The release of acetylcholinesterase from human erythrocytes by sodium taurocholate.

Glycocholate and taurocholate have been shown (Coleman & Holdsworth, 1976; Billington & Coleman, 1978) to release significant amounts of membrane proteins and phospholipid from erythrocytes before the occurrence of significant cell lysis. Our particular interest was to study in detail the release of acetylcholinesterase from human erythrocytes. Heparinized human blood was centrifuged at 2500g for 10min. After removing the plasma and buffy coat the cells were washed four times with approx. 3Ovol. of 154m~-NaCi / . 1.5 mM-Bicine ~NN-bis-(2-hydroxyethyl)glycinel buffer, pH 7.4. A 1 : 1 suspension of the washed cells in 105m~-NaCI/ 50m~-Bicine buffer (pH varied) was made. Of this suspension lvol. was incubated at 37OC (time varied) with 3vol. of the above buffer containing different concentrations of sodium taurocholate (Weddel Pharmaceuticals, Clwyd, N. Wales LL139 PX, U.K.). Supernatants were obtained by centrifuging at 14000g for 2min. Acetylcholinesterase activity in the supernatant was assayed spectrophotometrically (Ellman et al., 1961). The extent of erythrocyte lysis was determined by measuring the absorbance of the supernatants at 525 nm. The 100% values (acetylcholinesterase activity and haemoglobin) was determined on uncentrifuged controls. It was assumed that