The Fine Structure of Sickled Hemoglobin in Situ

The sickling of susceptible erythrocytes from patients with sickle cell anemia has been related in previous studies to the intracellular precipitation of reduced sickle hemoglobin (Hb S). Though this knowledge has been available for many years, the form assumed by insoluble reduced Hb S in intact sickled cells has not been previously demonstrated. In the present study, glutaraldehyde incubated with susceptible cells at 37 C. was found to promote the sickling phenomenon as well as preserve the structural form assumed by Hb S after polymerization. Sickled erythrocytes were filled with filaments and rods. The severity of erythrocyte distortion was closely related to the amount of Hb S converted to the rod form and the extent of parallel association of the rods. Cytoplasmic organization in cells sickled by reduced oxygen tension or sodium bisulfite prior to aldehyde fixation was identical to that observed in cells exposed to glutaraldehyde alone. The rods formed by polymerization of Hb S in situ are not morphologically identical to microtubules, but their response to physical and chemical agents suggests that the two types of protein polymers are markedly similar.