AJP - Heart Calcium Transients and Cell-Sarcomere
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Am J Physiol Heart Circ Physiol 286: H121-H130, 2004. First published August 28, 2003; doi:10.1152/ajpheart.01136.2002
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Effects of Hct and norepinephrine on segmental vascular resistance distribution in isolated perfused rat livers

Chiaki Kamikado,1 Toshishige Shibamoto,4 Minoru Hongo,3 and Shozo Koyama2

1First Department of Surgery, Kagoshima University School of Medicine, Kagoshima 890-8520; 2Division 2, Department of Physiology, Shinshu University School of Medicine; 3Department of Cardiovascular Medicine, Shinshu University School of Health Sciences, Matsumoto 390-8621; and 4Division 2, Department of Physiology, Kanazawa Medical University, Uchinada 920-0293, Japan

Submitted 26 December 2002 ; accepted in final form 21 August 2003

We studied the effects of blood hematocrit (Hct), blood flow, or norepinephrine on segmental vascular resistances in isolated portally perfused rat livers. Total portal hepatic venous resistance (Rt) was assigned to the portal (Rpv), sinusoidal (Rsinus), and hepatic venous (Rhv) resistances using the portal occlusion (Ppo) and the hepatic venous occlusion (Phvo) pressures that were obtained during occlusion of the respective line. Four levels of Hct (30%, 20%, 10%, and 0%) were studied. Rpv comprises 44% of Rt, 37% of Rsinus, and 19% of Rhv in livers perfused at 30% Hct and portal venous pressure of 9.1 cmH2O. As Hct increased at a given blood flow, all three segmental vascular resistances of Rpv, Rsinus, and Rhv increased at flow >15 ml/min. As blood flow increased at a given Hct, only Rsinus increased without changes in Rpv or Rhv. Norepinephrine increased predominantly Rpv, and, to a smaller extent, Rsinus, but it did not affect Rhv. Finally, we estimated Ppo and Phvo from the double occlusion maneuver, which occluded simultaneously both the portal and hepatic venous lines. The regression line analysis revealed that Ppo and Phvo were identical with those measured by double occlusion. In conclusion, changes in blood Hct affect all three segmental vascular resistances, whereas changes in blood flow affect Rsinus, but not Rpv or Rhv. Norepinephrine increases mainly presinusoidal resistance. Ppo and Phvo can be obtained by the double occlusion method in isolated perfused rat livers.

blood viscosity; hepatic circulation; hepatic vascular occlusion methods


Address for reprint requests and other correspondence: T. Shibamoto, Dept. of Physiology, Division 2, Kanazawa Medical Univ., Uchinada 920-0293, Japan (E-mail: shibamo{at}kanazawa-med.ac.jp).






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