title: Immunoreactive substance P in human plasma: response to changes in posture and sodium balance.
abstract: 1. In healthy volunteers plasma concentrations of immunoreactive substance P were measured in response to changes in posture and dietary salt intake. 2. In 14 subjects plasma immunoreactive substance P was 168 +/- 31 pmol/l when subjects were supine and 401 +/- 51 pmol/l (P less than 0.001) when they were ambulant. 3. Measurement of supine plasma immunoreactive substance P at 6 h intervals gave a mean value of 240 +/- 39 pmol/l at 14.00 hours and a lowest value of 76 +/- 9 pmol/l at 02.00 hours. 4. In eight healthy subjects plasma immunoreactive substance P rose only slightly from 169 +/0 41 pmol/l, on a sodium intake ad lib., to 244 +/- 45 pmol/l by day 4 of dietary sodium restriction (35 mmol/day) and significantly fell to 51 +/- 20 pmol/l (P less than 0.001) by day 4 of high sodium intake (350 mmol/day). 5. Although exogenous substance P was shown to be natriuretic in dog and rat, the present results do not favour a role of endogenous substance P as a circulating natriuretic factor in man.
mesh_terms: D000328:Adult; D002940:Circadian Rhythm; D004039:Diet, Sodium-Restricted; D005260:Female; D006801:Humans; D008297:Male; D011187:Posture; D012965:Sodium Chloride / Q000008:administration & dosage*; D013373:Substance P / Q000097:blood*
chemical_list: D013373:Substance P; D012965:Sodium Chloride