Abstract
Abstract
The possibility that circadian phase of NaCl intake may play a role in the development of hypertension was evaluated with the use of DOCA-implanted rats, receiving either saline (1%) or water as follows: Group I, saline ad libitum; Group II, saline from 6 PM to 6 AM; Group III, saline from 6 AM to 6 PM; Group IV, water ad libitum. All animals were kept on a 12:12 light schedule (lights on from 6 AM to 6 PM) and regular rat chow ad libitum. The mean daily fluid intake (ml/100 g body wt/24 hr) during the first 2 weeks of the experiment was: 57 ± 1.5; 59 ± 1; 45 ± 1; and 25 ± 1.6 for Groups I, II, III, and IV, respectively. On the third experimental week, the mean systolic BP (mm Hg) ± SE was as follows: Group I, 154 ± 4.1; Group II, 140 ± 3; Group III, 154 ± 5; Group IV, 132 ± 4.5. The data suggest that hypertension develops more readily among rats ingesting excessive salt loads while at rest (circadian phase of low natriuresis) than among those doing so during the active phase (circadian phase of high natriuresis) of their day.
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