title: Endogenous dopamine modulates jejunal sodium absorption during high-salt diet in young but not in adult rats.
abstract: OBJECTIVE
  This study was designed to investigate the contribution of endogenous catecholamines to the regulation of small intestinal sodium transport during postnatal development.
  
  
  METHODS
  Jejunal permeability was determined by a constant perfusion, nonabsorbable marker technique in weanling, adolescent, and adult rats fed either a high-salt diet or normal-salt diet. Tissue catecholamine levels were determined by high-performance liquid chromatography with electrochemical detection.
  
  
  RESULTS
  In 20-day-old but not in 40-day-old rats, a significantly lower net sodium absorption was observed during high-salt diet compared with age-matched controls on normal-salt diet. Inhibition of dopamine synthesis significantly increased the net sodium absorption in 20-day-old rats on high-salt diet compared with untreated 20-day-old rats on high-salt diet. The basal levels of dopamine in 20-day-old rats were twofold higher than in 40-day-old rats. During high-salt diet, both age groups responded with an increase in dopamine production. Norepinephrine levels were significantly higher (30-fold) in 20-day-old rats than in 40-day-old rats, but norepinephrine content was not significantly changed during high-salt diet in either groups.
  
  
  CONCLUSIONS
  The results indicate that weanling animals have a greater jejunal sodium absorption than older animals, probably because of higher noradrenergic tonus. A challenge with a high-salt diet results in a decrease of the intestinal sodium absorption in weaning rats but not in adult rats; endogenous dopamine appears to play an important role in this regulation.
authors.affiliation: Department of Woman and Child Health, Karolinska Institutet St. Göran's Children's Hospital, Stockholm, Sweden.
authors.forename: Y
authors.initials: Y
authors.lastname: Finkel
authors.forename: A C
authors.initials: AC
authors.lastname: Eklöf
authors.forename: L
authors.initials: L
authors.lastname: Granquist
authors.forename: P
authors.initials: P
authors.lastname: Soares-da-Silva
authors.forename: A M
authors.initials: AM
authors.lastname: Bertorello
mesh_terms: D000042:Absorption; D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001692:Biological Transport; D002395:Catecholamines / Q000378:metabolism; D004039:Diet, Sodium-Restricted; D004298:Dopamine / Q000502:physiology*; D007413:Intestinal Mucosa / Q000378:metabolism; D007583:Jejunum / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000493:pharmacokinetics*
chemical_list: D002395:Catecholamines; D012964:Sodium; D004298:Dopamine