888 FORMATION AND REMOVAL OF POCKED ERYTHROCYTES STUDIES IN HUMAN SUBJECTS AND LABORATORY ANIMALS

Abstract

The “pit count” or pocked erythrocyte (Pk RBC) count (PC) is the percentage of RBCs containing one or more vesicles visualized by phase interference microscopy. The PC is <1.5% in normal subjects and 25-60% in surgically splenectomized patients; values between these extremes may result from splenic hypofunction. Although the PC is being increasingly utilized as a test of splenic function, little information is available about the patterns of formation and removal of these organelles. We performed serial PCs following splenectomy (S) in 4 patients. Levels began to rise within 1 week and reached a plateau (30-50%) by 6 to 8 weeks. Similar results were obtained following S of dogs, except that the steady state plateau value was only 10-13%. Rats initially exhibited a similar pattern of rise in PC post-S, but from the 4th to 10th week the PC gradually declined to 3%; splenosis or accessory spleens were not visualized at autopsy. Rabbits had only a slight and inconsistent rise in PC after S. Rate of removal from the circulation of Pk RBCs was determined by exchange transfusion of blood from a splenectomized dog into a eusplenic animal. Clearance of the Pk RBCs was linear, with a t1/2 of 8 hours. We conclude that Pk RBCs rise slowly following S, rapidly disappear from the circulation in the presence of a normal spleen, and vary in the pattern of rise and peak levels following S among different animals.

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