Characterization of beta-lactotensin, a bioactive peptide derived from bovine beta-lactoglobulin, as a neurotensin agonist.
beta-Lactotensin (beta-LT: His-Ile-Arg-Leu) is an ileum-contracting peptide derived from residues No. 146-149 of bovine beta-lactoglobulin. The ileum-contracting activity of beta-LT was blocked by the NT1 antagonist SR48692. beta-LT was selective for the neurotensin NT2 receptor while neurotensin was selective for the NT1 receptor. beta-LT is the first natural ligand showing selectivity for the NT2 receptor. beta-LT showed hypertensive activity after intravenous administration at a dose of 30 mg/kg in conscious rats, while neurotensin showed hypotensive activity. The hypertensive activity of beta-LT was blocked by levocabastine (1 mg/kg, i.v.), an NT2 antagonist. SR48692, which blocked the hypotensive activity of neurotensin, had no effect on the hypertensive activity of beta-LT. These results suggest that the hypertensive activity of beta-LT is mediated by the NT2 receptor. It was concluded that the NT1 and NT2 receptors mediate the opposite effect on blood pressure.
Yamauchi
Rena
R
Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Uji, Kyoto 611-0011, Japan.
Usui
Hachiro
H
Yunden
Jinsmaa
J
Takenaka
Yasuyuki
Y
Tani
Fumito
F
Yoshikawa
Masaaki
M
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002417:Cattle; D006168:Guinea Pigs; D006801:Humans; D007082:Ileum / Q000187:drug effects; D007782:Lactoglobulins; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009496:Neurotensin / Q000819:agonists*; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D018028:Receptors, Neurotensin / Q000378:metabolism
D007782:Lactoglobulins; D009842:Oligopeptides; D018028:Receptors, Neurotensin; C102984:beta-lactotensin; C114036:neurotensin type 1 receptor; D009496:Neurotensin