| Original language | English (US) |
|---|---|
| Pages (from-to) | 2562-2565 |
| Number of pages | 4 |
| Journal | Biochemical Pharmacology |
| Volume | 27 |
| Issue number | 21 |
| DOIs | |
| State | Published - 1978 |
Funding
To obtain histaminase, human polymorphonuclear Histaminase activity was linear with time for IS hr of leukocytes were isolated from venous blood of a normal incubation (Fig. 1, left panel). Activity was completely donor by Hypaque-Ficoll density centrifugation [13]. abolished by 10-j M aminoguanidine, a specific inhibitor Contaminating erythrocytes were removed by hypotonic of diamine oxidase 1141. A Lineweaver-Burk plot of Iysis and the PMN suspended at lo7 cells/ml in a 0.025M activity vs substrate concentration yielded a Km of Tris buffer, pH 7.4, containing 0.3 m&ml of human 2.4 x lo-” M (Fig. 1, right panel). This value agrees with serum albumin, 0.6 mM CaCI,, and 1 mM MgQ the K, of 2.5 x lo-” M reported by Zeiger et al. [3] for (TACM) [I]. One-ml volumes of the PMN suspension histaminase activity of human PMN lysates. It also were incubated with 5 pgfml of A23187 (suspended in corresponds closely to the K,,, of 2.8 x 10-O M obtained buffer) for 30 min at 37”. Zeiger et al. [3] demonstrated for histaminase purified from human placenta [IS]. that A23187 releases all of the intra~llul~ histaminase Sig~ficant i~ibition of histaminase activity was activity within 30 min and this has been confirmed in our observed with each of the three H-2 antagonists at laboratory. Incubations were stopped by a Zmin centri-concentrations of IV M and greater (Fig. 2). Burimam-fugation at 1OOOgand the cell-free supernatant fractions ide was particularly potent, c&sing complere inhibition were pooled. The pooled supernatant fraction was diluted at 1O-5 M. In contrast, diphenhydramine, an H-l antag-1 : 1 with buffer to yield activity derived from 5 x lo6 onist, possessed minimal inhibitory activity; pyrilamine, PMN/ml and divided into aliquots for storage at - 20”. chlorpheniramine and cyclizine were similarly without Histaminase activity was measured by the method of etiect. Of the H-l antagonists examined, only prometha-zine produced significant inhibition (50 per cent at lo-” M * Publication No. 316 from the O’Neill Research but none at lO-SM). Thus, with the possible exception of Laboratories. The Good Samaritan Hospital, 5601 Loch the oh~nothiaziIle class. the i~ibition was specific for the Raven Blvd, Baltimore, MD 21239. This. work was H-2-antagonists. The’ inhibition by phenothiazines is supported in part by National Institutes of Health being pursued further. A similar pattern of inhibition was Grant AI 11334. obtained for H-2 antagonists with histaminase prepared 2562
ASJC Scopus subject areas
- Biochemistry
- Pharmacology