Hydralazine treatment alters body composition in the rabbit model of obesity

While hydralazine is commonly used as monotherapy in animal studies, its potential side effects are seldom acknowledged. Purported side effects occur from sympathetic and renin-angiotensin system activation, and include tachycardia, oedema, and nausea. We hypothesized that these side effects would alter body composition by increasing body water and/or decreasing body fat.

Female New Zealand White rabbits were divided into lean and obese control and hydralazine-treated groups. Lean rabbits ate a maintenance diet for 12 weeks; obese rabbits ate an ad lib high fat diet. Hydralazine was administered at 6 and 10-14 mg kg(-1) day(-1) for lean and obese hydralazine groups, respectively. Body composition was determined using triplicate 2-3 g samples of whole body homogenate, and analysed using 2 x 2 ANOVA for diet vs. hydralazine effects.

Hydralazine-treated animals had lower body fat (15.7 +/- 1.1 and 21.8 +/- 1.0%, respectively) and higher body water (59.8 +/- 0.8 and 55.4 +/- 0.6%, respectively) compared with controls. While obese controls were heavier than obese hydralazine-treated animals (5.12 +/- 0.09 vs. 4.73 +/- 0.11 kg, respectively) and had greater overall feed consumption (13.5 +/- 0.4 vs. 11.8 +/- 0.4 kg, respectively), a subsequent analysis using subsets that did not differ in body weight or feed consumption yielded the same conclusions. Plasma adrenaline and noradrenaline did not differ between control and hydralazine-treated groups.

Use of hydralazine to control blood pressure alters body composition. Direct or indirect effects of hydralazine may impact physiological systems under study. Alterations in adipose tissue may be of particular concern because of its endocrine function.