Nitric oxide synthase induction by ouabain in vascular smooth muscle cells from normotensive and hypertensive rats.

OBJECTIVE: To investigate the effect of ouabain on inducible nitric oxide synthase (iNOS) activity and expression in cytokine-stimulated vascular smooth muscle cells (VSMC) from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). METHODS: VSMC were treated for 24 h and afterwards, nitric oxide (NO) release was determined by the production of nitrite, a stable metabolite of NO. Activity of iNOS was measured by the conversion of [3H]-L-arginine to [3H]-L-citrulline and iNOS protein expression by Western blotting. RESULTS: Ouabain (0.01-1 mmol/l) further enhanced interleukin-1beta (II-1beta)-induced nitrite production by WKY and SHR VSMC, although a more pronounced effect was observed in SHR cells (maximum response 52.1 +/- 5.2 and 71.2 +/- 6.4% of 11-1beta effect in WKY and SHR cells, respectively). Such response on NO release was mimicked by the calcium ionophore A 23187 (0.01-1 micromol/l) and abolished by the voltage-operated calcium channels (VOCC) nifedipine (0.1 micromol/l). Expression of iNOS showed that ouabain increased the synthesis of the enzyme in WKY and SHR VSMC stimulated with II-1beta, and this effect was higher in SHR cells. The increased iNOS expression was significantly reduced by nifedipine. CONCLUSIONS: Ouabain stimulation of iNOS expression and activity in II-1beta-stimulated VSMCs from WKY rats and SHR seems to be related to increased intracellular calcium influx through VOCC. The more pronounced effect observed in SHR VSMC could be explained by an altered calcium entry in the hypertensive strain.

Cell volume and ionic transport systems after cold preservation of coronary endothelial cells.

BACKGROUND: Hypothermia-induced changes in cell volume and ionic transport systems of coronary endothelial cells may play a role in the development of coronary artery disease in cardiac transplant recipients. METHODS: Coronary endothelial cells were incubated in University of Wisconsin solution or culture control medium for up to 48 hours at 4 degrees C. Parallel control cultures were incubated at 37 degrees C. Na/K-ATPase and Na/K/Cl cotransport activities were determined as ouabain- and furosemide-sensitive 86Rb+ uptake, respectively. Cell volume changes and cell death were analyzed by a FACScan flow cytometer and the release of lactate dehydrogenase, respectively. RESULTS: Coronary endothelial cells stored in University of Wisconsin solution up to 6 hours showed an increased Na/K-ATPase activity compared to control cells, whereas no changes were observed in Na/K/Cl cotransport activity or cell volume. Long-term preservation (24 and 48 hours) was associated with a partial loss of cell viability, as demonstrated by lactate dehydrogenase release, and dramatic alterations in ionic transport system activities. CONCLUSIONS: University of Wisconsin solution seems to prevent coronary endothelial cells Na/K/Cl cotransport activity changes during cold preservation, which could alter cell volume regulation and cause cell injury.

Effect of ouabain in pressurized middle cerebral arteries from normotensive and hypertensive rats.

The aim of the present study was to assess the ability of ouabain to induce vasomotor responses and interfere with the myogenic tone in isolated segments of middle cerebral arteries from male Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) subjected to different pressures and no-flow conditions using a pressure myograph. At 60 mmHg, ouabain (1 nM-1 mM) caused relaxations at concentrations of 10 microM and up in segments from WKY while 1 nM ouabain produced a relaxation that was unaltered by the remaining concentrations in SHR segments. The relaxations were higher in SHR than in WKY arteries. Endothelium removal practically abolished the relaxation in arteries from both strains, whereas 10 microM L-NAME (an inhibitor of nitric oxide synthase) had no effect. When arteries were pressurized from 20-120 mmHg, myogenic activity developed in 3 out of 10 WKY arteries while SHR arteries did not show myogenic tone. Endothelium removal did not alter the effects of pressure increase in both strains, and incubation of segments in a Ca(2+)-free medium to abolish myogenic tone, shifted the pressure-response curve of WKY segments to the left; pressure-response curves from SHR were not modified. Although ouabain (0.1 mM) did not alter the pressure-response curve from WKY segments, curves obtained from SHR were shifted to the left. These results suggest that: 1) ouabain produces vasodilation in pressurized middle cerebral arteries of WKY and SHR which is positively modulated by an endothelial factor distinct from nitric oxide; and 2) only WKY arteries develop myogenic activity while the diameter of SHR arteries is passively enhanced with increases in intraluminal pressure. This passive increase is facilitated by ouabain. Therefore, hypertension modifies the mechanical properties of cerebral arteries resulting in a loss in the capacity for autoregulation.

Different sensitivity of isoprenaline-induced responses in ventricular muscle to sodium nitroprusside in normotensive and spontaneously hypertensive rats.

