Abstract P038: Testosterone Supplements Have Differential Effects on Blood Pressure in Old and Young Male Spontaneously Hypertensive Rats

Testosterone (“T”) supplements are widely used by men to improve their quality of life, libido, and protect against osteoporosis. In clinical studies, both high and low “T” levels were found to be associated with hypertension and cardiovascular risk. Endogenous “T” levels are reduced in obese men and rats. We have shown previously that “T” supplements in middle-aged (6 mos) obese Zucker rats improved symptoms of the metabolic syndrome and caused weight loss, but increased their blood pressure. How “T” supplements affect hypertensive men and rats is unknown. We hypothesized that “T” supplements would further increase blood pressure (BP) in both old and young male spontaneously hypertensive rats (SHR). Old (O=20-22 mos) and young (Y=10 wks) male SHR were treated with “T” (testosterone propionate 8 mg/10 mm silastic pellet; OT and YT, implanted sc) or placebo (empty pellets; OP and YP, sc). Pellets were changed every 3 weeks for 8 weeks. Mean arterial pressure (MAP) was measured by telemetry for 2 weeks. MAP in OP was higher than in YP (OP: 166±7 vs YP: 148±0.5 mmHg, p<0.001). As we predicted, “T” increased MAP in YT (YP: 148±1 vs YT: 157±1 mmHg, p<0.001). In contrast, “T” decreased MAP in OT (OP: 166±1 vs OT: 155±1 mmHg, p<0.001). These data suggest that in younger men, especially men who are already hypertensive, blood pressure should be monitored closely during “T” supplementation in order to prevent further cardiovascular disease. Since “T” reduced MAP in older male SHR, these data suggest that “T” supplements may not be as detrimental in older hypertensive men as in young men. Future studies will need to be done to determine the mechanisms by which “T” increases BP in young males and the mechanisms by which “T” reduces BP in old males. Supported by NIH-R01HL66072, PO1HL51971 (JFR), 14POST18640015 (ROM), EFF Endocrine Res Grant (LLY).