Progression of anemia and its relationship with renal function, blood pressure, and erythropoietin in rats with chronic kidney disease

Background: In chronic kidney disease (CKD), anemia and hypertension are significant co-morbidities that contribute to cardiovascular and renal disease progression. Objective: The purpose of the study was to identify correlations between changes in hematologic variables against markers of renal function, blood pressure, and erythropoietin (EPO) in a naturally occurring hypertensive model of CKD, the Lewis polycystic kidney (LPK) rat. Methods: Complete blood count, systolic blood pressure, urea and creatinine concentration, urinary protein to creatinine ratio, and plasma EPO concentration were determined in control Lewis (n = 51) and LPK rats (n = 56) aged 6-24 weeks. Renal EPO gene expression and RBC osmotic fragility were also documented. Hematopoiesis in spleen and bone marrow were assessed. Results: Lewis polycystic kidney rats had increasing urea and creatinine concentrations, concurrent with the development of a nonregenerative normocytic/normochromic anemia and hypertension, with a significant negative correlation between both HGB and HCT with urea concentration and blood pressure (P < .01). HCT was also significantly negatively correlated with creatinine concentration (P = .014). WBC was significantly negatively correlated with urea (P < .01). Plasma EPO concentration was increased and renal EPO mRNA expression was significantly upregulated in LPK animals. The former was significantly positively correlated with blood pressure and platelet count (P < .05). RBC osmotic fragility was normal in LPK rats and there was no evidence for increased RBC elimination or extramedullary hematopoiesis. Conclusions: Marked anemia in the LPK CKD rodent model in the presence of elevated EPO suggests inefficient erythropoiesis that is correlated with plasma urea concentration and blood pressure.