Effects of histamine and histamine antagonists on intestinal capillary permeability.
Steady-state lymph flow, blood flow, and lymph and plasma total protein concentration were measured in an autoperfused cat ileum preparation during the continuous infusion of histamine at venous pressures of 0, 10, 20, and 30 mmHg. The capillary osmotic reflection coefficients for total proteins and each protein fraction were estimated. In addition, the ileum was pretreated with an H1-receptor antagonist (diphenhydramine) or with an H2-receptor antagonist (cimetidine). The results suggest that histamine selectively increases the ileal vascular permeability to plasma proteins of a molecular radius up to 96 A. The H1-receptor antagonist did not alter the histamine-induced permeability changes but did block the observed initial vasodilation. The H2-receptor antagonist significantly reduced the permeability changes associated with histamine while having only a slight effect on the initial vasodilation. It is concluded that the activation of H1-receptors is predominantly associated with the initial vasodilation, whereas the H2-receptors are predominantly associated with permeability.
D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D002199:Capillary Permeability / Q000187:drug effects*; D002415:Cats; D002927:Cimetidine / Q000494:pharmacology; D004155:Diphenhydramine / Q000494:pharmacology; D005260:Female; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology*; D007422:Intestines / Q000098:blood supply*; D008208:Lymphatic System / Q000187:drug effects / Q000502:physiology; D009997:Osmotic Pressure; D011969:Receptors, Histamine H1 / Q000502:physiology; D011970:Receptors, Histamine H2 / Q000502:physiology; D012039:Regional Blood Flow / Q000187:drug effects; D014690:Venous Pressure
D001798:Blood Proteins; D006633:Histamine Antagonists; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D002927:Cimetidine; D006632:Histamine; D004155:Diphenhydramine