Role of the Adrenal Medullae in Male and Female DOCA-Salt Hypertensive Rats

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Abstract
Female rats treated with deoxycorticosterone acetate (DOCA) and salt do not get as hypertensive as male DOCA-salt treated rats. The adrenal gland contributes to the development and maintenance of DOCA-salt hypertension in male rats. However, little is known about adrenal medullary function in DOCA-salt hypertensive female rats. This study tested the hypothesis that bilateral removal of the adrenal medullae would result in a greater fall in blood pressure in male DOCA-salt compared to female DOCA-salt rats. Five weeks after initiating DOCA-salt treatment, average 24 hour mean arterial pressure (MAP) in female rats was significantly attenuated compared to male rats (142±4 versus 168±6 mm Hg, respectively). Female DOCA-salt rats consumed significantly more saline per day than male DOCA-salt rats (22.3±1.8 versus 33.4±1.8 mL/100 grams 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 observed in female DOCA-salt rats (150±6 to 135±3 mm Hg). In the following 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. Adrenal medullectomy significantly increased heart rate (HR) in all groups for 12 days. Male sham and DOCA-salt rats had significantly higher catecholamine content in the adrenal medulla than female sham and DOCA-salt rats, respectively. These data suggest that the adrenal medullae contribute more to the maintenance of blood pressure in DOCA-salt hypertension in male rats than female rats.