N- and the C-terminus (i.e., preprotachykinins) also are present in human CSF. In 32 CSF samples from depressed patients, SP-LI was determined with a C-terminally directed antiserum with and without prior HPLC separation. SP itself could not be detected, but the late-eluting form of SP-LI could be quantitated in all samples by combined HPLC-RIA. In most samples, there was a relatively good agreement between the SP-LI levels measured with and without HPLC.
D000918:Antibody Specificity; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007106:Immune Sera / Q000276:immunology; D010446:Peptide Fragments / Q000134:cerebrospinal fluid* / Q000276:immunology; D011863:Radioimmunoassay; D013373:Substance P / Q000134:cerebrospinal fluid* / Q000276:immunology; D014357:Trypsin / Q000378:metabolism
D007106:Immune Sera; D010446:Peptide Fragments; D013373:Substance P; D014357:Trypsin