A new biologically active
peptide of the
neurotensin (NT) family, shown previously to cross-react in a COOH-terminal-directed radioimmunoassay for bovine NT, has been isolated from extracts of chicken intestine and identified as
H-Lys-Asn-Pro-Tyr-Ile-Leu-OH, which is identical with the biologically active COOH-terminal half of NT except for the amino acid substitutions Lys/Arg and Asn/Arg. It is proposed that this
peptide be referred to as Lys8, Asn9, NT8-13 (LANT-6). Synthetic material prepared with this amino acid sequence using the Merrifield technique was immunochemically, chromatographically, and biologically indistinguishable from the native
peptide. In contrast to chicken NT which
induced hypotension,
hyperglycemia, increased vascular permeability, and
cyanosis when injected intravenously into anesthetized rats, synthetic
LANT-6 brought about primarily a hypertensive response and had little ability to promote
hyperglycemia, increased vascular permeability, and
cyanosis. In rats pretreated with the alpha-blocker
phentolamine and in adrenalectomized rats, the hypertensive response to
LANT-6 was blocked, suggesting that adrenal
catecholamines mediated this effect. These findings suggest that
LANT-6, a natural variant of NT with a different spectrum of
biologic activity, may be a NT-related messenger
peptide with a different function(s).