Numerous studies have demonstrated that angiotensin II (ANG II) is involved in hypertension and renal changes occurring as a consequence of an adverse event during renal development. However, it was unknown whether this involvement is sex and age dependent. This study examines whether the increments in arterial pressure (AP) and in the renal sensitivity to ANG II are sex and age dependent in rats with altered renal development. It also evaluates whether the ANG II effects are accompanied by increments in AT(1) receptors and oxidative stress. Experiments were performed in 3- to 4- and 10- to 11-mo-old rats treated with vehicle or an AT(1) receptor antagonist (ARAnp) during the nephrogenic period. ARAnp-treated rats were hypertensive, but an age-dependent rise in AP was only found in males. Three days of treatment with candesartan (7 mg·kg(-1)·day(-1)) led to a fall of AP that was greater (P < 0.05) in male than in female 10- to 11-mo-old ARAnp-treated rats. Oxidated proteins were elevated (P < 0.05), and the decrease in AP elicited by candesartan was reduced (P < 0.05) when these rats are also treated with tempol (18 mg·kg(-1)·day(-1)). Hypertension was not maintained by an elevation of AT(1) receptors in kidneys and mesenteric arteries. The acute renal hemodynamic response to ANG II (30 ng·kg(-1)·min(-1)) was similarly enhanced (P < 0.05) in both sexes of ARAnp-treated rats at 3-4 but not at 10-11 mo of age. Our results suggest that an adverse event during the nephrogenic period induces an ANG II-dependent increment in AP that is aggravated only in males during aging and that oxidative stress but not an increase in AT(1) receptor contributes to the rise in AP. This study also shows that the renal hemodynamic sensitivity to ANG II is transitorily enhanced in both sexes of rats with altered renal development.

.-The function of the NaPiIIa renal sodium-phosphate transporter is regulated through a complex network of interacting proteins. Several PDZ domain-containing proteins interact with its COOH terminus while the small membrane protein MAP17 interacts with its NH 2 end. To elucidate the function of MAP17, we identified its interacting proteins using both bacterial and mammalian two-hybrid systems. Several PDZ domain-containing proteins, including the four NHERF proteins, as well as NaPiIIa and NHE3, were found to bind to MAP17. The interactions of MAP17 with the NHERF proteins and with NaPiIIa were further analyzed in opossum kidney (OK) cells. Expression of MAP17 alone had no effect on the NaPiIIa apical membrane distribution, but coexpression of MAP17 and NHERF3 or NHERF4 induced internalization of NaPiIIa, MAP17, and the PDZ protein to the trans-Golgi network (TGN). This effect was not observed when MAP17 was cotransfected with NHERF1/2 proteins. Inhibition of protein kinase C (PKC) prevented expression of the three proteins in the TGN. Activation of PKC in OK cells transfected only with MAP17 induced complete degradation of MAP17 and NaPiIIa. When lysosomal degradation was prevented, both proteins accumulated in the TGN. When the dopamine D1-like receptor was activated with fenoldopam, both NaPiIIa and MAP17 also accumulated in the TGN. Finally, cotransfection of MAP17 and NHERF3 prevented the adaptive upregulation of phosphate transport activity in OK cells in response to low extracellular phosphate. Therefore, the interaction between MAP17, NHERF3/4, and NaPiIIa in the TGN could be an important intermediate or alternate path in the internalization of NaPiIIa. phosphate transport; PDZ; PDZK1; protein interaction; opossum kidney cells RENAL REABSORPTION OF INORGANIC phosphate (P i ) and its regulation involve molecular mechanisms more complicated than initially thought. After expression cloning of NaPiIIa (24), the transporter responsible for most renal P i reabsorption, a complex network of interacting proteins that modulate the activity of this transporter has been described (for reviews, see Refs. 4,5,15,35).Most of the proteins that interact with this transporter contain one or more PDZ domains (acronym of the postsynaptic density protein PSD-95, the Drosophila junctional protein Disc-large, and the tight junction protein ZO1). These domains consist of 80 -90 amino acids that very often (but not always) scaffold specific proteins into supramolecular complexes (17). Several PDZ domain-containing proteins interact with the COOH end of NaPiIIa (12) DD96/SPAP is a small membrane protein that interacts with the NH 2 terminus of the phosphate transporter (28). MAP17 was first identified by differential display because its RNA was overexpressed in several carcinomas (18). In addition, it was also isolated during the expression cloning of a renal Na/D-mannose cotransport in Xenopus laevis oocytes, and it was considered to be an activator of a mannose transporter endogenous to the oocyte (6). Yeast two-hybrid experi...

AMP-activated kinase (AMPK) controls cell energy homeostasis by modulating ATP synthesis and expenditure. In vitro studies have suggested AMPK may also control key elements of renal epithelial electrolyte transport but in vivo physiological confirmation is still insufficient. We studied sodium renal handling and extracellular volume regulation in mice with genetic deletion of AMPK catalytic subunits. AMPKα1 knockout (KO) mice exhibit normal renal sodium handling and a moderate antidiuretic state. This is accompanied by higher urinary aldosterone excretion rates and reduced blood pressure. Plasma volume, however, was found to be increased compared with wild-type mice. Thus blood volume is preserved despite a significantly lower hematocrit. The lack of a defect in renal function in AMPKα1 KO mice could be explained by a compensatory upregulation in AMPK α2-subunit. Therefore, we used the Cre-loxP system to knock down AMPKα2 expression in renal epithelial cells. Combining this approach with the systemic deletion of AMPKα1 we achieved reduced renal AMPK activity, accompanied by a shift to a moderate water- and salt-wasting phenotype. Thus we confirm the physiologically relevant role of AMPK in the kidney. Furthermore, our results indicate that in vivo AMPK activity stimulates renal sodium and water reabsorption.

AMP‐activated kinase (AMPK) regulates cell energy balance by modulating ATP synthesis and consumption. In epithelia, AMPK interacts with and regulate ion transport systems, including CFTR, ENaC and NKCC. We studied renal function and measured blood pressure in mice with genetic deletion of the alpha‐1 catalytic subunit of AMPK (a1KO mice; C57Bl6J background). When fed a standard diet (0.3%NaCl) a1KO mice showed mild antidiuresis (WT=0.053 vs. KO=0.038 mL/d/g bw). No significant differences in glomerular filtration rate, sodium or potassium handling were found. When fed low Na+ (0.02%) or high salt (4%NaCl) diets, a1KO mice achieved ion and water balance. Lack of aversion for the high salt diet in a1KO mice suggested increased sodium appetite. Aldosterone urinary excretion was consistently higher in a1KO mice (WT=0.028 vs. KO=0.037 ng/d/g bw). Telemetric 24h blood pressure records showed significantly lower blood pressure in a1KO mice, especially nocturnal diastolic pressure (WT=93.5 vs. KO=86.1 mmHg). We found that a1KO mice lose water and sodium in their feces compared to wild‐type mice. In the kidney, we observed up‐regulation of the alpha‐2 catalytic subunit, which may provide functional compensation for the loss of alpha‐1 activity. Thus, kidneys from a1KO mice apparently have normal function and may be actually compensating for extra renal water and ion losses.MICIIN Spain BFU2007/62119