In this study, we tested whether estrogen deficiency is associated with oxidative stress and decreased nitric oxide (NO) production, which could be responsible for an increased blood pressure in ovariectomized rats. Hemodynamic studies were performed on conscious, chronically instrumented rats. Chronic estrogen replacement on ovariectomized rats lowered blood pressure approximately 13 mmHg, from 119 +/- 3 mmHg in ovariectomized rats to 106 +/- 3 mmHg in ovariectomized-treated rats; it was also accompanied by an increase in cardiac index and vascular conductance, achieving hemodynamic values similar to those shown by sham-operated rats. N(G)-nitro-L-arginine methyl ester administration lowered significantly less the vascular conductance (0.14 +/- 0.01 vs. 0.22 +/- 0.03 and 0.26 +/- 0.01 ml. min(-1). mmHg(-1)/100 g; P < 0.05) in ovariectomized rats than in the sham-operated and estrogen-treated ovariectomized rats, respectively. Estrogen replacement prevented the lower plasma levels of nitrites/nitrates observed in ovariectomized rats. The lower plasma total antioxidant status and reduced thiol groups and the increase in plasma lipoperoxides presented in ovariectomized animals were reestablished with the estrogen treatment. These results show that estrogen administration decreases blood pressure and increases vascular conductance in ovariectomized rats. This effect may be related to an increase in NO synthesis and/or preventing oxidative stress, then improving endothelial function.

This study investigated the effect of salt intake and angiotensin II (ANG II) levels on microvessel density (MVD). Rats with indwelling arterial and venous catheters were placed on either a high-salt (HS; 4%) or a low-salt diet (LS; 0.4%) for 2 or 4 wk, and blood pressure, heart rate, and plasma renin activity were measured. Plasma ANG II was fixed at normal levels in half of the rats on HS by continuous intravenous infusion of ANG II (5 ng.kg-1.min-1). Samples of cremaster muscle were examined histologically to determine MVD. No difference in MVD was observed between HS and LS groups after 2 wk. After 4 wk on HS, MVD was reduced (22.4%, P less than 0.05) compared with the LS group. In rats fed HS, ANG II infusion induced a significant dose-dependent increase in MVD from 85.11 +/- 3.34 to 98.94 +/- 4.62 (ANG II, 5 ng.kg-1.min-1) and to 107.60 +/- 7.00 (ANG II, 10 ng.kg-1.min-1) (P less than 0.05), with no change in blood pressure. Maintenance of ANG II levels for 4 wk blocked the rarefaction due to salt. These results suggest that the decrease in MVD due to salt could be the result of a dietary-induced fall in plasma ANG II levels.

The present study evaluated the effects of heme oxygenase-1 (HO-1) induction on the changes in renal outer medullary nitric oxide (NO) and peroxynitrite levels during 45-min renal ischemia and 30-min reperfusion in anesthetized rats. Glomerular filtration rate (GFR), outer medullary blood flow (OMBF), HO and nitric oxide synthase (NOS) isoform expression, and renal low-molecular-weight thiols (-SH) were also determined. During ischemia significant increases in NO levels and peroxynitrite signal were observed (from 832.1 +/- 129.3 to 2,928.6 +/- 502.0 nM and from 3.8 +/- 0.7 to 9.0 +/- 1.6 nA before and during ischemia, respectively) that dropped to preischemic levels during reperfusion. OMBF and -SH significantly decreased after 30 min of reperfusion. Twenty-four hours later, an acute renal failure was observed (GFR 923.0 +/- 66.0 and 253.6 +/- 55.3 microl.min(-1).g kidney wt(-1) in sham-operated and ischemic kidneys, respectively; P < 0.05). The induction of HO-1 (CoCl(2) 60 mg/kg sc, 24 h before ischemia) decreased basal NO concentration (99.7 +/- 41.0 nM), although endothelial and neuronal NOS expression were slightly increased. CoCl(2) administration also blunted the ischemic increase in NO and peroxynitrite (maximum values of 1,315.6 +/- 445.6 nM and 6.3 +/- 0.5 nA, respectively; P < 0.05), preserving postischemic OMBF and GFR (686.4 +/- 45.2 microl.min(-1).g kidney wt(-1)). These beneficial effects of CoCl(2) on ischemic acute renal failure seem to be due to HO-1 induction, because they were abolished by stannous mesoporphyrin, a HO inhibitor. In conclusion, HO-1 induction has a protective effect on ischemic renal failure that seems to be partially mediated by decreasing the excessive production of NO with the subsequent reduction in peroxynitrite formation observed during ischemia.

