Abstract-Cardiac hypertrophy is often associated with an increased sympathetic drive, and both in vitro and in vivo studies have demonstrated the development of cardiomyocyte hypertrophy in response to either ␣-or ␤-adrenergic stimulation. Because an association between the Na ϩ /H ϩ exchanger and cellular growth has been proposed, this study aimed to analyze the possible role of the antiporter in isoproterenol-induced cardiac hypertrophy. Isoproterenol alone (5 mg/kg IP once daily) or combined with a selective inhibitor of the Na ϩ /H ϩ exchanger activity (3 mg · kg) was given to male Wistar rats for 30 days. Sex-and age-matched rats that received 0.9% saline IP daily served as controls. Echocardiographic follow-up showed a 33% increase in left ventricular mass in the isoproterenol-treated group, whereas it did not increase in the isoproterenolϩBIIB723-treated group. Heart weight-to-body weight ratio at necropsy was 2.44Ϯ0.11 in controls and increased to 3.35Ϯ0.10 (PϽ0.05) with isoproterenol, an effect that was markedly attenuated by BIIB723 (2.82Ϯ0.07). Intense cardiomyocyte enlargement and severe subendocardial fibrosis were found in isoproterenol-treated rats, and both effects were attenuated by BIIB723. Myocardial Na ϩ /H ϩ exchanger activity and protein expression significantly increased in isoproterenol-treated rats compared with the control group (1.45Ϯ0.11 vs 0.91Ϯ0.05 arbitrary units, PϽ0.05). This effect was significantly reduced by BIIB723 (1.17Ϯ0.02, PϽ0.05). In conclusion, our results show that Na ϩ /H ϩ exchanger inhibition prevented the development of isoproterenolinduced hypertrophy and fibrosis, providing strong evidence in favor of a key role played by the antiporter in this model of cardiac hypertrophy. Key Words: hypertrophy, cardiac Ⅲ signal transduction Ⅲ antiporters Ⅲ fibrosis Ⅲ adrenergic receptor agonists I ncreased sympathetic activity is often implicated in the development of cardiac hypertrophy (CH). A correlation between cardiac mass and sympathetic activity was found in young hypertensive humans, 1 and long-term infusion of subpressor doses of norepinephrine leads to CH in dogs and rats. 2,3 This cardiotrophic effect of catecholamines involves both ␣-or ␤-adrenergic receptors. 4 It is well recognized that repeated or continuous injections of the ␤-adrenoceptor agonist isoproterenol (Iso) causes, within days, clear CH, 5 and therefore it represents a useful experimental model.Although several mechanisms have been imputed to underlie the cardiotrophic action of Iso, 5-7 the exact nature is still under debate. Because cumulative evidence supports a cause-effect link between the activity of the Na ϩ /H ϩ exchanger (NHE) and cardiac cell growth (Cingolani and Camilión de Hurtado 8 ), we sought to analyze the possible role of NHE activity in Iso-induced CH by taking advantage of the specific, orally active inhibitor against NHE isoform 1 (NHE-1). This study provides evidence indicating a key role for NHE-1 activity as a mechanism underlying the development of CH and fibrosis induced by I...

