This cluster of papers focuses on the function, regulation, and physiological impact of hemoglobin and related proteins in vertebrates. It covers topics such as scavenger receptor CD163 expression, neuroglobin and myoglobin function, haptoglobin phenotype, nitric oxide dioxygenase activity, and the role of flavohemoglobins in detoxifying nitric oxide. The papers also discuss the use of hemoglobin-based oxygen carriers and their potential impact on cardiovascular disease.