Demonstration of pulmonary vascular perfusion by electron and light microscopy.
To estimate the fraction of dense pulmonary capillary network that is perfused under physiological conditions, we developed a new method for the demonstration of in vivo capillary perfusion by light and electron microscopy. Blood plasma was labeled by 8-nm colloidal gold particles coated with rabbit serum albumin. In anesthetized rabbits, 4-5 ml of this tracer were injected into the right atrium. Two and 15 min later, the circulation was interrupted by a snare around the heart, and the lung was fixed by instillation with glutaraldehyde. Gold particles were found in the plasma space of alveolar capillaries as well as in other organs. A random sample of thin sections studied by electron microscopy revealed that the entire capillary bed of the lung was perfused at least with plasma within 2 min after tracer infusion. Light microscopy of silver-enhanced sections showed areas with different staining intensities but no obviously unperfused capillaries. The concept of capillary recruitment, which would require a significant fraction of capillaries unperfused at rest, may have to be reassessed to consider time factors as well as the two-phase nature of blood; red blood cells and plasma may take different paths.
König
M F
MF
Institute of Anatomy, University of Berne, Switzerland.
Lucocq
J M
JM
Weibel
E R
ER
D000818:Animals; D002196:Capillaries / Q000502:physiology; D004705:Endocytosis / Q000502:physiology; D006046:Gold / Q000097:blood; D008168:Lung / Q000033:anatomy & histology / Q000098:blood supply* / Q000648:ultrastructure; D008176:Lung Volume Measurements; D008854:Microscopy, Electron; D008863:Microspheres; D016612:Paraffin Embedding; D011817:Rabbits; D012709:Serum Albumin; D013056:Spectrophotometry, Ultraviolet
D012709:Serum Albumin; D006046:Gold