Vascular volume changes in the dog forelimb

¹ Department of Physiology, Medical College of Georgia, Augusta, Georgia

In an isolated dog forearm preparation perfusion pressure, venous pressure, and blood flow were determined. Blood flow and vascular volumes were estimated by arterial injection of red cells-Cr⁵¹ and albumin-I¹³¹. Measured blood flow agreed within ± 10% of that calculated from the indicator dilution. Vascular volume changes were determined from changes in limb weight. Measurements were made 1) during the control state, 2) during vasodilation with acetylcholine, and 3) after increasing the flow rate. The red cell-Cr⁵¹ volume averaged significantly less than that measured by the albumin-I¹³¹ at all three stages of the experiment. The ratio of the volumes (RBC-Cr⁵¹/albumin-I¹³¹) increased from 0.84 at the control to 0.93 in the dilated bed with elevated flow. Following vasodilation, the change in volume determined by weight change was significantly smaller than measured by the indicators. When flow was increased, the albumin-I¹³¹ measured a significantly smaller volume change than did the red cells-Cr⁵¹ or the weight. Three general types of time-concentration curves are described.

Key Words: indicator dilution • organ blood flow • red cell and plasma distribution • MTT technique • Cr⁵¹ red cells • I¹³¹ albumin • organ weight changes

Submitted on November 26, 1963