Role of endothelium-related mechanisms in the pathophysiology of renal ischemia/reperfusion in normal rabbits.

The present study addressed the effect of interventions aimed to increase NO in the setting of acute renal ischemia/reperfusion (I/R) in uninephrectomized rabbits. In the 60-minute post-I/R period, L-arginine+superoxide (O2.-) dismutase (SOD) synergistically improved the renal functional (69.4% versus 10.4% of the pre-I/R glomerular filtration rate with or without L-arginine+SOD, respectively; p < .01) and histological parameters (82.9% decrease of medullary congestion in L-arginine+SOD, P < .01 versus vehicle) and blocked the I/R-dependent neutrophil accumulation (89.3% reduction). In spite of these results over the short term, a second set of experiments disclosed that the protection by L-arginine+SOD was no longer present at 24 and 48 hours (plasma creatinine in vehicle-treated versus L-arginine+SOD-treated animals [mg/100 mL]: 24 hours after I/R, 9.4 +/- 1.9 versus 8.07 +/- 0.65; 48 hours after I/R, 11.6 +/- 3.6 versus 9.7 +/- 0.9; P = NS in all the cases). Additional experiments were conducted using a milder 30-minute ischemic model, which showed no significant functional or histological protection by using L-arginine+SOD. In conclusion, our experiments disclosed the following: (1) the critical importance of the interaction between NO and O2.- in the acute protective effect of L-arginine (this effect not only improved renal function and histology but also reduced neutrophil accumulation) and (2) the discordance existing between the immediate protection afforded by L-arginine+SOD and the lack of protection observed at 24 and 48 hours. This finding suggests that a punctual intervention on the NO system at the time of I/R is not sufficient to reduce renal damage over the long term.

Role of endothelin in the pathophysiology of renal ischemia-reperfusion in normal rabbits.

The present study addressed the acute effects of endothelin-1 on renal function and neutrophils accumulation in the setting of in vivo severe (60 min) acute ischemia/reperfusion. Ischemia/reperfusion decreased renal functional parameters and increased renal neutrophil accumulation and medullary congestion. All these parameters markedly improved with the intrarenal administration of anti-endothelin-1 antiserum. Comparatively, the intrarenal infusion of endothelin-1 decreased renal function and increased neutrophil accumulation. Abnormalities in renal histology were, however, less pronounced than with ischemia/ reperfusion. In experiments using rabbit isolated perfused kidneys, endothelin-1 induced the accumulation of labeled neutrophils. This accumulation was similar to that observed in kidneys obtained after 60 minutes of ischemia plus 60 minutes of reperfusion. Both endothelin and ischemia/ reperfusion effects were counteracted by an anti-endothelin antibody. In further in vitro studies, we found that endothelin-1-induced the expression of the CD18 antigens on the neutrophil surface. In subsequent experiments based on this effect of ET-1 on CD18 antigens, a blockade of both ischemia/reperfusion-induced and endothelin-1-induced neutrophil accumulation was obtained by infusion an anti-CD18 antibody. In conclusion, our experiments disclosed the critical role of endothelin-1 as a major promoter of early neutrophil accumulation after ischemia/reperfusion, which occurred through an integrin-mediated mechanism.

Aspirin-stimulated nitric oxide production by neutrophils after acute myocardial ischemia in rabbits.

BACKGROUND: In recent studies, it has been hypothesized that the protective anti-ischemic effects of aspirin outweigh the effects of inhibition of platelet thromboxane A2 synthesis. Recently, we have found that the antiaggregating effects of aspirin significantly affect nitric oxide (NO) generation by neutrophils. METHODS AND RESULTS: The present study used circulating neutrophils from myocardial ischemic rabbits to assess the effect of aspirin on the circulating neutrophil-derived NO production and, subsequently, on the modulation of platelet activation. Neutrophils were obtained after 60 minutes of coronary artery occlusion followed by 60 minutes of reperfusion. Sham-operated animals were used as controls. The results demonstrated that aspirin stimulated the production of NO by neutrophils obtained from both sham-operated rabbits and rabbits with myocardial ischemia. However, neutrophils isolated from animals with myocardial ischemia showed an enhanced ability to generate NO in the presence of aspirin. As a functional in vitro marker, we observed that neutrophils had a NO-dependent, platelet-antiactivating effect in the presence of aspirin. In the absence of aspirin, ischemic neutrophils did not modify platelet activation, even though they produced increased amounts of NO. An inhibitory role of superoxide anion on the neutrophil-related antiplatelet effect was suggested because superoxide dismutase induced significant platelet inhibition by myocardial ischemic neutrophils in the absence of aspirin. CONCLUSIONS: Our results show that myocardial ischemia/reperfusion stimulates production of NO by circulating neutrophils, an effect that was enhanced in the presence of aspirin. These results suggest a novel interpretation of the protective effect of aspirin on myocardial ischemia damage.

Effect of endothelin-1 on neutrophil adhesion to endothelial cells and perfused heart.

