Hexachlorophene (HCP), pentachlorophenol (PCP), 2,4,5-trichlorophenol (2,4,5-TCP) and 2,4,6-trichlorophenol (2,4,6-TCP) all hemolyzed washed human erythrocytes and inhibited acetylcholinesterase (AchE) activities in erythrocyte membrane. HCP was much more potent in either effect than any other compound examined. The inhibition of AchE activities by HCP was reversed on adding albumin. The dose-response curves by HCP and PCP were sigmoidal, indicating cooperative inhibition, while those by 2,4,5-TCP and 2,4,6-TCP were not. Furthermore, the cooperativity of the inhibition by HCP was greater than by PCP. Differing from that by PCP, the cooperativity of inhibition increased depending on the temperature (13, 25, 37 degrees C) and decreased when the membrane was treated with Triton X-100. The cooperativity was also decreased in the presence of albumin. On a Scatchard plot analysis, erythrocyte membranes appeared to have multiple binding sites of different affinities for HCP; binding of HCP to the low affinity site [dissociation constant (Kd) 4.7 x 10(-5) M] seemed to be responsible for the observed cooperative inhibition of AchE activities. Neither neostigmine nor fenitrothion altered the cooperativity. HCP seems to be the most potent cooperative inhibitor of AchE in human erythrocyte membranes known to date. HCP may be useful to examine AchE and milieu in human erythrocyte membranes.
Lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) activities and total protein concentrations were examined in the postrinsing solutions from rat lungs preserved in phosphate-buffered saline (PBS), Euro-Collins (E-C) solution, or low-potassium E-C solution for 8 h at 4 degrees C, 10 degrees C, or 20 degrees C. The LDH and AST activities were higher when the organs were preserved in PBS for 8 h at 20 degrees C than at 4 degrees C or 10 degrees C, while the total protein concentration did not differ according to the temperature or solution. The activities were also higher when the lungs were preserved in Euro-Collins (E-C) solution than in PBS or the low-potassium E-C solution. On examining pulmonary functions utilizing an ex vivo reperfusion model, the lungs preserved at 20 degrees C showed poorer gas exchange than those preserved at 4 degrees C or 10 degrees C. Moreover, the organs preserved in E-C solution showed poorer function than those preserved in any other solution. These findings suggest that some enzymatic activities in the postrinsing solution could be indicators of lung viability after preservation.
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