title: Effects of dietary sodium on circadian rhythm and physiological responses of 18-hydroxycorticosterone.
abstract: 1. The effects of dietary sodium intake on plasma 18-hydroxycorticosterone (18-OHB) responses to physiological stimuli and recumbent 24-h-plasma 18-OHB levels have been examined in nine normal male subjects. 2. Basal supine levels of 18-OHB during a 40 mmol of sodium intake period (62.5 +/- 6.0 ng/dl) were considerably greater (P less than 0.0001) than the levels during a 200 mmol of sodium intake period (9.8 +/- 1.2 ng/dl). Further incremental and percentage changes of 18-OHB in response to graded dose infusions of angiotensin II and adrenocorticotropic hormone (ACTH) were greater during the 40 mmol of sodium intake period. 3. Although the mean 24 h levels of plasma 18-OHB during the 40 mmol of sodium intake period (43.9 +/- 4.0 ng/dl) were greater (P less than 0.001) than those during the 200 mmol of sodium intake period (9.4 +/- 1.2 ng/dl), the circadian rhythm of 18-OHB secretion was similar under the two extremes of sodium intake. 4. Factors which increase angiotensin II levels, such as sodium restriction, isometric exercise and angiotensin infusion, selectively increase 18-OHB and aldosterone, suggesting that angiotensin II increases 18-OHB and aldosterone secretion, in part, by modulation of the 18-hydroxylation reaction involved in conversion of corticosterone into 18-OHB.
mesh_terms: D015069:18-Hydroxycorticosterone / Q000097:blood*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology; D000328:Adult; D000450:Aldosterone / Q000097:blood; D000804:Angiotensin II / Q000494:pharmacology; D002940:Circadian Rhythm / Q000187:drug effects; D003345:Corticosterone / Q000031:analogs & derivatives*; D006801:Humans; D008297:Male; D008875:Middle Aged; D005082:Physical Exertion; D011187:Posture; D012964:Sodium / Q000494:pharmacology*
chemical_list: D000804:Angiotensin II; D000450:Aldosterone; D015069:18-Hydroxycorticosterone; D000324:Adrenocorticotropic Hormone; D012964:Sodium; D003345:Corticosterone