The Effect of Serotonin and Transcapillary Pressure on the Capillary Permeability in the rete mirabile of the Eel (Anguilla vulgaris L.)

Abstract

Measurements of transcapillary exchange of high-molecular dextrans, K+ and THO in the rete mirabile of eel (Anguilla vulgaris L.) have been made under steady-state conditions while the transcapillary pressure was varied and pharmaca added to the perfusates. Raising the transcapillary input pressure increased the exchange of dextrans and K+ but lowered that of THO. Histamine and ouabain had no effect on the transcapillary exchange of the test molecules. The highest dose (100 mug/ml) of serotonin reversibly increased the capillary permeability of D-75 000, K+ and THO while the medium dose (50 mug/ml) only raised the transcapillary exchange of K+ and THO. The lowest dose (10 mug/ml) had no permeability effect. Our main conclusion is that serotonin reversibly increases the area of the intercellular pores by affecting the capillary wall directly.