Chapter 7 - The Erythrocyte: Physiology, Metabolism, and Biochemical Disorders

Abstract

This chapter discusses the physiology, metabolism, and biochemical disorders of erythrocytes. Mammalian erythrocytes or red blood cells (RBCs) are anucleate cells that normally circulate for several months in blood despite limited synthetic capacities, and repeated exposures to mechanical and metabolic insults. The primary purpose of RBCs is to carry hemoglobin (Hb), a heme-containing protein that accounts for more than 90% of the protein within RBCs. Most RBCs in normal dogs, cats, horses, cattle, and sheep occur in the shape of biconcave disks (discocytes). The degree of biconcavity is most pronounced in dogs, and less so, in cats and horses. RBCs from goats generally have a flat surface with little surface depression; a variety of irregularly shaped RBCs (poikilocytes) may be present in clinically normal goats. This chapter begins with a discussion on differences in erythrocyte shape and functions of RBCs. The chapter then elaborates concepts related to hematopoietic microenvironment and hematopoietic growth factors. Biochemistry of iron metabolism, Hb synthesis, and reticulocytes are also discussed. The chapter explains in detail the membrane structure of RBCs, as well as concepts related to shape and deformability, membrane transport, and carbohydrate metabolism. The chapter concludes with discussing inherited disorders of RBCs.