Comparative study on sodium transport and Na+,K+-ATPase activity in Caco-2and rat jejunal epithelial cells: Effects of dopamine

The present study reports on the effects of dopamine on sodium transepithel ial transport and Na+,K+-ATPase activity in Caco-2 cells, a human epithelia l intestinal cell line which undergoes enterocyte differentiation in cultur e, and jejunal epithelial cells from 20 day old Wistar rats. Addition of am photericin B to the mucosal side stimulated I-sc in a concentration depende nt manner (Caco-2 cells, EC50=0.9 [0.5, 1.7] muM; rat jejunum, EC50=7.4 [0. 8; 70.1] muM). The presence of 1 muM dopamine did not change the effect of amphotericin B in Caco-2 cells, but produced a significant (P <0.05) decrea se in the maximal effect of amphotericin B in the rat jejunum. Dopamine (1 muM), added to the serosal side, did not change the I-sc profile in Caco-2 cells, but produced a significant increase in the (mu)rat jejunum. This eff ect was antagonized by SKF 83566 (1 muM), but not S-sulpiride (1 muM), and was mimicked by SKF 38393 (10 nM), but not by quinerolane (10 nM). Basal Na +, K+-ATPase activity (in nmol Pi mg protein(-1) min(-1)) in Caco-2 cells ( 49.5 +/-0.2) was similar to that observed in isolated rat jejunal epithelia l cells (52.3 +/-3.4). Dopamine (1 muM) significantly (P <0.05) decreased N a+, K+-ATPase activity in rat jejunal epithelial cells, but failed to inhib it Na+,K+-ATPase in Caco-2 cells. This effect of dopamine was antagonized b y SKF 83566 (1 M), but not S-sulpiride (1 muM), and was mimicked by SKF 383 93 (10 nM), but not by quinerolane (10 muM). The specific binding of [H-3]- Sch 23390 to the rat intestinal mucosa was saturable with an apparent disso ciation constant (K-D) of 2.4 (0.4; 4.5) nM and maximum receptor density of 259.8 +/- 32.6 fmol/mg protein. No significant specific binding of [H-3]-S ch 23390 was observed in membranes from Caco-2 cells. In conclusion, the re sults obtained show that D-1-like receptor mediated effects of dopamine in the rat jejunum on sodium absorption are absent in Caco-2 cells, most proba bly because this cell line does not express DI-like dopamine receptors, whi ch ultimately are responsible for the inhibitory effect of the amine upon i ntestinal Na+,K+-ATPase. (C) 2001 Elsevier Science Inc. All rights reserved .