D3 dopamine receptor regulation of D5 receptor expression and function in renal proximal tubule cells

results with quantitative real time RT-PCR and Northern Blot. Blood pressure was measured to determine the time of development of hypertension. Results: Among the 10,000 genes examined, we found that expression of the human gene homolog FXYD domain containing ion transport regulator 5 (FXYD5)was downregulated in thekidneys and second-order mesenteric arteries of SHR. FXYD5 expression was 14.8fold lower in SHR than in WKY rats (P<0.01). Northern blot results indicated that expression of FXYD5 occurred in a timeand tissuedependent manner. FXYD5 expression did not differ between SHR and WKY rats at 4 and 8 weeks of age, but FXYD5 mRNA levels were significantly lower in SHR by 13 weeks of age (P<0.01). Peak FXYD5 expression was seen at 8 weeks in SHR and at 13 weeks in WKY rats. Conclusion: The FXYD5gene,which is involved in the induction ofNa, KATPase activity, was significantly suppressed in SHR. This downregulation may have a profound effect on blood pressure regulation. Thus, FXYD5 may serve as a potential target for antihypertensive therapy.