Human Endogenous Metabolite
Potency to stimulate contraction of rat uterine smooth muscle, that is used as bioassay for isolation of Neuromedin B (NMB), is compared with Bombesin (BN). The relative potency, calculated on molar basis by taking BN as 100, is 48% for GRP and 4.9% for NMB. NMB also has contractile activity on rat stomach strip, but the potency (ratio of peptide concentration required to elicit 50% maximum response; EC 50 ) is only 5% of BN (EC 50 of BN/EC 50 of NMB) and about 10% of GRP (EC 50 of GRP/ EC 50 of NMB).
Potencies of NMB and GRP for smooth muscle contraction of fundus in wild-type and NMB-R-deficient mice with ED 50 of 14.4±2.3 (n=8) and 10.9±2.3 (n=8) in wild-type mice and NMB-R-deficient mice, respectively.