Pulmonary edema induced by angiotensin II in rats

Angiotensin peptides attenuate platelet-activating factor-induced inflammatory activity in rats

Angiotensin (Ang)--a peptide that is part of the renin-angiotensin system-induces vasoconstriction and a subsequent increase in blood pressure; Ang peptides, especially AngII, can also act as potent pro-inflammatory mediators. Platelet-activating factor (PAF) is a potent phospholipid mediator that is implicated in many inflammatory diseases. In this study, we investigated the effects of Ang peptides (AngII, AngIII, and AngIV) on PAF-induced inflammatory activity. In experiments using a rat hind-paw oedema model, AngII markedly and dose-dependently attenuated the paw oedema induced by PAF. The inhibitory effects of AngIII and AngIV on PAF-induced paw oedema were lower than that of AngII. Two Ang receptors, the AT1 and AT2 receptors, did not affect the AngII-mediated attenuation of PAF-induced paw oedema. Moreover, intrinsic tyrosine fluorescence studies demonstrated that AngII, AngIII, and AngIV interact with PAF, and that their affinities were closely correlated with their inhibitory effects on PAF-induced rat paw oedema. Also, AngII interacted with metabolite/precursor of PAF (lyso-PAF), and an oxidized phospholipid, 1-palmitoyl-2-(5'-oxo-valeroyl)-sn-glycero-3-phosphocholine (POVPC), which bears a marked structural resemblance to PAF. Furthermore, POVPC dose-dependently inhibited AngII-mediated attenuation of PAF-induced paw oedema. These results suggest that Ang peptides can attenuate PAF-induced inflammatory activity through binding to PAF and lyso-PAF in rats. Therefore, Ang peptides may be closely involved in the regulation of many inflammatory diseases caused by PAF.

Rapid Improvement of Acute Pulmonary Edema with Angiotensin Converting Enzyme Inhibitor under Hemodialysis in a Patient with Renovascular Disease

A 71-year-old man with bilateral renovascular disease was admitted to Hamamatsu University hospital because of appetite loss and acute shortness of breath due to acute pulmonary edema (APE) with accelerated hypertension and renal failure. Hypertension and APE were controlled by an angiotensin converting enzyme inhibitor (ACEI) and four sessions of hemodialysis with reduction of 1.8 kg bodyweight. Renal function was later stabilized and the patient required no ACEI or hemodialysis. A trial of right renal angioplasty 1 month after admission failed and renal function deteriorated (serum creatinine 7.1 mg/dL) with accelerated hypertension, gain of bodyweight and APE. Even after four sessions of hemodialysis with adequate reduction of bodyweight, APE was not controlled, but it rapidly improved after administration of an ACEI, without major bodyweight change. As no apparent cardiac dysfunction was evident, APE might have been caused by a direct action of angiotensin II on hyperpermeability in pulmonary capillaries. Blocking of angiotensin II should be considered in such patients even after introduction of hemodialysis.

Pulmonary edema induced by angiotensin I in rats

This study was performed to demonstrate an experimental procedure of pulmonary edema induced by angiotensin I (AT I) in rats and to elucidate the mechanism of hemodynamic pulmonary edema. In the previous pilot study, 20 microg/kg of AT I was found to be an adequate dose for inducing pulmonary edema. To elucidate the mechanism of AT I pulmonary edema and protective measures against it, we observed the effects of captopril (CAP, 5 and 10 mg/kg), an angiotensin converting enzyme inhibitor; losartan (LOS, 10 mg/kg), an angiotensin II (AT II)-receptor antagonist; and phentolamine (PHE, 10 mg/kg), an alpha-adrenergic receptor blocker, on AT I-induced pulmonary edema in rats. Similarly, we also observed the effects of CAP (10 and 20 mg/kg) on pulmonary edema induced by 25 microg/kg of adrenaline (ADR) in rats. The development of AT I-induced pulmonary edema was significantly suppressed by CAP and LOS, but was unaffected by PHE. In contrast, the development of ADR-induced pulmonary edema was not suppressed by CAP. These results suggest that AT I-induced pulmonary edema is developed via the AT II and a specific AT II-receptor, without the indirect action of adrenaline.

Angiotensin II-Induced Pulmonary Edema in a Rabbit Model

Effect of minaprine on hypoxia- or hypoxia/hypoglycemia (ischemia)-induced impairment of 2-deoxyglucose (2DG) uptake by rat hippocampal slices was evaluated. Since minaprine was found to possess both a stimulating effect on acetylcholine release and a blocking effect on 5-HT2 receptors, the improving effect of minaprine on impaired 2DG uptake was compared to the findings obtained with oxotremorine, ketanserin and pentobarbital. Hippocampal slices were exposed to 20-min ischemia, and then these slices were returned to oxygenated and glucose-containing buffer for 6 hr. Ischemia reduced 30 mM KCl-induced 2DG uptake by the hippocampus. Pretreatment with minaprine, oxotremorine, pentobarbital and ketanserin attenuated the ischemia-induced decline of 2DG uptake. In addition, minaprine, oxotremorine and pentobarbital relatively recovered the increase of 2DG uptake in the hippocampal slices under hypoxia for 45 min. The present results suggest that minaprine exerts a neuroprotective action against ischemia-induced deficit of energy metabolism in vitro.