The effects of endurance training and anabolic steroid (Methandienone 1.5 mg.kg-1 p. o. daily) and their combination on regional collagen biosynthesis and concentration in the hearts of male beagle dogs were studied by measuring prolyl 4-hydroxylase (PH) activity and hydroxyproline (HYP) concentration. The PH (P less than 0.05) and HYP (P less than 0.05) were both greater in the subendocardinal layer than in the subepicardium (EPI) of the left ventricular wall in controls, whereas opposite gradients (P less than 0.05) were observed in the right ventricle. Endurance exercise caused an increase of PH activity in EPI of the left ventricular wall (P less than 0.01). The HYP concentration increased in both layers of the right ventricle in the exercise plus steroid group (P less than 0.05). The results suggest that transmural differences exist in the rate of collagen synthesis and concentration in canine cardiac ventricles and that endurance exercise may accelerate collagen synthesis in EPI of the left ventricle and the combination of exercise and anabolic steroid causes an increase in collagen concentration in the right ventricular wall.

The effects of endurance training, anabolic steroid (methandione 1.5 mg/kg p.o. daily) and their combination on the activities or aryl sulphatase, B-glucuronidase and cathepsin D, all lysosomal hydrolytic enzymes, were studied in the heart of male beagle dogs. Training caused significant increase in the B-glucuronidase activity in the right ventricular wall. Anabolic steroid as such caused no change in any enzymic activities, whereas exercise combined with steroid treatment resulted in significant increases in the activities of all enzymes studied in the right ventricular wall. The combined effect of exercise training and anabolic steroid on the lysosomal hydrolytic enzymes may reflect and mediate the previous observed degenerative effects of this combination in the heart.

The changes of mean outflow resistance (MOR) (defined as the ratio between mean aortic ejection pressure and mean ejection rate) and of total peripheral resistance (TPR) together with their relations to some circulatory parameters and to each other were studied under control (NaCl) and six different loading conditions on anesthetized closed chest dogs. Phenylephrine increased both MOR and TPR (ca. 160%, max), pacing increased MOR (p less than 0.01) but not TPR. Isoproterenol and dextran infusion decreased TPR (p less than 0.001) but not MOR. Calcium chloride decreased MOR (p less than 0.05) but increased TPR (NS). The relationship between MOR and TPR was linear in each case (r from 0.63 to 0.91). Both MOR and TPR showed either positive or negative linear correlations with volume and pressure parameters although MOR appeared to be more sensitive to the administered interventions. The present results suggest that, when referring to the pulsatile and discrete nature of the blood-flow-pressure output from the left ventricle, MOR seems to be a more useful measure than TPR in the assessment of the left ventricular afterload.

The effect of an anabolic steroid on canine left ventricular function was studied by catheterization exposing control (n = 7) and methandienone-treated (n = 6) dogs to pacing, volume and isoproterenol tests at the beginning of the experiment and 6 weeks later. The physical performance of the animals was evaluated by submaximal exercise test (SMT), in which the steroid-treated dogs had lower heart rate than the sedentary controls (P less than 0.001). Heart weight was greater in the steroid than in the control group (P less than 0.05). Isoproterenol infusion increased the maximum value of the left ventricular pressure curve (dP/dtmax) less in the steroid-treated than in the control animals (P less than 0.05). Also heart rate was lower in the steroid than in the control group after inotropic load, while end-diastolic, end-systolic and stroke volumes decreased significantly more in the control group (P less than 0.05). Systemic vascular resistance decreased in the steroid treated animals, but remained unchanged in the control group (P less than 0.05 between the groups). During volume overload dP/dtmax increased in the control group but decreased slightly in the steroid group (P less than 0.05 between the groups). The pressure-volume diagram showed that the left ventricle of the steroid-treated animals worked on higher ventricular volumes than in the control group. In conclusion, long-term methandienone treatment results in cardiac hypertrophy in dogs, reduces its response to an inotropic loads and leads to working on larger ventricular volumes.

To investigate the effects of endurance training on myocardial performance seven beagle dogs (exercise group, EG) were trained by treadmill running for 6-7 wk. Before and after experimental period the EG and control group (CG, n = 7) underwent a standard submaximal exercise test (SMT), and hemodynamic status was checked during anesthesia by catheterization technique exposing the animals to different loadings: pacing, volume loading, and isoproterenol infusion. The increase of heart rate during SMT was about 30 beats/min less in the EG than in the CG. A highly linear relationship between stroke work and end-diastolic volume was observed within the groups (for EG r = 0.953, for CG r = 0.846), but the slope of the regression line obtained for EG appeared to be significantly (P less than 0.001) greater. In EG isoproterenol induced increases in end-diastolic (27%), end-systolic (37%), and stroke volumes (19%), but, on the contrary, decreases of these volumes in CG (19, 15, and 22%, respectively); ejection fraction remained unchanged for both EG and CG. Ventricular stroke work was significantly greater in EG. Systemic vascular resistance decreased in EG in every loading test. The results indicate an improved pump performance, which is related not only to the heterometric autoregulatory adjustments, but also to extracardial adaptations.