Cardiovascular and survival effects of sympatho-inhibitors in adriamycin-induced cardiomyopathy in rats.

Adriamycin (ADR) is a widely used drug for the treatments of cancers. This study evaluates the effects of moxonidine and metoprolol on cardiac hemodynamics and survival in ADR-induced left ventricular dysfunction (total dose of 20 mg/kg in a 4-week regimen). Rats were treated with the centrally acting I(1)R agonist sympatho-inhibitor, moxonidine, or with the non-selective beta-adrenergic antagonist, metoprolol, during 1 month or until death. Treatments began 1 week after the onset of the ADR administration. Low doses (0.5 and 1 mg/kg/day) of moxonidine and metoprolol (10 mg/kg/day) improved cardiovascular function. High doses of moxonidine (3 mg/kg/day) and metoprolol (150 mg/kg/day) were cardiodepressive. Moxonidine and metoprolol both failed to improve survival. These data indicate that a treatment with these sympatho-inhibitors can reduce the left ventricular dysfunction induced by ADR. Moreover, these cardioprotective effects where obtained even when ADR was used at a dose regimen usually employed for its antineoplastic effects in rodents. Nevertheless, in this particular cardiomyopathy, we did not find any association between improvements of functional parameters and survival whatever the drug and the dose used. This problem points out the difficulty to prevent, at least with sympatho-inhibitory drugs alone, the mortality linked to the chronic cardiotoxicity of ADR.

Effect of i1 imidazoline receptor agonist, moxonidine, in nitric oxide-deficient hypertension in pregnant rats.

Decreased nitric oxide production has been reported in preeclampsia, which is also frequently associated with glucose intolerance. It was thus considered of interest to investigate the effects of moxonidine, a centrally acting antihypertensive drug that reduces insulin resistance, in a rat model of preeclampsia. Hypertension was induced in Wistar rats by dietary l-NNA (N(omega)-nitro-L-arginine, 0.063%, 31 mg/kg/d, days 13-19 of gestation) and, over the same period, moxonidine or vehicle was administered orally (2 mg/kg/d by gavage). On day 20, blood pressure was measured in the pentobarbital anesthetized animals, glucose tolerance was tested (2 g/kg glucose i.p.), and morphologic studies were conducted on the litter to determine the benefits with respect to fetal outcome. Hypertension was reduced with daily moxonidine treatment (P < 0.05). Basal plasma insulin and insulin/glucose index were decreased with moxonidine treatment evidencing improved insulin sensitivity in the control and l-NNA-treated pregnant rats (P < 0.05). After glucose challenge, plasma insulin increased in all the groups as expected and plasma insulin and insulin/glucose index were significantly higher in the l-NNA group than in the control, moxonidine, or l-NNA + moxonidine groups (P < 0.05 for time 60 minutes). Thus, moxonidine improved glucose tolerance in l-NNA-treated pregnant rats. Moreover, moxonidine treatment very effectively decreased the number of necroses (1 necrosis in 71 fetuses in the l-NNA + moxonidine group versus 15 necroses in 79 fetuses in the l-NNA group, P < 0.01). In conclusion, the 7-day treatment with moxonidine suppressed hypertension and reduced glucose intolerance and fetal necrosis, thus demonstrating the effectiveness of moxonidine in the preeclamptic model.