Effects of catecholamines on splenic blood flow in the cat

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Abstract
Electromagnetic flowmeters were used to determine the effects of local rapid intra-arterial injections of catecholamines on splenic inflow and outflow in anesthetized cats. The control flows showed oscillations with a period of 30-50 sec. with arterial flow leading venous flow by 8[long dash]10 sec. Intra-arterial isoproterenol greatly increased the amplitude of these oscillations but did not alter this frequency or the arterial and venous phase relationship. Small doses of epinephrine initially increased arterial inflow. Larger doses of epinephrine and all doses of norepinephrine initially decreased inflow and simultaneously increased outflow. These changes were of brief duration and were commonly followed by a more prolonged increase of splenic inflow and outflow with an increase in the amplitude of the flow oscillations. After beta adrenergic blockade isoproterenol produced no change in splenic flow and the inflow increases produced by epinephrine were reversed. The venous outflow increases were reduced. Beta adrenergic receptor stimulation is a prominent feature in the responses of the cat''s splenic circulation to catecholamines but the ''emptying mechanism'' of the spleen does not involve beta receptors.

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