Neurochemical characterization of preprotachykinin B(50-79) immunoreactivity in the rat.
Preprotachykinin B (PPT-B) contains two peptide sequences which are flanked by pairs of dibasic amino acids: the decapeptide neurokinin B and a 30 amino acid non-tachykinin peptide consisting of the amino acids 50-79 of PPT-B. Whereas the existence of neurokinin B is well established in brain and peripheral tissues, native PPT-B(50-79) has not been identified so far. We have previously studied the distribution of PPT-B(50-79)-immunoreactivity in the rat brain using antibodies directed against synthetic PPT-B(50-79). Now we adapted a radioimmunoassay for characterizing neurochemically PPT-B(50-79)-immunoreactivity in the rat. In the brain concentrations ranging from 2 to 180 fmol/mg wet tissue weight were measured using synthetic PPT-B(50-79) as standard. The highest concentrations were observed in the interpeduncular nucleus and in the hypothalamus (180 and 90 fmol/mg tissue, respectively). Intermediate concentrations (15 to 60 fmol/mg tissue) were present in cortical areas, in the hippocampus, the spinal cord and in the olfactory bulb. Modest levels were detected in the cerebellum. Considerably lower concentrations of PPT-B(50-79)-immunoreactivity were observed in peripheral tissues. They were highest in the adrenal medulla and in the urinary bladder (3.0 and 1.2 fmol/mg tissue, respectively). This distribution, as observed by radioimmunoassay, correlated to that previously revealed by immunocytochemistry. Tissue concentrations of total PPT-B(50-79) immunoreactivity, however, were slightly higher than those of neurokinin B. Gel filtration chromatography on Sephadex G50 and reversed phase HPLC revealed at least three PPT-B(50-79) immunoreactive peaks. About 90% of the PPT-B(50-79)-immunoreactivity was contained within 2 peaks of apparently higher molecular weight than PPT-B(50-79). A minor portion of PPT-B(50-79)-immunoreactivity comigrated with the synthetic peptide, suggesting that only minor amounts of PPT-B(50-79) are formed in vivo. The processing enzyme(s) cleaving protachykinin B at the pair of basic amino acids (Lys80-Arg81) located between PPT-B(50-79) and neurokinin B may not be acting at the Arg48-Arg49 site (followed by -Leu50) at the amino terminal end of PPT-B(50-79).
Lang
S
S
Department of Pharmacology, University of Innsbruck, Austria.
Sperk
G
G
D000595:Amino Acid Sequence; D000818:Animals; D001923:Brain Chemistry; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D015287:Neurokinin B / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D009928:Organ Specificity; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D011498:Protein Precursors / Q000737:chemistry; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism
D010446:Peptide Fragments; D011498:Protein Precursors; C080174:preprotachykinin B (50-79); D015287:Neurokinin B; D007608:Kainic Acid