Effect of the spleen in norepinephrine action on blood volumes of the dog

¹ Department of Physiology, University of Louisville School of Medicine, Louisville, Kentucky

In intact and splenectomized dogs the plasma and cell volumes were measured simultaneously by means of Risa and P³²-tagged erythrocytes. Two measurements were made in each dog; first during a control period and second during a constant norepinephrine infusion or, in some dogs in the splenectomized group, after neurogenic vasoconstriction. Average values were as follows: In the intact group norepinephrine produced a decrease in the F factor_cells (0.884 to 0.820), an increase in the excess plasma volume (9.7 to 14.8 ml/kg), and a small decrease in total plasma volume (50.1 to 48.5 ml/kg). In the splenectomized group norepinephrine or neurogenic vasoconstriction caused a rise in the F_cells factor (0.806 to 0.858), a decrease in the excess plasma (13.8 to 9.3 ml/kg), and a more marked fall in the total plasma volume (44.9 to 39.6 ml/kg). A norepinephrine-induced redistribution of splenic blood in the intact animals could not quantitatively explain the observed changes. It was concluded that the ejection of splenic blood modifies antagonistically the effects of norepinephrine on the plasma and excess plasma volumes by counteracting the vasoconstrictor effect of norepinephrine on vessels small enough to contain plasma-rich blood.