These results show that depletion of the liver glutathione increases the oxidative stress and decreases nitric oxide synthesis of LPS-induced shock in rats.

No abstract

In conscious rats with experimental cirrhosis without ascites, we have studied whether there is a limited cardiac preload reserve by performing cardiac output (CO) curves. CO was determined by thermodilution at basal, 5, 7.5, and 10 cmH2O of right atrial pressure (RAP). RAP was elevated by dextran infusion (1 ml/min iv, 30 min). CO curves were performed by plotting changes in CO with changes in RAP. In the basal state, cirrhotic rats showed a hyperdynamic circulation defined by increased CO and stroke volume, decreased total peripheral resistances, and normotension without changes in heart rate. Blood volume was also elevated in cirrhotic rats compared with the control animals. Between the limits of RAP studied, the CO curve of control rats presented a typical ascending limb. In contrast, the CO curve of the cirrhotic animals showed first an ascending shifted upward limb and afterward a descending limb. These alterations were accompanied by changes in the inotropic state as measured as left ventricular (LV) peak dP/dt in hexamethonium-pretreated animals submitted to the same volume loads described above. With the same increases in RAP, LV dP/dt changed, in every group, in a manner similar to CO. The results of the present study indicate that cirrhotic rats with high blood volume and hyperdynamic circulation show, in the steady state, a limited preload reserve. The partial utilization of the preload reserve can make the cirrhotic heart unable to modulate cardiac performance with changes in loading conditions, thus determining a state of heart failure.

Females suffer a less severe ischemic acute renal failure than males, apparently because of higher nitric oxide (NO) bioavailability and/or lower levels of oxidative stress. Because the renal ischemic injury is associated with outer medullary (OM) endothelial dysfunction, the present study evaluated sex differences in OM changes of NO and peroxynitrite levels (by differential pulse voltammetry and amperometry, respectively) during 45 min of ischemia and 60 min of reperfusion in anesthetized Sprague-Dawley rats. Endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) protein expression and their phosphorylated forms [peNOS(Ser1177) and pnNOS(Ser1417)], 3-nitrotyrosine, reduced sulfhydryl groups (-SH), and glomerular filtration rate (GFR) were also determined. No sex differences were observed in monomeric eNOS and nNOS expression, NO, or 3-nitrotyrosine levels in nonischemic kidneys, but renal -SH content was higher in females. Ischemia increased dimeric/monomeric eNOS and nNOS ratio more in females, but the dimeric phosphorylated peNOS(Ser1177) and pnNOS(Ser1417) forms rose similarly in both sexes, indicating no sex differences in nitric oxide synthase activation. However, NO levels increased more in females than in males (6,406.0 ± 742.5 and 4,058.2 ± 272.35 nmol/l respectively, P < 0.05), together with a lower increase in peroxynitrite current (5.5 ± 0.7 vs. 12.7 ± 1.5 nA, P < 0.05) and 3-nitrotyrosine concentration, (28.7 ± 3.7 vs. 48.7 ± 3.7 nmol/mg protein, P < 0.05) in females than in males and a better preserved GFR after ischemia in females than in males (689.7 ± 135.0 and 221.4 ± 52.5 μl·min(-1)·g kidney wt(-1), P < 0.01). Pretreatment with the antioxidants N-acetyl-L-cysteine or ebselen abolished sex differences in peroxynitrite, nitrotyrosine, and GFR, suggesting that a greater oxidative and nitrosative stress worsens renal damage in males.

No abstract