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Dose-dependency of clonidine's effects in ascitic cirrhotic rats: comparison with α1-adrenergic agonist midodrine
Giovanni Sansoè1, Manuela Aragno2, Raffaella Mastrocola2
1Division of Gastroenterology, Gradenigo Hospital, Torino, Italy.
Background & Aims:
Sympathetic nervous system (SNS) activation decreases response to diuretics, but both α1-adrenoceptor agonists and sympatholytic α2-adrenoceptor agonists are recommended in the management of ascitic cirrhosis. We intend to compare the effects of increasing doses of clonidine (α2-agonist) vs. midodrine (α1-agonist) in advanced cirrhosis.
Methods:
Renal function, mean arterial pressure (MAP), and hormonal status were measured in rats with ascitic cirrhosis due to 13-week CCl(4) administration (groups G1-G5), in control rats (Gc), and in rats with ascitic cirrhosis untreated (G6) or treated with daily diuretics (0.5 mg/kg furosemide plus 2 mg/kg K(+) -canrenoate during the 11(th) -13(th) weeks of CCl(4)) (G7). G1-G5 cirrhotic rats received daily, during the 11(th)-13(th) CCl(4) weeks: clonidine 0.3 μg only (G1), diuretics + clonidine 0.2 (G2), 0.5 (G3) or 1 μg (G4), and diuretics + midodrine 1 mg/kg b.w. (G5).
Results:
Cirrhotic rats in G1 or G2 had higher glomerular filtration rate, renal plasma flow and natriuresis than cirrhotic rats treated with diuretics (G7) (all P < 0.05). The addition of clonidine 0.2 μg to diuretics (G2 vs. G7) reduced serum norepinephrine (169 ± 71 ng/L vs. 523 ± 88 ng/L) and plasma renin activity (12 ± 3 ng/ml/h vs. 25 ± 5 ng/ml/h) (all P < 0.05). Midodrine did not improve the renal performance in ascitic rats treated with diuretics. In comparison to absolute cirrhotic controls (G6), MAP was lower in G4 and higher in G5 (all P < 0.05).
Conclusion:
Low-dose α2-agonists improve natriuresis and reduce SNS function and hyper-aldosteronism without affecting arterial pressure in experimental ascitic cirrhosis treated with diuretics.
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