1. The aim of the present work was to study the possible modulatory role of nitric oxide (NO) on the positive inotropic effect induced by the beta-adrenoceptor agonist isoprenaline in myocardial contractility, and whether this modulation is altered by hypertension. 2. The study was performed using right ventricular strips from the hearts of 6-month-old male Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The contractile force of electrically-stimulated ventricular strips was measured by a force-displacement transducer. 3. Isoprenaline (from 10 nmol l(-1) to 10 micromol l(-1)) induced a concentration-dependent increase in cardiac contractility in strips from both rat strains. This positive inotropic effect to isoprenaline was reduced by the NO donor sodium nitroprusside (SNP, 0.1 mmol l(-1)) in muscles from WKY rats and slightly increased in those from SHR. The SNP-induced increase in strips from SHR was abolished by superoxide dismutase (100 U ml(-1)). 4. N(G)-nitro-arginine-methyl ester (L-NAME, 0.1 mmol l(-1)) and 1H-[1,2,4]oxadiazolo[4,3]-quinoxalin-1-one (ODQ, 10 micromol l(-1)), respective inhibitors of NO synthase and guanylate cyclase, increased the response to isoprenaline in muscles from WKY rats, whereas it was unaltered in strips from SHR. 5. In strips from WKY rats, the combination of ODQ and SNP produced an increase in the response elicited by isoprenaline, which was similar to that observed with ODQ or L-NAME. 8-Br-cyclicGMP (8-Br-cGMP, 0.1 mmol l(-1)), a permeable and structural cGMP analogue, decreased the effect induced by isoprenaline only in muscles from WKY rats. 6. These results suggest that the positive inotropic response to isoprenaline in ventricular strips from WKY rats is negatively modulated by NO, and positively by superoxide anions in those from SHR. The lack of a modulatory response to NO in ventricular strips from SHR is probably a result of an alteration of mechanisms in NO-signalling pathway downstream of cGMP formation in SHR hearts.

Hypothermic storage of coronary endothelial cells reduces nitric oxide synthase activity and expression.

Preservation with University of Wisconsin (UW) solution has been implicated in coronary artery endothelial damage and loss of endothelium-dependent vasodilatation. Therefore, the objective of this study was to investigate the effect of this solution on basal nitric oxide (NO) release from porcine coronary endothelial cells (CEC). Cultures were exposed to cold (4 degrees C) storage in UW solution for 6, 8 and 12 h. Parallel cultures were incubated with control medium at 37 degrees C. After treatment, NO release was evaluated by nitrite production, a stable metabolite of NO. Activity of the constitutive endothelial nitric oxide synthase (eNOS) was measured by the conversion [3H]-l-arginine to [3H]-l-citrulline and eNOS protein expression by Western blotting. Nitrite production by control cells was augmented with increasing times of incubation, whereas no change was observed in those cultures preserved with UW solution. Activity of eNOS was significantly decreased compared to the respective control group by cold storage of cells for longer periods than 6 h. Such decrease was correlated with a diminished eNOS protein expression in CEC preserved with UW solution after 8- and 12-h storage. These results suggest that prolonged hypothermic storage of CEC with UW solution does not preserve basal NO release because of a certain loss of eNOS protein, which may contribute to the reported injury of heart transplants after long-term preservation.

Changes of cardiac calcium homeostasis in spontaneously hypertensive rats.

The aim of the present study was to assess the alterations in cardiac Ca2+ homeostasis induced by hypertension using electrically paced right ventricular strips from Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). 2 Basal contractile force was higher in SHR than in WKY. Similarly, the beta-adrenoceptor agonist isoprenaline (10 nM-10 microM) induced a concentration-dependent positive inotropic effect that was higher in SHR than in WKY, which was in turn inhibited by the beta-adrenoceptor antagonist propranolol (1 microM) in both strains. 3 Preincubation of strips with the L-type Ca2+ channel blockers, nifedipine (1 microM) or verapamil (10 microM), markedly inhibited the isoprenaline response, the inhibition being higher in SHR than in WKY. However, this inhibition was minor by the T-type Ca2+ channel blocker mibefradil (10 microM). 4 Bay K 8644 (10 nM-10 microM), a L-type Ca2+ channel activator induced a concentration-dependent positive inotropic effect, that was greater in SHR than WKY. 5 Nifedipine and verapamil (both 0.1 nM-10 microM) inhibited in a concentration-dependent way the inotropic effect induced by 0.3 microM isoprenaline or 1 microM Bay K 8644. The inhibition was higher in SHR than in WKY. Mibefradil (0.1 nM-10 microM) only clearly inhibited the isoprenaline and Bay K 8644 inotropic effects at 10 microM in both strains. 6 The inhibitor of the sarcoplasmic reticulum Ca2+ release, ryanodine (10 nM-10 microM), was a more effective depressor of isoprenaline-induced response in SHR than in WKY. 7 These results suggest that cardiac Ca2+ homeostasis in SHR ventricular strips is altered compared with those of WKY, showing an increased Ca2+ entry through L-type Ca2+ channels and release from sarcoplasmic reticulum; the participation of T-type Ca2+ channels are irrelevant in this tissue.

Síndrome antifosfolípido primario y gestación: tratamiento con AAS y heparina de bajo peso molecular / Primary antiphospholipid syndrome and pregnancy: treatment with ASA and low-molecular-weight heparin

El Síndrome Antifosfolípido (SAF) Primario se manifiesta por la aparición de trombosis arteriales y/o venosas, pérdidas fetales recurrentes y/o trombopenia, en presencia de anticuerpos antifosfolípidos, y sin que exista ninguna enfermedad subyacente de naturaleza autoinmune, preferentemente Lupus Eritematoso Sistémico (LES). Desde el punto de vista obstétrico puede asociarse a graves complicaciones materno-fetales que podrían evitarse con un diagnóstico precoz y tratamiento adecuado. Presentamos dos casos clínicos de gestantes con SAF Primario tratadas con heparina de bajo peso molecular y AAS con buen resultado perinatal (AU)