[Capillary permeability and macromolecular exchange with special reference to structure of microvascular walls].
This paper reviews current concepts of capillary permeability of lipophilic and hydrophilic solutes, and macromolecular exchange across the microcirculation with special reference to structure of microvascular walls. Lipophilic and hydrophilic solutes must be differentiated because the barriers encountered by these classes of substances in the capillary walls are very different. Most hydrophilic solutes are mainly restricted to the paracellular pathway, whereas lipophilic solutes use the cellular pathway. Toward the end of the last century, Starling proposed that fluid flow through capillary walls is passive. He suggested that the energy for transcapillary fluid flow lay in the differences in hydrostatic and osmotic pressures between the circulating plasma and the tissues. It has been established that most proteins present in plasma cross capillary and venular walls, diffuse through the tissues, and return to the plasma via the lymphatic system. Thus both small and large pores are necessary to describe the movement of large molecules across the capillary and venular walls.
Ohhashi
Toshio
T
Department of Physiology, Shinshu University School of Medicine.
D000818:Animals; D002196:Capillaries / Q000648:ultrastructure*; D002199:Capillary Permeability / Q000502:physiology*; D006801:Humans; D008833:Microcirculation / Q000502:physiology*; D008954:Models, Biological