Evidence is accumulating that carbon monoxide (CO) can be an endogenous regulator of various physiologic processes in the brain and vascular tissues. CO is primarily a product of the heme catabolic pathway, of which the enzyme, heme oxygenase (HO), controls the rate limiting step and is responsible for the production of CO from erythropoietic- and hemoprotein heme. CO has been shown to affect vascular tone in smooth muscle cells. Thus, CO could be a factor in regional or systemic blood pressure regulation. We determined HO activity and its in vitro inhibition by 33 μM of chromium mesoporphyrin (CrMP) in homogenate preparations of rat aorta, vena cava and human umbilical cord artery and vein and Wharton's jelly and compared it to activity in rat liver. HO activity (mean±SD) was determined by measuring the in vitro production rate of CO with gas chromatography: Table We conclude that vascular tissue preparations have HO activity comparable to that in liver. The study of CO biology in vascular structures may provide insight into the control of regional or systemic blood flow during development.

Table 1
Full size table

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