Title:The Pharmacological Effects of Novokinin; a Designed Peptide Agonist of the Angiotensin AT<sab>2</sab> Receptor
VOLUME: 19 ISSUE: 17
Author(s):Masaaki Yoshikawa, Kousaku Ohinata and Yuko Yamada
Affiliation:Research Institute for Production Development, Prof. Emeritus of Kyoto University, Sakyo-ku, Kyoto 606-0805, Japan.
Keywords:Angiotensin, AT2 receptor, novokinin, compound 21, prostaglandin, vasorelaxation, opioid, food intake,
Abstract:Novokinin (RPLKPW) was designed based on ovokinin (FRADHPFL), a vasorelaxing peptide derived from ovalbumin.
Novokinin relaxed a mesenteric artery isolated from the spontaneously hypertensive rat (SHR) at 10-5 M, and reduced SHR blood pressure
at a dose of 0.1 mg/kg (po.) emulsified in 30% egg yolk. Novokinin exhibited an affinity for the AT2 receptor (Ki = 7 x 10-6M), and
its antihypertensive and vasorelaxing activities were blocked by PD123319, an AT2 receptor antagonist. The hypotensive effect of novokinin
in normotensive mice was not observed in the AT2 receptor-knockout mice. Its antihypertensive and vasorelaxing activities in SHR
were also blocked by CAY-10441, an antagonist of the IP receptor for prostaglandin I2 (PGI2) suggesting that these activities are mediated
by the AT2 receptor, followed by the prostaglandin I2-IP receptor pathway.
Novokinin suppressed food intake after icv. or po. administration in mice. The anorexigenic activity was not observed in the AT2 receptor-
knockout mice, but was observed in the AT1 receptor-knockout mice. The anorexigenic activities of novokinin and angiotensin II
were blocked by PD123319, and ONO-AE3-208, an antagonist of the EP4 receptor suggesting that the anorexigenic activities of the AT2
agonists are mediated by the PGE2-EP4 receptor pathway downstream of the AT2 receptor.
Novokinin given icv. in mice antagonized the antinociceptive effect of morphine. The antiopiod activites of novokinin and angiotensin II
were are blocked by PD123319, and by ONO-AE3-240, an antagonist of the EP3 receptor, suggesting that the antiopioid activities of AT2
agonists is mediated by the PGE2-EP3 receptor downstream of the AT2 receptor.
