CARBAMYLATION OF ERYTHROCYTE-MEMBRANE AMINOPHOSPHOLIPIDS - AN IN-VITRO AND IN-VIVO STUDY

Objectives: To study the binding of cyanate to erythrocyte membrane am inophospholipids in vitro, and to investigate whether carbamylated ami nophospholipids can be detected in the plasma membrane of native eryth rocytes. Design and Methods: For in vitro studies, the lipid component s of C-14-carbamylated erythrocyte membranes were resolved by thin-lay er chromatography (TLC). The covalent incorporation of cyanate was vis ualized by autoradiography and quantitated by phosphorus analysis. For the in vivo studies, phospholipid headgroups were enzymatically hydro lyzed by phospholipase D and subsequently reacted with diacetyl monoxi me. Results: Both phosphatidylethanolamine (PE) and phosphatidylserine (PS) were covalently modified by [C-14] cyanate; incorporating 15.76 +/- 0.09 and 13.34 +/- 0.81 mol%, respectively, following a 15-h incub ation. Carbamylated PE (carb-PE) was resolved with PE by TLC in a solv ent system consisting of chloroform/methanol/ammonia (65/35/5, v/v/v). Treatment of native erythrocyte membrane lipid micelles with phosphol ipase D, followed by reaction with diacetyl monoxime, suggests the pre sence of intrinsic carb-PE (2.85 +/- 0.65 percent of the total PE). Co nclusions: Carbamylation of erythrocyte aminophospholipid may be invol ved in some of the hematological consequences of uremia on the erythro cyte.