Endogenous carbon monoxide formation by chorionic villi of term human placenta

Carbon monoxide (CO) is a novel messenger that is proposed to play a comple mentary role with nitric oxide in the regulation of placental haemodynamics . In a previous study, CO formation from exogenous haem has been measured i n the microsomal fraction of chorionic villi as an index of haem oxygenase activity. The objective of the present study was to determine whether endog enous CO is formed by dissected chorionic villi of term human placenta, to which no exogenous substrate or co-factor had been added. Each sample of fr eshly isolated chorionic villi (approximately 0.4 g) of term human placenta from caesarean delivery was incubated in a scaled vial containing 1 ml of Krebs' solution (pH 7.4) at 37 degreesC. CO formation was determined by qua ntitating, using a gas-chromatographic method, the amount of CO released in to the headspace gas of the incubation vial. There was time-dependent forma tion of endogenous CO in chorionic villi incubated at 37 degreesC during a 60-min time course. CO formation was found to be minimal in chorionic villi samples incubated at 4 degreesC and was increased relative to tissue weigh t. The data demonstrate that there is endogenous CO formation by chorionic villi of term human placenta. (C) 2001 Harcourt Publishers Ltd.