Abstract 245: Role Of Melanocortin-4-receptor In The Blood Pressure Regulation In Female Hyperandrogenemic Rats, A Model Of Polycystic Ovary Syndrome

Abstract

Women with polycystic ovary syndrome (PCOS) are characterized by hyperandrogenemia, hirsutism, infertility, and enlarged cystic ovaries. Obesity and hypertension are also frequently found in women with PCOS, although the mechanisms responsible for the elevated blood pressure (BP) are unclear. Thus we tested the hypothesis that the melanocortin-4 receptor (MC4R), known to contribute to obesity hypertension in males, contributes to the elevated BP in hyperandrogenemic female rats, a model of PCOS. Female Sprague Dawley rats (4 wks) were implanted with dihydrotestosterone (DHT; 7.5mg/90 days sc) or placebo pellets (PL) (n=5/grp) and aged to 12 wks. Body weight and food intake (whether rats were pair fed or had ad libitum access) were measured daily. Two wks following implantation of radiotelemetry transmitters and intracerebroventricular cannulae, baseline mean arterial pressure (MAP) was measured for 5 days; then rats received MC3/4R antagonist, SHU-9119 (SHU; 1 nmol/h ICV) or vehicle for 7 days and MAP was recorded. DHT-treated rats had higher body weight and MAP than PL rats (BW: PL: 266.0±8.7; DHT: 348.5±10.4 g, p<0.01; MAP: PL rats: 102±5; DHT: 114±5 mmHg, p<0.05). SHU significantly increased food intake and body weights in both placebo (PL) and DHT-treated rats fed ad libitum (PL: 379.2±28.5; DHT: 451/3±7.3 g, p<0.01 DHT vs PL; 0.01 SHU vs control), but had no effect on MAP compared to controls (PL: 104±5; HAF rats: 114±5 mmHg; p<0.05, HAF vs PL; p=NS, SHU vs controls). However, in other rats, when pair fed with little increase in body weight (PL: 253.7±2.0, SHU: 261.0±0.6, p<0.05; DHT: 306.7±2.6, SHU: 316.7±1.5 g, p<0.05), SHU decreased MAP in DHT treated rats but not placebo controls (PL rats: 102±1, SHU: 103±2 mmHg; p=NS; DHT rats: 110±1 vs. SHU: 97±1 mmHg; p<0.001). Thus MC4R antagonist reduces MAP in DHT-treated rats only when food intake and body weight are controlled. These data suggest that activation of MC4R contributes to elevated BP in our model of PCOS and may also contribute to the elevated BP in women with PCOS. Supported by NIH R01HL66072, P01HL05971 and AHA 14POST18640015.