Cardiac Histomorphometric Implications Resulting From Chronic Nandrolone Decanoate Treatment in Rats Subjected to Resistance Training

ABSTRACT The effects of anabolic steroid abuse on the cardiac tissue of resistance training practitioners are poorly understood. Herein, we present the histomorphometric implications of resistance training in rats treated with nandrolone decanoate, an androgenic anabolic steroid. Eighteen‐week‐old male Wistar rats ( N = 32) were divided into two groups ( N = 16): vehicle group (VEH; 0.2 mL/kg i.m., peanut oil) and group treated with nandrolone decanoate (NAN; 5 mg/kg i.m.), both for 12 weeks. Half of each group underwent a resistance training protocol (VEH‐T and NAN‐T) during the same period. At the end, the animals were euthanized for cardiac morphometric and histological evaluation. The NAN group presented an increase in left ventricular wall thickness and cardiomyocyte cross‐sectional area, together with a reduction in the percentage area occupied by cardiomyocytes and an increase in interstitial fibrosis percentage, compared with the VEH group. In turn, the VEH‐T group showed increased left ventricular wall thickness, cardiomyocyte cross‐sectional area, and myonuclear number, with no effect on interstitial fibrosis or the percentage area occupied by cardiomyocytes. In contrast, the NAN‐T group exhibited a higher cardiomyocyte cross‐sectional area and myonuclear number than the other groups, together with a lower interstitial fibrosis percentage than the NAN group. Chronic treatment with a supraphysiological dose of nandrolone decanoate resulted in adverse cardiac remodeling and increased interstitial fibrosis. Resistance training promoted cardiac hypertrophy without increasing fibrosis. When combined with nandrolone, training was associated with lower fibrosis values than those observed in untrained nandrolone‐treated animals but did not prevent the major structural alterations associated with nandrolone exposure.