Effect of Infusions of Osmotically Active Substances on Muscle Blood Flow and Systemic Blood Pressure

To investigate further the action of alterations in plasma osmolarity, the flow through the gastrocnemius-plantaris muscle group and the whole hind leg was measured during close intra-arterial infusions of solutions containing osmotically active substances. The transient and steady-state responses showed dilatation during infusion of hypermolal solutions. Some of the transient responses were difficult to explain. Intravenous infusions of hyperosmolal solutions caused an increase in cardiac output, arterial blood pressure, and right atrial pressure and a decrease in resistance to flow through the hind leg. These responses were probably due to constriction of the venous capacitance vessels and dilatation of the precapillary resistance vessels and were caused by some unknown mechanism.