The Diffusion Capacity of the Hematoparenchymal Barrier in Mammalian and Marine Fish Skeletal Muscles

Analysis of own and literature data shows that oxygen tension and mass transfer in skeletal muscles of higher and lower vertebrates (mammals, teleosts) are quite comparable. Oxygen consumption in fish muscles is 2–6 times lower and occurs at higher diffusion gradients of PO₂ (blood ? muscles: 45–57 hPa). Wei ghted mean values of PO₂ in fish muscles (with allowance for muscle composition) are minimum (5–12 hPa). As compared to mammals, they exhibit an extremely low diffusion capacity of the hematoparenchymal barrier (0.0014–0.0055 mLO₂ min^–1 100 g^–1 hPa^–1) which appears to rely on diffusion characteristics of cell membranes. Apparently, this is the main reason that accounts for low values of tissue PO₂ as well as low efficacy and oxygen utilization degree in muscles of this taxonomic group of animals.