Electron microscope and ultracentrifugation studies on the rat reticulocyte

Abstract

Reticulocytosis was induced in rats by the daily injections of phenylhydrazine. The reticulocytes were studied by supravital staining, ultracentrifugation and phase‐contrast and electron microscopy. Electron micrographs of sectioned reticulocytes reveal the presence of hemoglobin, polyribosomes, mitochondria, micropinocytosis vesicles, tubules of varying size and, in some cases, Heinz body material. When subjected to ultracentrifugation these materials are readily stratified in the order of their relative densities from the centrifugal to the centripetal end as follows: hemoglobin, mitochondria, ribonucleoprotein material (ribosomes) and Heinz body material. The centrifuged reticulocytes may be stretched two or three times their normal diameter and even pulled into two parts without hemolysis. Of interest is the observation that in ultracentrifuged reticulocytes, the ribosomes are not displaced from the region of the cortex, a condition which is interpreted as strong evidence that this region is of a greater consistency (viscosity) than the remainder of the cell. Evidence was observed to show that as maturation of the reticulocyte occurs, the cell gradually decreases in size and increases in density; concomitantly with these changes is a progressive degradation of the mitochondria and ribonucleoprotein material, so that by the time the erythrocyte stage is reached, these materials seem to have completely disappeared.