Effects of Thyroxine and Propylthiouracil Treatment of Young Male Sprague-Dawley Rats on Potassium-Induced Contraction of Thoracic Aorta
The problem. This study investigated the effects of thyroxine and propylthiouracil treatment of young male Sprague-Dawley rats on aortic ring contraction induced by increasing potassium concentrations. Procedure. Three groups (N=6) of thirty-day-old male Sprague-Dawley rats were treated for nineteen days with thyroxine (200 micrograms by injection), propylthiouracil (via drinking water), or nothing. Starting on the nineteenth day, one rat from each group was sacrificed each day until all rats had Been used. A section of aorta was excised and cleaned of its adventitia, A 2-3 millimeter ring was then cut from the section of aorta. The ring was mounted, placed in a ring bath, stretched to a one gram preload and allowed to incubate. At the end of the incubation period, increasing potassium concentrations were introduced into the indubation chamber in a serial order from low concentration to high concentration. Resulting contractions of the aortic rings due to the increasing potassium concentrations were recorded. Findinqs. The results indicate that treatment with thyroxine and propylthiouracil affected the aortic ring contractility to increasing potassium concentrations. Although statistically significant difference was observed only at the highest concentration of potassium on the percent of maximal response measurement, alterations in contractile strength values were evident. The thyroxine treated group generated consistently lower tensions compared to the euthyroid controls, while the propylthiouracil treated group generated consistently higher tensions than the control group. Conclusion. It can be determined from this study that treatment with thyroxine and propylthiouracil affected generated tension of thoracic aorta rings subjected to increasing potassium concentrations. Although the treatments did not result in significant differences of the contractile strengths, the consistent increases and decreases in generated ring tensions, caused by the treatments with propylthiouracil and thyroxine respectively, suggest that these treatments did affect potassium-induced contractions of the aortic rings.
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