Increased Transcapillary Escape Rate of Albumin, IgG, and IgM during Angiotensin-II-Induced Hypertension in Man

Abstract

The transcapillary escape from plasma to the interstitial space of albumin and two plasma globulins, IgG and IgM, was studied in man during angiotensin II infusion causing an average increase of 42% in the mean arterial blood pressure. The intravascular mass of each protein was determined before and after 90 minutes’ hypertension, in order to obtain a measure of the change in the transcapillary escape rate of each protein. The transcapillary escape rate of albumin was also determined by use of radioiodinated albumin. During the hypertensive period the transcapillary escape rate for all 3 proteins increased. The relative increase was much more pronounced for IgM and IgG (+170%) than for albumin (+75%). The ratio between the transcapillary escape rate and the free diffusion coefficient increased with increasing molecular size, a finding which cannot be explained by simple diffusion. The central and peripheral venous pressure increased and the plasma volume decreased during the angiotensin II infusion period. Our results can best be explained by increased filtration through enlarged pores between the endothelial cells of the microvasculature, owing to the arterial pressure elevation caused by the angiotensin II infusion.

Key Words:

• Acute hypertension
• angiotensin II
• diffusion
• filtration
• interendothelial pores
• microvascular escape of plasma proteins
• plasma volume
• vesicles