Control of transcapillary water movement by vasoactive agents

Experiments were performed to demonstrate that papaverine can increase capillary filtration coefficient, CFC, and to investigate whether this increase could be reversed by isoproterenol, norepinephrine and plasma. The study used the isolated cat hindlimb, perfused at constant flow with a recirculated blood-albumin solution. It was observed that papaverine increased CFC in a dose-dependent manner, and that this effect could be reversed by isoproterenol and norepinephrine. Norepinephrine reduced CFC even in the presence of phentolamine. Plasma, previously shown to reduce CFC when papaverine was present, was shown to have no such effect when papaverine was absent. It is argued that the CFC changes are best explained by changes in the hydraulic conductivity of the exchange vessels, rather than through changes in the perfused surface area, and that the CFC changes are similar to the permeability changes caused by inflammatory mediators and catecholamines observed by others.