title: Enhanced renal Na+ reabsorption by carbohydrate in beverages during restitution from thermal and exercise-induced dehydration in men.
abstract: We examined whether carbohydrate in beverages accelerated fluid retention during recovery from thermal and exercise-induced dehydration and whether it was caused in part by an enhanced renal Na+ reabsorption rate due to insulin secretion. After dehydrating by ∼2.3% body weight by exercise in a hot environment, seven young men underwent high-carbohydrate, low-carbohydrate, or control rehydration trials by drinking one of three beverages with 3.4 g glucose + 3.1 g fructose, 1.7 g glucose + 1.6 g fructose, or 0.0 g glucose + 0.0 g fructose per deciliter, respectively, in a common composition of electrolyte solution: 21 meq/l [Na+], 5 meq/l [K+], 16.5 meq/l [Cl-], 10 meq/l [citrate(-3)]. They drank the same amount of beverage as total body weight loss within 30 min. During the 60 min before the start of drinking and the following 180 min, we measured plasma volume (PV), plasma glucose ([Glc]p), serum insulin ([Ins]s), plasma Na+ concentrations, and the renal clearances of inulin, lithium, and Na+ with plasma vasopressin ([AVP]p) and aldosterone concentrations ([Ald]p) every 30 min. After dehydration, PV decreased by ∼5% and plasma osmolality increased by ∼6 mosmol/kg H2O in all trials with no significant differences among them. We found in the high-carbohydrate trial that 1) PV increased faster than in the control trial and remained at the higher level than other trials for the last 60 min (P < 0.05); 2) accumulated urine volume was smallest after 90 min (P < 0.05); 3) the renal Na+ reabsorption rate was greatest for the first 120 min (P < 0.05); 4) during which period [AVP]p and [Ald](p) were not significantly different from other trials (both, P > 0.9); and 5) [Glc](p) and [Ins]s were highest from 45 to 105 min (P < 0.05) during rehydration. Thus carbohydrate in beverages enhances renal Na+ reabsorption, and insulin is possibly involved in this enhancement.
authors.affiliation: Dept. of Sports Medical Sciences, Institute of Pathogenesis and Disease Prevention, Shinshu Univ. Graduate School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan.
authors.forename: Yoshi-Ichiro
authors.initials: Y
authors.lastname: Kamijo
authors.forename: Shigeki
authors.initials: S
authors.lastname: Ikegawa
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Okada
authors.forename: Shizue
authors.initials: S
authors.lastname: Masuki
authors.forename: Kazunobu
authors.initials: K
authors.lastname: Okazaki
authors.forename: Koji
authors.initials: K
authors.lastname: Uchida
authors.forename: Masao
authors.initials: M
authors.lastname: Sakurai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nose
mesh_terms: D000328:Adult; D000450:Aldosterone / Q000097:blood; D000704:Analysis of Variance; D001628:Beverages; D001642:Bicycling; D015415:Biomarkers / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D003681:Dehydration / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism*; D004777:Environment; D015444:Exercise; D005080:Exercise Test; D005632:Fructose / Q000008:administration & dosage / Q000378:metabolism*; D005919:Glomerular Filtration Rate; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism*; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D007328:Insulin / Q000097:blood; D007564:Japan; D007684:Kidney Tubules / Q000378:metabolism* / Q000503:physiopathology; D016018:Least-Squares Analysis; D008297:Male; D009318:Natriuresis; D009481:Neurophysins / Q000097:blood; D009994:Osmolar Concentration; D010953:Plasma Volume; D011498:Protein Precursors / Q000097:blood; D020127:Recovery of Function; D015532:Rehydration Solutions / Q000008:administration & dosage / Q000378:metabolism*; D012964:Sodium / Q000097:blood / Q000378:metabolism*; D013997:Time Factors; D014563:Urodynamics; D014667:Vasopressins / Q000097:blood; D014882:Water-Electrolyte Balance; D055815:Young Adult
chemical_list: C438657:AVP protein, human; D015415:Biomarkers; D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin; D009481:Neurophysins; D011498:Protein Precursors; D015532:Rehydration Solutions; D014667:Vasopressins; D005632:Fructose; D000450:Aldosterone; D012964:Sodium; D005947:Glucose