Effect of mode of agitation on storage of platelet concentrates in PL-732 containers for 5 days. 
To determine the degree of damage induced by different modes of agitation during storage of platelets for 5 days in polyolefin (PL-732), we studied pH, platelet count, release of lactic dehydrogenase (LDH) and beta-thromboglobulin (beta-TG), morphology and osmotic recovery.  Platelets were maintained at 20-24 degrees C on elliptical, 6 rpm circular, 2 rpm circular and flat bed agitators.  Results showed that the most and least effective modes of agitation were the 2 rpm circular and the elliptical rotators, respectively.  Elliptical rotators exhibited excessive release of LDH (46%) and beta-TG (51%) while the 2 rpm circular model produced significantly less discharge of these proteins (LDH 13%; beta-TG 30%; p less than 0.05).  With elliptical units, by 120 h of storage, pH was often very alkaline (pH greater than 7.5) when platelet counts were under 1 x 10(9)/ml.  Flat bed shakers and 6 rpm circular agitators were acceptable but flat bed units were unable to resuspend the platelet 'button' which forms after the final preparative centrifugation.  The 2 rpm circular rotator showed significantly less LDH and beta-TG release than did the 6 rpm version (p less than 0.05) and permitted smooth resuspension of the platelet 'button'.  Based on our in vitro studies, we conclude that elliptical rotators may not be suitable for storing PL-732 platelet concentrates and that some other form of agitation should be used.