The effects of 17 alpha-methyltestosterone on myocardial function in vitro.

Testosterone analogs have been used as performance enhancers by athletes for more than 40 yr. We asked whether the anabolic steroid 17 alpha-methyl-4-androstene-17-ol-3-one (17 alpha-MT) would affect intrinsic contractile function of the heart. Male Sprague-Dawley rats, 125-150 g, were treated with 17 alpha-MT either parenterally or orally for up to 8 wk. Intrinsic contractile function of the hearts was assessed utilizing both the isolated working heart and isovolumic perfused heart preparations. Isolated working hearts from 17 alpha-MT-treated rats had a 45% decrease in heart work attributable largely to a similarly decreased stroke volume. Isovolumic perfused hearts from treated animals had elevated left ventricular systolic and diastolic pressures at similar interventricular volumes compared to controls. Rates of ventricular pressure development (+dP/dT) or relaxation (-dP/dT) were unchanged as a result of the treatment. However, static elastance was reduced in potassium-arrested hearts from the 17 alpha-MT treatment (63% increase in interventricular pressure), consistent with a limitation being imposed on stroke volume by a decreased myocardial compliance. Hydroxyproline content of the hearts was not altered by 17 alpha-MT treatment suggesting that increased stiffness was not a consequence of collagen proliferation. Treatment of the steroid rats with beta-aminopropionitrile, a compound that inhibits lysyl oxidase, restored the left ventricular volume-pressure relationship (elastance curve) to that of control hearts. Thus, chronic treatment with anabolic steroids appears to reduce left ventricular compliance, possibly related to an enhanced activity of lysyl oxidase, and results in increased crosslink formation between collagen strands in the extracellular matrix.

The effect of clenbuterol and recombinant erythropoietin on tumor growth and the anemia caused by the Walker 256 carcinosarcoma.

In patients with advanced cancer, anemia is a common complication indicative of a poor prognosis. Attempts to alleviate this have met with mixed success and interventions including erythropoietin often fail to elicit an appropriate response. We have used rats implanted with the Walker 256 carcinosarcoma as a model of non-responsive anemia. This study demonstrates that the provision of recombinant erythropoietin in the presence of clenbuterol, a beta2 agonist, attenuates both the cancer induced anemia and the growth of the tumor in this model. We hypothesize that this treatment relieves the tumor induced inhibition of hematopoiesis, which allows for not only an increase in hematocrit but an increased immunosurveillance resulting in tumor suppression.

The effect of dichloroacetate on the isolated no flow arrested rat heart.

Ischemic dysfunction, including contracture, has been attributed to lack of ATP, although previous work has not been consistent with this concept. We describe here a model of no flow ischemic arrest, characterized by depressed levels of mechanical function upon reperfusion and high energy phosphate stores within normal limits. The decreased mechanical function bears an inverse relationship to myocardial lactate levels after twenty-minutes of reperfusion in the absence or presence of dichloroacetic acid (DCA). Post-ischemic non-DCA treated hearts attained peak work of only 25% of that of controls, while those treated with DCA following ischemia performed almost as well as controls. ATP and CP levels remained high in both DCA treated and non-DCA treated hearts. Lactate levels were high in hearts immediately following ischemia, but were reduced to control levels in post-ischemic hearts perfused with DCA within twenty minutes, whereas those not treated with DCA had lactate levels two to three times that of controls within the same time period. Pyruvate dehydrogenase (PDH) activity was reduced in non-DCA treated post ischemic hearts after twenty minutes reperfusion but was elevated above controls in hearts reperfused with DCA. The data indicates that DCA increases mechanical performance of the isolated post-ischemic rat heart and the proposed mechanism for this increase is the oxidative removal of lactate resulting from an increase in PDH activity.