| Popis: |
After congestive heart failure (CHF), lung endothelial permeability responses to a number of perturbations, including acute barotrauma, angiotensin II, and thapsigargin are blunted. Our hypothesis was that similar attenuation of permeability responses occurs in peripheral vascular beds after CHF. We compared peripheral microvascular permeability responses to the autacoid histamine in control dogs and in dogs paced to heart failure (245 bpm for approximately 36 days). Since catecholamines attenuate autacoid-induced increases in microvascular permeability in skin and muscle in normal animals, we also tested whether the known elevation in catecholamines in CHF was involved in any downregulation of permeability responses in this group.Control and paced dogs were anesthetized, intubated, and ventilated, and a hindpaw lymphatic cannulated. The reflection coefficient for total proteins (sigma) was measured at baseline and during one-hour, local intra-arterial histamine infusion.In controls, sigma fell from 0.83 +/- 0.02 to 0.73 +/- 0.04 after histamine (p0.05), while in the paced group sigma was no different from that at baseline (0.77 +/- 0.02). To test whether this difference was due to endogenous catecholamines, dogs were pretreated with propranolol (controls only) or the specific beta 2-antagonist ICI 118,551 prior to histamine infusion. After beta-blockade, histamine significantly reduced sigma in both control (0.83 +/- 0.01 to 0.55 +/- 0.05) and paced (0.83 +/- 0.01 to 0.57 +/- 0.07) groups (p0.05).We conclude that endogenous catecholamines, acting via beta 2-adrenergic receptors, attenuate the permeability response to histamine in pacing-induced heart failure. |
