Exercise training may be beneficial in menopausal women by reducing blood pressure, insulin resistance and cholesterol level. The adaptation of the cardiac hormonal systems: oxytocin (OT), natriuretic peptides (NPs) and nitric oxide synthase (NOS) in response to exercise training was investigated in intact and ovariectomized (OVX) rats. Ovariectomy significantly augmented body weight (BW), left ventricle (LV) mass and intra-abdominal fat pad weight and decreased the expression of oxytocin receptor (OTR), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and guanylyl cyclase-A (GC-A), in the right atrium (RA) and LV, indicating estrogenic control of these genes. These effects of ovariectomy were counteracted by 8-week-long exercise training which decreased fat pad weight (33.4 ±2.3 to 23.4 ± 3.1 g, n=8, p<0.05), plasma free fatty acids (0.124 ± 0.033 to 0.057 ± 0.010 mM, n=8, p<0.01), and plasma triacylglycerol (0.978 ± 0.174 to 0.588 ±0.115 mM, n=8, p<0.05). Chronic exercise tended to decrease BW and stimulated ANP (4- to 5-fold) and OTR gene expression in the LV and RA and BNP and inducible NOS (iNOS) mRNA in the LV. In sham-operated rats, exercise augmented ANP expression in the RA, down-regulated GC-A mRNA in the LV and RA, but increased its expression 3-fold in the RA of OVX animals. Endothelial NOS and iNOS expression was enhanced in the left atrium of sham-operated rats. Altogether, these data indicate that in OVX animals, chronic exercise significantly enhances cardiac OT, NPs and NOS, thus implicating all 3 hormonal systems in the beneficial effects of exercise training.