Hemoglobin absorption in the proximal tubules of the kidney in the rabbit

Relatively small quantities of hemoglobin, 1.5 mg per cubic centimeter of blood, were injected intravenously into rabbits, and ultrastructural changes in the proximal tubular epithelial cells of the kidney were followed over a 24-hour period. These experiments and prior experiments have shown that the hemoglobin is absorbed by proximal tubular cells of the kidney, but the manner that it gets into the cytoplasmic organelles remains uncertain. The hemoglobin is segregated into apical vacuoles and then either transferred to type II A, B, and C cytoplasmic bodies or the vacuoles become changed into these types of cytoplasmic bodies. Definite evidence of metabolism has not been shown in these experiments, but observations would seem to indicate that the type II cytoplasmic bodies which do contain acid phosphatase in addition to hemoglobin are involved in the metabolic process. The observations of microvesicles and different types of apical tubules and their possible functions are indicated and discussed. Also described is a peculiar cytoplasmic body which apparently has not been described before and which may be peculiar to this species of rabbit.