Presence of histamine and histamine-metabolizing enzyme in rat and guinea-pig microvascular endothelial cells.
Purified microvascular endothelial cell preparations from guinea-pig perirenal fat pad, heart ventricles and brain cortex were found to contain high histamine methyltransferase (HMT) activity (4, 3, 4.4 and 1.2 nmol of histamine methylated/hr/mg of protein, respectively). The microvascular cells appeared to be the major source of HMT activity in the whole fat pad but not in heart and brain cortex, where the enzyme was present in other cells. The myocyte, for example, was an additional source of HMT activity (1.0 U/mg of protein) in heart. The same preparations from rat had no detectable HMT activity (less than 0.1 U/mg of protein). In contrast to HMT, the second histamine-metabolizing enzyme, diamine oxidase, was found in the microvascular preparations from both species, usually at much higher activity than the parent tissue. All the endothelial cell preparations contained a small (0.1-0.6 microgram/g of tissue; 10-50 ng/mg of protein) pool of histamine which was resistant to the action of Compound 48/80, although the functional significance of this pool is unclear. Thus, in addition to the presence of serotonin- and catecholamine-degrading enzymes, the microvascular endothelium also contains histamine-inactivating enzymes.
D000273:Adipose Tissue / Q000098:blood supply*; D000818:Animals; D002540:Cerebral Cortex / Q000098:blood supply*; D003326:Coronary Circulation / Q000187:drug effects; D006168:Guinea Pigs; D006352:Heart Ventricles; D006632:Histamine / Q000032:analysis*; D006637:Histamine N-Methyltransferase / Q000378:metabolism*; D008297:Male; D008780:Methyltransferases / Q000378:metabolism*; D008833:Microcirculation / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D051381:Rats; D013045:Species Specificity; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
D003189:p-Methoxy-N-methylphenethylamine; D006632:Histamine; D008780:Methyltransferases; D006637:Histamine N-Methyltransferase