Abstract Adrenomedullin (AM) is a peptide hormone with multiple physiological functions, which are regulated by its receptor activity–modifying proteins, RAMP2 and RAMP3. We previously reported that AM or knockout (KO) (AM–/–, RAMP2–/–) embryonically lethal in mice, whereas RAMP3–/– mice apparently normal. AM, RAMP2, RAMP3 all highly expressed the heart; however, their functions there not fully...