ROLE OF THE ADRENAL MEDULLAE IN MALE AND FEMALE DOCA-SALT HYPERTENSIVE RATS

Female rats treated with deoxycorticosterone acetate (DOCA) and salt d o not get as hypertensive as male DOCA-salt treated rats. The adrenal gland contributes to the development and maintenance of DOCA-salt hype rtension in male rats. However, little is known about adrenal medullar y function in DOCA-salt hypertensive female rats. This study tested th e hypothesis that bilateral removal of the adrenal medullae would resu lt in a greater fall in blood pressure in male DOCA-salt compared to f emale DOCA-salt rats. Five weeks after initiating DOCA-salt treatment, average 24 hour mean arterial pressure (MAP) in female rats was signi ficantly attenuated compared to male rats (142+/-4 versus 168+/-6 mm H g, respectively). Female DOCA-salt rats consumed significantly more sa line per day than male DOCA-salt rats (22.3+/-1.8 versus 33.4+/-1.8 mL /100 prams body weight, respectively), Following adrenal medullectomy, DOCA-salt males experienced a significant decrease in MAP during the dark period after surgery (182+/-4 to 154+/-4 mm Hg) that was not obse rved in female DOCA-salt rats (150+/-6 to 135+/-3 mm Hg). In the follo wing light period, MAP remained significantly decreased when compared to the light period before surgery in DOCA-salt male (171+/-4 to 156+/ -4 mm Hg), while no effect was observed in DOCA-salt female rats. Adre nal medullectomy significantly increased heart rate (HR) in all groups for 12 days. Male sham and DOCA-salt rats had significantly higher ca techolamine content in the adrenal medulla than female sham and DOCA-s alt rats, respectively. These data suggest that the adrenal medullae c ontribute more to the maintenance of blood pressure in DOCA-salt hyper tension in male rats than female rats.