Objective: To explore the effects of transient correction of enhanced corticoadrenal activity in monosodium L-glutamate (MSG)-damaged female rats on peripheral insulin sensitivity and in vitro retroperitoneal (RP) adipocyte function. Designs: A dose of 4 mg/g body weight (BW) of MSG or vehicle (CTR) was i.p. injected, once every 2 days, between days 2 and 10 of age, in female rats. Intact and 21 day-operated (sham or adrenal enucleation (AE)) rats from both (CTR and MSG) groups were used for experimentation on day 120 of age. Circulating levels of several hormones, in basal and after i.v. high-glucose load conditions, and RP adiposity morphology and function were then evaluated. Results: MSG rats developed increased adrenocortical function, hyperadiposity, hyperleptinemia, hyperinsulinemia and decreased peripheral insulin sensitivity. These characteristics were fully reversed after transient correction of corticoadrenal hyperactivity induced by AE. In addition, in vitro experimentation with isolated RP adipocytes indicated that cells from intact MSG animals displayed decreased sensitivity to insulin and dexamethasone stimulation of leptin secretion. Interestingly, adipocyte dysfunction in MSG rats was fully abrogated after AE-induced transient correction of insulinemia, leptinemia and adrenocortical activity. Importantly, the reversion of these metabolic abnormalities, induced by AE for 21 days, in MSG animals did occur, despite no significant changes in BW values. Conclusion: Our results support that the changes in adipocyte characteristics and peripheral insulin resistance, developed in this pseudo-obese female rat model, are mainly due to increased glucocorticoid production. Importantly, appropriate correction of the enhanced adrenocortical activity fully reversed these abnormal functions.

In rats, learning and memory performance decline during aging, which makes this rodent species a suitable model to evaluate therapeutic strategies of potential value for correcting age-related cognitive deficits. Some of these strategies involve neurotrophic factors like insulin-like growth factor-I (IGF-I), a powerful neuroprotective molecule in the brain. Here, we implemented 18-day long intracerebroventricular (ICV) IGF-I gene therapy in 28 months old Sprague-Dawley female rats, and assessed spatial memory performance in the Barnes maze. We also studied hippocampal morphology using an unbiased stereological approach. Adenovectors expressing the gene for rat IGF-I or the reporter DsRed were used. Cerebrospinal fluid (CSF) samples were taken and IGF-I levels determined by radioimmunoassay. At the end of the study, IGF-I levels in the CSF were significantly higher in the experimental group than in the DsRed controls. After treatment, the IGF-I group showed a significant improvement in spatial memory accuracy as compared with DsRed counterparts. In the dentate gyrus (DG) of the hippocampus, the IGF-I group showed a higher number of immature neurons than the DsRed controls. The treatment increased hippocampal astrocyte branching and reduced their number in the hippocampal stratum radiatum. We conclude that the ependymal route is an effective approach to increase CSF levels of IGF-I and that this strategy improves the accuracy of spatial memory in aging rats. The favorable effect of the treatment on DG neurogenesis and astrocyte branching in the stratum radiatum may contribute to improving memory performance in aging rats.

The aim of this work was to assess the possible correlation between oxidative damage and the development of cardiac hypertrophy in heart tissue from young (40-d-old) and older (4-, 11-and 19-month-old) spontaneously hypertensive rats (SHR) in comparison with age-matched Wistar (W) rats. To this end, levels of thiobarbituric acid reactive substances (TBARS), nitrotyrosine contents, NAD(P)H oxidase activity, superoxide production, and the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were determined. Compared to age-matched normotensive rats, SHR showed a significant increase in systolic blood pressure from 40 d of age and left ventricular hypertrophy (LVH) was significantly evident from 4 months of age. W rats (11-and 19-month-old) also showed an increase in LVH with aging. TBARS and nitrotyrosine levels were similar in young rats from both strains and were significantly increased with age in both strains, with the values in SHR being significantly higher than those in age-matched W rats. NAD(P)H activity was similar in young SHR and W rats, whereas it was higher in aged SHR compared with age-matched W rats. Compared to W rats, superoxide production was higher in aged SHR, and was abolished by NAD(P)H inhibition with apocynin. CAT activity was increased in the hearts of 4-month-old SHR compared to age-matched W rats and was decreased in the hearts of the oldest SHR compared to the oldest W rats. SOD and GPx activities decreased in both rat strains with aging. Moreover, an increase in collagen deposition with aging was evident in both rat strains. Taken together, these data showed that aged SHR exhibited higher cardiac hypertrophy and oxidative damage compared to W rats, indicating that the two undesirable effects are associated. That is, oxidative stress appears to be a cause and/or consequence of hypertrophy development in this animal model. (Hypertens Res 2008; 31: 1465-1476)

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