MECHANISM OF HISTAMINE-INDUCED TRANSCAPPILLARY FLUID MOVEMENT

This study was designed to determine the direct effect of histamine on capillary membrane permeability and pre- and post-capillary resistances. Ten experiments were carried out on isolated forelimbs of dogs perfused with blood oxygenated by a Starling heart-lung preparation. Permeability was determined by measuring the isogravimetric capillary pressure (Pci) using a modification of the Pappenheimer and Soto-Rivera technique. Histamine was administered by intraarterial infusion in increasing doses, ranging from 2.7 to 68 μg/min. Results show a significant, dose dependent fall of mean Pci from 10.7 to 7.7 mm Hg when histamine was given in a dosage of 6.8 μg/min or higher. Pre-capillary resistance fell with each histamine dose used in these experiments. No significant change of the post-capillary resistance occurred, except during infusion of histamine at doses between 27 and 68 μg/min. It is suggested that histamine increases the permeability of the capillaries due to a direct action on the capillary membrane. Additional increases in hydrostatic capillary pressure may contribute to net capillary filtration induced by histamine. © 1969 Springer-Verlag.