Vascular volume changes resulting from vasodilation of the dog forelimb

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

In an isolated dog forelimb preparation, perfusion pressure, venous outflow pressure, and blood flow were determined. Vascular volume changes were estimated by arterial injections of red cells-Cr⁵¹ and albumin-I¹³¹ and by changes in limb weight. Measurement of the recovery of the above two indicators as well as the diffusible indicator Rb⁸⁶Cl was made. Net capillary filtration of fluid was also determined from changes in weight of the limb. Measurements were made: 1) under control conditions, 2) during vasodilation with acetylcholine, 3) following 25 ml/min increment in flow rate through the dilated bed, 4) following another 25 ml/min increment in flow rate. Following vasodilation, the increase in vascular volume determined by weight change was significantly smaller than that measured by the indicators, recovery of Rb³⁶Cl was significantly less than during the control, and the net transfer of fluid was increased. Each time flow was increased, the red cells-Cr⁵¹, albumin-I¹³¹, and weighing device measured similar increases in vascular volume.

Key Words: regional blood flow • indicator dilution • acetylcholine • net capillary filtration • weight changes • diffusible indicator

Submitted on December 7, 1964