Assessment of rate of O2 release from single hepatic sinusoids of rats

Characteristics of O2 release from single hepatic sinusoids are described in relation to the sinusoidal O2 inflow for the first time. Microspectroscopic measurement of the rate of O2 release (RO2) from single sinusoids to surrounding hepatocytes was carried out at the edge of the liver of anesthetized rats. The oxyhemoglobin inflow ([HbO2] inflow) into sinusoids, which is a product of sinusoidal blood flow rate and inflowing oxyhemoglobin concentration ([HbO2]), was varied by exchange transfusion of blood with physiological saline. 1) RO2 from single hepatic sinusoids of control rats was fairly constant [0.66 +/- 0.14 (SD) nmol.cm-2.s-1, with 18 sinusoids of 9 rats] over a wide range of [HbO2] inflow (50-200 fmol/s). 2) In the cases of mild anemia, [HbO2] inflow scarcely decreased but RO2 increased, probably because of the increased metabolism of hepatocytes. 3) In the cases of severe anemia, [HbO2] inflow decreased below 50 fmol/s and RO2 decreased accordingly. 4) In all cases no difference was observed between the RO2 values obtained from periportal zone and those from pericentral zone. These results are discussed on the bases of the vascular structure and function of hepatic sinusoids and on the animal model of hemorrhagic shock.