Polyamines (putrescine, spermidine and spermine) are essential for cell growth and differentiation. Nitric oxideexhibits antihypertrophic functions and inhibits cardiac remodelling. However, the metabolism of polyamines and thepotential interactions with nitric oxide in cardiac hypertrophy remain unclear. We randomly divided Wistar rats into fourtreatment groups: controls, isoproterenol (ISO), ISO and -arginine, and -arginine. Isoproterenol (5mg/kg/day, subcutaneously)and/or?-arginine (800 mg/kg/day, intraperitoneally) was administered once daily for 7 days. The expression ofatrial natriuretic peptide mRNA was determined by reverse transcription-polymerase chain reaction, and fibrogenesis ofheart was assessed by Van Gieson staining. Polyamines were measured with high-performance liquid chromatography, andplasma nitric oxide content and lactate dehydrogenase (LDH) activity were determined with a spectrophotometer. Theexpression levels of ornithine decarboxylase, spermidine/spermine N1-acetyltransferase (SSAT), endothelial nitric oxidesynthase (eNOS) and inducible nitric oxide synthase (iNOS) were analysed by Western blot. Heart-to-body weight ratio,left ventricle-to-body weight ratio, atrial natriuretic peptide mRNA expression, collagen fibres and LDH activity wereelevated, both ornithine decarboxylase and SSAT proteins were up-regulated, and total polyamines were increased in thegroup treated with ISO. Additionally, the expression of iNOS was up-regulated, eNOS was down-regulated, and nitricoxide levels were low. Notably, cotreatment with -arginine reversed most of these changes except for SSAT expression,which was further up-regulated. We propose that increased polyamines and decreased nitric oxide are involved in cardiachypertrophy induced by ISO and suggest that -arginine pre-treatment can attenuate cardiac hypertrophy through theregulation of key enzymes of the polyamine and nitric oxide pathways.