Transient effects of histamine on microvascular fluid movement

Abstract

There have been many reports on the effect of local intraarterial (IA) histamine on the capillary filtration coefficient (CFC) and the isogravimetric capillary pressure (Pci). CFC has been reported to increase during infusion of this agent but the reported magnitude of increase is widely variable. Similarly, histamine has been reported to cause little change or a decrease in Pci. It was felt that histamine may have some time-dependent effect on CFC and Pci and that this might explain, at least in part, the variation. To test this hypothesis, CFC and Pci were measured in the isolated, denervated canine forelimb at timed intervals during infusion of local IA histamine (12 μg base/min). Also, lymph and plasma samples were collected and lymph flow and lymph and plasma protein concentration were determined. Permeability-surface area (PS) product ratios were estimated from steady-state lymph data. Propranolol (2–3 mg/kg iv priming dose and 123 μg/min locally) was administered throughout the experiment to inhibit possible catecholamine-mediated inhibition of histamine-induced increases in fluid and protein efflux. CFC averaged 0,013 ml/min/mm Hg/100 g at control and increased to 0.040 and 0.048 after 5 and 10 min of histamine, respectively. Subsequent CFC determinations were not different from control. Pci was not altered by histamine at this dose. The estimated PS ratio was 43. Control experiments were conducted in which propranolol and the saline vehicle were infused. No change in any variable in the control group occurred with time. These data indicate that the effect of histamine on the small-pore system, as reflected by changes in CFC, is highly transient.