1. Structure-activity relationships of neuromedin U. V. study on the stability of porcine neuromedin U-8 at the C-terminal asparagine amide under mild alkaline and acidic conditions
Tadashi Hashimoto, Yuki Sato, Akira Shibata, Naoki Sakura, Takako Kawai, Katsuro Kurosawa, Sachiko Kato, Kazuhiro Ohki Chem Pharm Bull (Tokyo) . 2006 May;54(5):659-64. doi: 10.1248/cpb.54.659.
Porcine neuromedin U-8 (X-Asn-NH(2), X=H-Tyr-Phe-Leu-Phe-Arg-Pro-Arg) is occasionally unstable in the biological fluids used for bioassay as well as in the acidic solutions used for purification of synthetic peptides. In this study, HPLC examination of an incubate solution of X-Asn-NH(2) revealed that the main decomposition products in Tyrode's solution (pH 7.4) were either alpha- or beta-monocarboxylic acid analogs (X-Asn-OH or X-Asp-NH(2)), and that no dicarboxylic acid analog (X-Asp-OH) was produced. Further investigation, employing a model peptide (Y-Asn-NH(2), Y=Benzoyl-Pro-Arg) incubated in a 0.1 M sodium bicarbonate solution at 60 degrees C, revealed that the decomposition of C-terminal Asn-NH(2) occurred through the formation of an aminosuccinimide intermediate (Y-Asu), at a rate faster than that of Y-Asn-Ser peptide but slower than that of Y-Asn-Gly peptide. Mild acid hydrolysis of X-Asn-NH(2) examined in a 1 M HCl solution at 60 degrees C yielded X-Asn-OH and X-Asp-NH(2), which further decomposed to yield X-Asp-OH. The C-terminal degradation of X-Asn-NH(2) resulted in reduced biological and immunochemical binding activities.
2. Effect of synthetic neuromedin U-8 and U-25, novel peptides identified in porcine spinal cord, on splanchnic circulation in dogs
S Sumi, T Tobe, K Inoue, K Takaori, R Doi, H Yajima, T Suzuki, M Kogire Life Sci . 1987 Sep 28;41(13):1585-90. doi: 10.1016/0024-3205(87)90725-9.
Two novel peptides which exert a potent stimulant effect on rat uterus smooth muscle have recently been identified in porcine spinal cord. These peptides designated neuromedin U-8 and U-25 have been reported to exert a hypertensive effect in rats. But further biological activities are not known. In the present study, the effect of these peptides on blood flow in portal vein, superior mesenteric artery and pancreatic tissue and on blood pressure were examined in dogs, utilizing recently developed ultrasonic transit time volume flow meter and laser Doppler flow meter. Neuromedin Us potently reduced blood flow in superior mesenteric artery. The minimum reductions could be observed even at very small doses of neuromedin U-25 (32 fmol/kg) and U-8 (90 fmol/kg), while the maximal reductions of 48.4 and 51.0% were attained at the doses of 320 pmol/kg (U-25) and 900 pmol/kg (U-8), respectively. These peptides also reduced portal vein blood flow, and the maximal reductions of 42.1 and 37.2% were attained at the doses of 32 pmol/kg (U-25) and 90 pmol/kg (U-8), respectively. On the other hand, blood flow in pancreatic tissue increased slightly with the maximal increases of 13.8% at 3.2 pmol/kg (U-25) and 11.8% at 9 pmol/kg (U-8), respectively. The maximal increases of blood pressure were 5.2% at 320 pmol/kg (U-25) and 4.3% at 90 pmol/kg (U-8). Furthermore, neither neuromedin U-25 nor U-8 influenced the axillary artery blood flow, suggesting their selective effect on splanchnic blood flow. Because of the potent and probably selective activity on splanchnic circulation, neuromedin U-25 and U-8 may well be recognized as physiologically significant novel neuropeptides or hormones.
3. Neuromedin U-8 and U-25: novel uterus stimulating and hypertensive peptides identified in porcine spinal cord
N Minamino, H Matsuo, K Kangawa Biochem Biophys Res Commun . 1985 Aug 15;130(3):1078-85. doi: 10.1016/0006-291x(85)91726-7.
Two novel peptides eliciting a potent stimulant effect on the rat uterus smooth muscle have been purified and identified in porcine spinal cord. These peptides were designated as neuromedin U-8 (8 amino acids long) and U-25 (25 amino acids long) referring to their uterus stimulating activity. Sequence analyses and syntheses revealed that neuromedin U-8 is a novel octapeptide with a C-terminal amide structure, while U-25 contains the U-8 sequence at its C-terminus, preceded by paired Arg residues, implicating their biosynthetic relationship. Their potent uterus stimulating activity and hypertensive effect, as well as their unique C-terminal amide structure are indicative of their specialized physiological function.
