Neuromedin U-8 and U-25: novel uterus stimulating and hypertensive peptides identified in porcine spinal cord.

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.