Erythrocyte uptake by the dog's spleen during splenic venous pressure elevation

The spleens of chloralose-urethane anaesthetized dogs were isolated, placed in a plethysmograph and perfused at constant arterial pressure from a cannulated femoral artery. Splenic venous pressure (PV) was elevated by between 2.5 and 20 cm H2O: it caused pressure-dependent increases in spleen volume of up to 98 +/- 12 ml/100 g spleen weight. The increase in spleen volume could be separated into an initial phase associated with passive distension of capacitance vessels (Phase-1) followed by a more continuous increase in spleen volume (Phase-2). We used techniques designed to distinguish these components of the volume response to PV elevation, and found Phase-2 rates of increase in spleen volume of 5--10 ml min-1 mm Hg-1 100 g-1 expressed in terms of PV elevation and terminal, drained and trimmed spleen weight. Splenic venous haematocrit determination showed selective sequestration of RBCs during the Phase-2 volume response to PV elevation which was related to the extent of the PV elevation. Both the Phase-2 volume response and the haematocrit changes were reduced by splenic nerve stimulation or i.a. infusions of adrenaline but were unaffected by i.a. infusions of bradykinin.