Abstract P039: The Endogenous Ouabain And Changes In Blood Pressure And Sodium Excretion Following An Acute Saline Load In Essential Hypertension

Among ~25% of patients with essential hypertension (EH), circulating endogenous ouabain (EO) and aldosterone (Aldo) are typically coelevated and their BP is especially salt-sensitive (SS). We probed for exaggerated natriuresis in a large cohort (712) of hypertensive patients that underwent an acute 2hr (T 120 ) load with saline (0.9%/2 L). Results: Using a quartiles analysis of sodium excretion, the 4th quartile subgroups showed higher SBP and DBP at T 120 , and at 2 hrs recovery (T 240 ). Fractional sodium excretion (FE Na) was significantly higher during loading and recovery in the 4 th quartile subgroup. Plasma Aldo was suppressed after saline in all subgroups as expected. SS patients showed an increased EO. In the 4 th quartiles EO was elevated at baseline and after saline (see figure), p Manova > 0.001 and the urinary Na/K ratio output was higher. Further, increases in plasma Na + were greater in the 4 th quartile group (1.91 ± 0.15 vs 0.83 ± 0.13 mM, p<0.001). These data suggest circulating EO is a potential mediator of the exaggerated natriuresis in SS EH, and that this phenomenon is reminiscent of an “aldosterone escape”.

THE STUDY OF RENOPROTECTIVE PROPERTIES OF ERYTROPOETIN DERIVATIVES ON THE KIDNEY ISCHEMIA-REPERFUSION MODEL

Aim.The research was designed to study the renoprotective properties of erythropoietin derivatives on the kidney ischemiareperfusion experimental model.Materials and methods.The renoprotective properties of asialo erythropoietin (0.4 μg/kg and 2.4 μg/kg 30 minutes before the induction of ischemia) and carbamylated darbepoetin (50 μg/kg 24 hours before the ischemic stimulus) were studied in comparison with erythropoietin and darbepoetin in a series of experiments on male Wistar rats on a 40-minute bilateral model of renal ischemia-reperfusion. The renoprotective properties were evaluated by the results of biochemical markers of acute kidney injury, the dynamics of glomerular filtration rate and fractional sodium excretion, as well as the severity of microcirculatory disorders.Results.It was found that the prophylactic use of asialo erythropoietin (dose-dependent) and carbamylated darbepoetin leads to a decrease in the serum concentration of markers of acute renal damage, an increase in the glomerular filtration rate, a decrease in fractional sodium excretion, and a decrease in microcirculatory disorders.Conclusion.Asialo erythropoietin and carbamylated darbepoetin have the pronounced renoprotective properties and are the promising agents for the prevention and treatment of acute kidney injury.

Role of AQP1 in endotoxemia-induced acute kidney injury

The effect of endotoxemia (lipopolysaccharide, 2.5 mg/kg ip) was investigated in aquaporin (AQP) 1 knockout (KO) compared with wild-type (WT) mice. At baseline, KO mice exhibited higher water intake (WI) and urine output (UO). After endotoxemia, WI and UO remained higher in the KO than WT mice, and urine osmolality was lower. The higher serum osmolality in AQP1-KO mice during endotoxemia was associated with higher AQP2 (133 ± 8 vs. 100 ± 3%, P < 0.01), AQP3 (140 ± 8 vs. 100 ± 4%, P < 0.001) and Na+-K+-2Cl− cotransporter type 2 (NKCC2; 152 ± 14 vs. 100 ± 15%, P < 0.05) expression than that in WT mice. These responses during endotoxemia in the AQP1-KO mice compared with WT were associated with lower glomerular filtration rate (GFR) (69 ± 8 vs. 96 ± 8 ml/min, P < 0.05) and renal blood flow (0.77 ± 0.1 vs. 1.01 ± 0.1 ml/min, P < 0.01). Urinary sodium excretion and fractional sodium excretion were higher in KO compared with WT mice in endotoxemia and were accompanied by more severe tubular injury. With water repletion and comparable serum osmolalities, GFR was still lower in KO (57 ± 13 vs. 120 ± 6 ml/min, P < 0.01) compared with WT during endotoxemia. The abundance of AQP2 and AQP3 protein in KO mice was not different from WT mice; however, NKCC2, Na+/H+ exchanger type 3, and fractional sodium excretion remained higher in KO compared with WT. Thus the polyuria in AQP1-KO mice does not protect against endotoxemia-induced acute kidney injury but rather absence of AQP1 predisposed to enhanced endotoximic renal injury.