Renal Dopamine Receptor Signaling Mechanisms in Spontaneously Hypertensive and Fischer 344 Old Rats

Abstract

Dopamine plays an important role in the regulation of renal sodium excretion. The activation of D₁-like receptors located on the proximal tubules causes inhibition of tubular sodium reabsorption by inhibiting Na, H-exchanger and Na, K-ATPase activity. The D₁-like receptors are linked via G proteins to the multiple cellular signaling systems namely adenylyl cyclase and phospholipase C (PLC). A defective renal dopamine receptor function exists in spontaneously hypertensive rats (SHR). In the proximal tubules of SHR, the stimulation of adenylyl cyclase and PLC caused by dopamine was significantly reduced in comparison with Wistar-Kyoto (WKY) rats. Also unlike the effects seen in WKY, D₁-like receptor activation did not inhibit Na, K-ATPase and Na, H-exchanger activities in SHR. In addition, reduced quantity of Gq/11α proteins was detected in the basolateral membranes of SHR compared to WKY rats. Studies revealed that there may be a primary defect in D₁-like receptors leading to an altered signaling system in the proximal tubules and reduced dopamine-mediated effect on renal sodium excretion in SHR. Recently, it has been shown that the disruption of D_1A receptors at the gene level causes hypertension in mice. Similar to SHR, dopamine and D₁-like receptor agonist failed to inhibit Na, K-ATPase activity in the proximal tubules of old Fischer 344 rats. Unlike the observations in SHR where D₁-like receptors were

Key Words:

• Dopamine
• dopamine receptors
• proximal tubules
• kidney
• hypertension
• aging