Concerted action of dopamine on renal and intestinal Na⁺-K⁺-ATPase in the rat remnant kidney

Abstract

The present study evaluated renal and intestinal adaptations in sodium handling in uninephrectomized (Unx) rats and the role of dopamine. Two weeks after uninephrectomy, the remnant kidney in Unx rats weighed 33 +/- 2% more than the corresponding kidney in sham-operated (Sham) animals. This was accompanied by increases in urinary levels of dopamine and major metabolites [3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid] and increases in maximal velocity values (169 vs. 115 nmol. mg protein(-1). 15 min(-1)) for renal aromatic L-amino acid decarboxylase, the enzyme responsible for the synthesis of renal dopamine. High salt (HS) intake increased (P < 0.05) the urinary excretion of dopamine and DOPAC in Unx and Sham rats. However, the urinary levels of L-3,4-dihydroxyphenylalanine, dopamine, and DOPAC in Sham rats during HS intake were lower than in Unx rats. Blockade of dopamine D(1) receptors (Sch-23390, 2 x 30 microg/kg) reduced the urinary excretion of sodium in Unx (31% decrease) more pronouncedly than in Sham (19% decrease) rats. However, inhibition of renal Na(+)-K(+)-ATPase activity by dopamine was of similar magnitude in Unx and Sham rats. In parallel, it was observed that uninephrectomy resulted in a significant reduction in jejunal sodium absorption and Na(+)-K(+)-ATPase activity in jejunal epithelial cells. In jejunal epithelial cells from Sham rats, dopamine (1 microM) failed to inhibit Na(+)-K(+)-ATPase activity, whereas in Unx rats it produced a significant reduction. It is concluded that uninephrectomy results in increased renal dopaminergic activity and dopamine-sensitive enhanced natriuresis. Furthermore, it is suggested that decreased jejunal absorption of sodium may take place in response to partial renal ablation, as an example of renal-intestinal cross talk.

Opposite sexual dimorphism of 3,4-dihydroxyphenylalanine decarboxylase in the kidney and small intestine of mice

“…In fact, an alternate view on the effect of this hormone on intestinal DDC is that it may be secondary to its action on the kidney. This possibility seems to be consistent with the existence of a renal-intestinal crosstalk, as it was earlier suggested (Vieira-Coelho et al 2000), although the mechanisms that support this possibility are far from being understood. The fact that in our ontogeny studies (Figs 2B and 4B) DDC sex dimorphism in the duodenum appears to be delayed with respect to that found in the kidney could also support the hypothesis that primary changes in DDC in the kidney may affect later the expression of this enzyme in the intestine.…”

“…Since dopamine, a product of DDC, has been implicated in renal sodium handling in the rat (Vieira-Coelho et al 2000), we decided to study the possible influence of DDC dimorphism in kidney on sodium renal absorption by measuring sodium levels in the urine of male and female mice. Table 2 shows that the relative sodium excretion in the urine of female mice was about 60% higher than in male mice.…”

“…In fact, it has been reported that in young rats fed with a high-salt diet, jejunal Na C /K C ATPase is inhibited, likely by the action of locally formed dopamine (Vieira-Coelho et al 1998). Moreover, decreased jejunal absorption of sodium may take place in response to partial renal ablation (Vieira-Coelho et al 2000). Therefore, a greater inhibition of Na C uptake in the intestinal mucosa of male mice, as a consequence of a higher dopamine production, could be associated with relatively higher levels of Na C in the feces of male mice.…”

“…However, several studies have pointed out that the enzyme may participate in the regulation of different physiological processes in peripheral tissues. Thus, in the rat kidney, it has been suggested that tubular DDC and its product dopamine may affect sodium absorption by renal epithelial cells (Bertorello et al 1988, Vieira-Coelho et al 2000. In the mouse, the high DDC activity found in the pancreatic islets has been related with a stimulatory effect on insulin secretion (Lindström 1986).…”

Dopamine, hypertension and obesity

“…35 The inhibition of the jejunum Na + /K + /ATPase pump, under sodium overload conditions, is also observed in adult animals after ablation of one of their kidneys, which would mean a possible DA-induced connection between kidney and intestine. 36 …”