BACKGROUND: Based on recent evidence showing that endothelin-1 stimulates several activation mechanisms on neutrophils, the aim of the present study was to analyze the effects of endothelin-1 on neutrophil adhesion to endothelial cells and neutrophil accumulation in the heart. METHODS AND RESULTS: The experiments included (1) adhesion of 51Cr-labeled human neutrophils to bovine endothelial cells in culture both in the presence and absence of monoclonal antibodies against the alpha- and beta-subunits of integrins; (2) surface expression of the alpha- and beta-integrin antigens; (3) accumulation of 51Cr-labeled neutrophils on the isolated perfused rabbit heart; (4) in vivo accumulation of autologous neutrophils in the heart, as assessed by myeloperoxidase activity. Endothelin-1 stimulated neutrophil adhesion to endothelial cells (increase of 1 x 10(5) +/- 1 x 10(4) neutrophils per well). The endothelin-1-induced adhesion was blocked (83 +/- 6%) by the anti-CD18 antibody TS1/18 and by several anti-alpha-subunit antibodies. The expression of CD18 and CD11b on the neutrophil surface was also increased by endothelin-1. Endothelin-1 enhanced neutrophil accumulation in the isolated rabbit heart by 4.2 times throughout a TS1/18-inhibitable mechanism. Myeloperoxidase activity increased by 4.2 times in hearts infused in vivo with endothelin-1. CONCLUSIONS: Endothelin-1 stimulates neutrophil adhesion to endothelial cells by an effect on the expression of adhesive molecules on the neutrophil surface. Endothelin-1 stimulates neutrophil accumulation in vivo and in vitro in the heart. Antibodies against the integrin complex block the endothelin-1-dependent neutrophil adhesion. These findings have potential importance in the pathophysiology of endothelin-1-increased states.

Renal and systemic effects of aminoacids administered separately: comparison between L-arginine and non-nitric oxide donor aminoacids.

The present study examined the mechanisms of the renal effect of the NO-donor aminoacid, L-Arg and different non-NO-donor aminoacids, namely L-Asn, L-Ala, L-Gly L-Gln administered separately. In conscious, unrestricted Wistar rats, a bolus of L-Arg produced a short-lasting decrease in mean arterial pressure. No variations in mean arterial pressure were found with either L-Gly, L-Asn, L-Ala or L-Gln. This effect of L-Arg was inhibited by NwNLA, methylene blue and atropine and not affected by meclofenamate. Simultaneously, a dose-response diuretic and natriuretic effect was observed with all the aminoacids. In further experiments with L-Arg and L-Gly, this effect was associated with increased glomerular filtration rate, renal plasma flow, fractional sodium and free water excretion and urinary cyclic guanosine monophosphate. These effects of L-Arg and L-Gly were inhibited by NwNLA. On the contrary, no inhibition by NwNLA was detected on the diuretic, natriuretic and renal hemodynamic effects of L-Gln, and the diuretic and natriuretic effects of L-Asn or L-Ala. Our results show that all the assayed aminoacids were endowed of diuretic and natriuretic capabilities. Such effects were apparently related with a NO-mediated mechanism in the case of L-Arg and L-Gly, but not in the case of L-Gln, L-Asn or L-Ala, therefore suggesting that more than one mechanism is involved in the renal effect of the different aminoacids. Simultaneously, only L-Arg produced a NO-, cyclic guanosine monophosphate-dependent hypotensive effect, which was not shared by the other assayed aminoacids.

Intravascular and interstitial fluid dynamics in rats treated with minoxidil.

Edema is a major complication of vasodilatory therapy. However, the pathophysiologic mechanisms leading to the formation of vasodilator-mediated edema are insufficiently understood. The present study therefore examined the effect of the chronic administration of the potent arteriolar vasodilator, minoxidil (Mx), on extracellular fluid dynamics in rats. Extracellular volume (ECV), plasma volume (PV), interstitial fluid volume (IV), arterial pressure (AP), and interstitial fluid pressure (IP) were measured in rats treated for 10 days with Mx (1.5 mg/kg/day) and in control animals. In addition to a decreased AP, Mx-treated animals had diminished water and sodium excretion. ECV, PV, and IV and plasma renin concentration (PRC) were also increased in the Mx-treated rats. IP, which was subatmospheric in control rats (-2.6 +/- 0.04 mm Hg), was near zero in Mx-treated animals (-0.2 +/- 0.02 mm Hg, p less than 0.05). Saline ECV expansion (20 min, Ringer infusion, 3% body weight) or rat albumin injection (300 mg/2 ml) induced similar changes in the volume of the extracellular fluid compartments in both groups. However, changes in IP were blunted in Mx-treated rats. These results, therefore, show that Mx-treated rats have changes in interstitial fluid dynamics prior to any macroscopic evidence of edema accumulation. These alterations in the extracellular compartment dynamics may be a consequence of the sustained arteriolar vasodilation induced by Mx.

[Acute infantile traumatic pancreatitis (author's transl)]. / Pancreatitis aguda traumática infantil.

Authors present a case of acute infantile traumatic pancreatitis secondary to a stenosing duodenal hematoma, exceptional etiologic mechanism. Taking into consideration this case, they review some of the diagnostic aspects and their treatment, emphazysing the need of surgical approach as a correct diagnostic treatment.