Jejunal dopamine and Na,K-ATPase activity in early chronic renal insufficiency.
OBJECTIVE
The uninephrectomised and three-quarter nephrectomised (3/4nx) rats present dopamine-sensitive enhanced natriuresis. This is accompanied in uninephrectomised rats by a reduced jejunal Na(+),K(+)-ATPase activity with recovered sensitivity to inhibition by dopamine. The present study examined the jejunal Na(+),K(+)-ATPase activity and the role of dopamine in 3/4nx animals.


METHODS
Fourteen days after surgery, the L-amino acid decarboxylase activity (AADC) activity, the enzyme responsible for the synthesis of dopamine, and the Na(+),K(+)-ATPase activity, were determined in jejunal epithelial cells from 3/4nx and Sham rats. In addition, the effect of dopamine (1 micromol/L) on jejunal Na(+),K(+)-ATPase activity was evaluated in both groups.


RESULTS
The 3/4nx rats presented a reduced AADC activity in jejunal epithelial cells (V(max) in nmol/mg prot/15 min, 142 +/- 6 vs 190 +/- 10, P < 0.05). In addition, the jejunal Na(+),K(+)-ATPase activity was increased in 3/4nx rats (Pi release in nmol/mg prot/min, 137 +/- 1 vs 122 +/- 2, P < 0.05). However, dopamine was unable to inhibit the Na(+),K(+)-ATPase activity in jejunal epithelial cells from both 3/4nx and Sham animals.


CONCLUSIONS
In contrast to uninephrectomy, the jejunal Na(+),K(+)-ATPase activity is increased in 3/4nx rats and is not sensitive to inhibition by dopamine.
Sampaio-Maia
Benedita
B
Institute of Pharmacology and Therapeutics, Porto, Portugal.
Serrao
Paula
P
Moura
Manuela
M
Pestana
Manuel
M
D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D004298:Dopamine / Q000502:physiology*; D007583:Jejunum / Q000201:enzymology*; D008297:Male; D009392:Nephrectomy; D051381:Rats; D017208:Rats, Wistar; D051436:Renal Insufficiency, Chronic / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D001142:Aromatic-L-Amino-Acid Decarboxylases; D000254:Sodium-Potassium-Exchanging ATPase; D004298:Dopamine