Haem oxygenase activity in human umbilical cord and rat vascular tissues. 2000

H J Vreman, and R J Wong, and E C Kim, and D C Nabseth, and G S Marks, and D K Stevenson
Department of Pediatrics, Division of Neonatal and Developmental Medicine, Stanford University School of Medicine, Stanford, CA, 94305-5119, USA. henk.vreman@stanford.edu

Carbon monoxide (CO) has been shown to affect vascular tone in smooth muscle cells and thus, may regulate regional or systemic blood pressure as well as fetoplacental vascular tone and fetal blood delivery. To assess the potential of vascular tissue to produce CO, we determined haem oxygenase (HO) activity through in vitro quantitation of CO production with gas chromatography and its inhibition by 33-66 microm of chromium mesoporphyrin (CrMP) in homogenate preparations of rat aorta and vena cava and human umbilical cord tissues. We compared these results to HO activity in rat heart and liver. We also discuss normalization of HO activity on a per mg protein as well as per g fresh weight (FW) tissue basis. We found that both rat vascular tissue HO activities (per g FW) were equal, but greater than that of heart (x3) and less than that of liver (x0.2). For human cord tissues, HO activities of artery and vein were equal, but greater than that of Wharton's jelly. Also, HO activity in rat vascular tissues was 3x greater than that of the human cord tissues. HO activity was completely inhibited by CrMP in rat heart (90 per cent) and liver (96 per cent), but incompletely (50-66 per cent) in both rat and human vascular tissues. We established that it is unlikely that other non-haem CO-generating processes account for this unique insensitivity of HO to CrMP inhibition. In fact, high concentrations of other potent metalloporphyrin inhibitors affected vascular tissue HO even less. We found that the degree of in vitro HO inhibition appeared to be related to the concentration of haem in the reaction medium. We conclude that the presence of HO activity in cord tissues supports the possibility that CO plays a role in fetoplacental blood flow regulation.

UI MeSH Term Description Entries
D007231 Infant, Newborn An infant during the first 28 days after birth. Neonate,Newborns,Infants, Newborn,Neonates,Newborn,Newborn Infant,Newborn Infants
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D008297 Male Males
D008665 Metalloporphyrins Porphyrins which are combined with a metal ion. The metal is bound equally to all four nitrogen atoms of the pyrrole rings. They possess characteristic absorption spectra which can be utilized for identification or quantitative estimation of porphyrins and porphyrin-bound compounds. Metalloporphyrin
D002248 Carbon Monoxide Carbon monoxide (CO). A poisonous colorless, odorless, tasteless gas. It combines with hemoglobin to form carboxyhemoglobin, which has no oxygen carrying capacity. The resultant oxygen deprivation causes headache, dizziness, decreased pulse and respiratory rates, unconsciousness, and death. (From Merck Index, 11th ed) Monoxide, Carbon
D002857 Chromium A trace element that plays a role in glucose metabolism. It has the atomic symbol Cr, atomic number 24, and atomic weight 52. According to the Fourth Annual Report on Carcinogens (NTP85-002,1985), chromium and some of its compounds have been listed as known carcinogens.
D004791 Enzyme Inhibitors Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction. Enzyme Inhibitor,Inhibitor, Enzyme,Inhibitors, Enzyme
D006419 Heme Oxygenase (Decyclizing) A mixed function oxidase enzyme which during hemoglobin catabolism catalyzes the degradation of heme to ferrous iron, carbon monoxide and biliverdin in the presence of molecular oxygen and reduced NADPH. The enzyme is induced by metals, particularly cobalt. Haem Oxygenase,Heme Oxygenase,Oxygenase, Haem,Oxygenase, Heme
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia

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