Gonadectomy and hormonal replacement changes systolic blood pressure and ventricular myosin isoenzyme pattern of spontaneously hypertensive rats.

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Abstract
We investigated the influence of testosterone on systolic blood pressure, heart weight, body weight, and ventricular myosin isoenzyme pattern of male spontaneously hypertensive stroke-prone rats (SHRSP). In two different study series (study 1, postpubertal; study 2, prepubertal), SHRSP were gonadectomized (HG), gonadectomized and replaced with dihydrotestosterone (HG-T), and sham-operated (H). Blood pressure was significantly higher in HG-T animals in both study series. Only prepubertal gonadectomy (study 2, HG group) led to a significantly decreased blood pressure. Heart weight and body weight were significantly diminished in the HG group when compared to the H group in study 2. Dihydrotestosterone (HG-T group) reversed this effect. In both study series gonadectomy shifted the myosin isoenzyme pattern to the V3 form while testosterone replacement led to a myosin isoenzyme pattern in favor of the V1 form. We conclude that the ventricular myosin isoenzyme pattern is under the dominant control of androgens and dissociates the expression of myosin isoenzyme from both blood pressure and cardiac hypertrophy in spontaneously hypertensive rats.