Transcapillary protein leakage and fluid movement: Effect of venous pressure

Abstract

The effect of elevating venous pressure ( ΔP v) on the transcapillary escape of albumin ( Q T) in control and papverinized gracilis muscles perfused at constant flow was determined by means of direct monitoring of the rate of accumulation of tissue 125I-labeled albumin radioactivity. Simultaneously, transcapillary fluid movement (FM) was assessed volumetrically. Under control isovolumetric conditions, Q T = 2.25 mg/min · 100 g. In addition to causing an FM of 0.03 ml/min · 100 g · mm Hg, increasing P v enhanced Q T by 0.06 mg/min · 100 g · mm Hg. Papverinization itself decreased Q T to 2.0 mg/min · 100 g and affected FM only slightly. However, the superposition of P v elevation caused a FM of 0.008 ml/min · 100 g · mm Hg and resulted in Q T increasing by 0.29 mg/min · 100 g · mm Hg. The results of this study indicate that Q T is sensitive to changes in microvascular hemodynamics, and thus changes in microvascular pressure may affect FM in two ways, first by increasing the transcapillary pressure gradient and second by augmenting Q T which may superimpose an oncotic adjunct to FM.