EGTA-extractable calmodulin in platelet membrane is lower in alcoholics than in controls

The purpose of this study was to determine calmodulin distribution in platelets of alcoholics. Eight alcoholics were diagnosed by DSM-III (Diagnostic and Statistical Manual of Mental Disorders, 3rd edition) criteria prior to admission to the Alcohol Unit, VA Hospital, San Antonio, TX. Whole blood was drawn after a five day washout period, and again after 30 days of disulfiram treatment. Platelets were prepared from the whole blood, suspended in Ringer's-citrate-dextrose buffer (RCD), divided into 2 aliquots, then sonicated and centrifuged (100K × g). Supernatants were assayed for calmodulin content by RIA. The pellets were resuspended by sonication in 1 mM EGTA in RCD or 1% (w/v) Lubrol-PX in RCD, then centrifuged at 100K × g. Calmodulin was measured in the EGTA and Lubrol supernatants. EGTA-extractable calmodulin in pre-disulfiram, post-disulfiram, and control subjects was 5.07±2.2 (SD), 5.19±1.7 (SD), and 10.5±6.7 (SD) ng calmodulin/mg whole platelet protein. The EGTA-extractable calmodulin was significantly lower in alcoholics pre- or post-disulfiram than in controls (p<0.025). These preliminary results suggest an alteration in platelet membranes of alcoholics that affects the binding of calmodulin.