Publication date: Available online 30 January 2014Source:Peptides Author(s): Yuan Fang , Shuo Li , Huabin Zhou , Xiaozhu Tian , Shuangyu Lv , Qiang Chen Human opiorphin is recently identified endogenous pentapeptide, encoded by ProL1 multigenes family that contributes to cardiovascular modulation. The aim of the study was to evaluate the effect of opiorphin through intravenous injection (i.v.) on mean arterial pressure (MAP) regulation. To investigate the bioactivity of opiorphin, a rat cannulation model was developed for MAP measurement and blood sampling. In our present study, opiorphin (200–700nmol/kg) increased MAP in dose-related and time-dependent manner in conscious rats, which highly associated with the elevation of angiotensin II (AngII) levels in serum. Furthermore, the MAP elevation induced by opiorphin was completely blocked by AngII receptor antagonist valsartan and partially attenuated by angiotensin-converting enzyme inhibitor captopril. Finally, we tested the effect of opiorphin in hypoxia condition, which exhibited that opiorphin reversed hypoxia induced hypotension in conscious rats. Taken together, these results indicated that opiorphin may play an important role in the modulation of blood pressure through AngII dependent pathway, which may help future development of potent clinical therapeutics for emergency treatment.