Endogenous dopamine modulates jejunal sodium absorption during high-salt diet in young but not in adult rats.
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.
Finkel
Y
Y
Department of Woman and Child Health, Karolinska Institutet St. Göran's Children's Hospital, Stockholm, Sweden.
Eklöf
A C
AC
Granquist
L
L
Soares-da-Silva
P
P
Bertorello
A M
AM
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*
D002395:Catecholamines; D012964:Sodium; D004298:Dopamine