Anabolic steroids impair the exercise-induced growth of the cardiac capillary bed

Background: Concomitant application of anabolic-androgenic steroids and phy sical exercise can induce cardiac hypertrophy. These experiments investigat e the still unknown response of the cardiac myocytes and capillaries to the combined influence of various anabolic steroids and muscular exercise. Met hods: Female SPF-NMRI mice were divided into the following groups: a) seden tary control, b) exercise (treadmill running); c) sedentary receiving Diana bol: d) exercise + Dianabol: e) exercise + Oral-Turinabol. After 3 and 6 we eks the left ventricular papillary muscles were studied morphometrically, E valuated variables: minimal myocyte diameter, number of capillaries around a single myocyte, capillary density and intercapillary distance. Results: O nly the anabolic steroids c exercise groups showed a mild myocyte hypertrop hy. In contrast, only exercise alone caused a significant increase of the c apillary density after both experimental periods; e.g. capillary density af ter 6 weeks (capillaries/mm(2), mean values + standard deviation, p < 0.05) : control (4272 +/- 287), exercise (5411 +/- 755), dianabol (4004 +/- 333), dianabol + exercise (4076 +/- 403), oral-turinabol + exercise (4053 +/- 30 6). Moreover, unlike all other regimens, only exercise alone shortened the intercapillary distance. Finally, exercise without drugs induced the greate st increase in the number of capillaries around a single myocyte. Conclusio ns: Anabolic steroids combined with exercise: 1) induce mild hypertrophy of the cardiac myocytes, 2) impair the cardiac microvascular adaptation to ph ysical conditioning. The microvascular impairment may cause a detrimental a lteration of the myocardial oxygen supply, especially during muscular exerc ise.