Relationship between Plasma Albumin Concentration and Plasma Volume in 5 Inbred Rat Strains

Using the Evans Blue procedure, we previously found strain-related differences in plasma volumes in 5 inbred rat strains. Because albumin binds strongly with Evans blue, this protein is important in the Evans blue method of plasma volume determination. Therefore, we speculated that interstrain differences in plasma albumin concentration (PAC) could distort calculated plasma volumes. To address this concern, we used ELISA techniques to measure PAC in these inbred rat strains. In study A, the blood volume was measured by using Evans blue dye, and albumin was measured at the start of hemorrhage. In study B, blood volume was not measured, and albumin was measured twice, near the start and end of hemorrhage (approximately 14 min apart). Neither study revealed any interstrain differences in PAC, which decreased after hemorrhage in all 5 strains. No correlation was found between PAC and plasma volume, survival time, blood lactate, or blood base excess. Percentage changes in PAC during hemorrhage were greater in salt-sensitive compared with Lewis rats. Moreover, these percentage changes were associated with survival time in Fawn hooded hypertensive rats. Our data show that the plasma volumes we measured previously were not misrepresented due to variations in PAC.