Effect of Rehydration Fluid Osmolality on Plasma Volume and Vasopressin in Resting Dehydrated Men

摘要

Elevated plasma vasopressin concentration (PVP), which may act as a dipsogen, decreases promptly following the ingestion of fluids in many mammals including humans. The purpose for this study was to determine whether fluids of varied electrolyte and carbohydrate composition and osmolality (Osm) would modify post-drinking decreases in (PVP) which could be attributed to interaction with plasma volume (PV)- or fluid-electrolyte interactive hormones. Five men (23-41 yr, 78.0 +/- SD 8.2 kg), water deprived for 24 h, drank six fluids (12 ml/kg, at 16.5C in 4.0-6.2 min): water (30 m0sm/kg), NaCl (70 mOsm/kg), NaCl + NaCitrate (270 mOsm/kg), NaCl + 9.7% glucose (650 mOsm/kg), and two commercial drinks containing various ionic and carbohydrate contents (380 and 390 mOsm/kg). Blood (20 ml/sample) was drawn at -5 min before and at +3, +9, +15, +30, and +70 min after drinking. Heart rate, blood pressures, and plasma renin activity, (Na+), (K+), (Osm), aldosterone, atrial natriuretic peptide, and epinephrine concentrations were unchanged after drinking. Post-drinking (PVP) decreased from 1.7 - 3.7 pg/ml within 3 min with all fluids independently of their composition, (Osm), or delta PV; with maximal depression to 0.1-0.7 pg/ml (p(0.05)) by 15 min. The continued (PVP) depression with all fluids from 15 to 70 min was accompanied by unchanged plasma (Osm) but 1.8-7.6% increases (p(0.05) in PV with 3) fluids (2 commercial and NaCitrate) and no change with the others. Percent changes in mean (PVP) and plasma norepinephrine concentrations (PNE) at 15 min correlated -0.70 (P(0.10)) suggesting that about half the variability in (PVP I I depression was associated with (PNE)). Thus, part of the mechanism for post-drinking (PVP) depression may involve a drinking stimulated norepinephrine (neural) factor.