Ionic transport in macula densa cells Jean-Yves Lapointe, Anuar Laamarti, P. Darwin Bell  Kidney International  Volume 54, Pages S58-S64 (September 1998) DOI: 10.1046/j.1523-1755.1998.06712.x Copyright © 1998 International Society of Nephrology Terms and Conditions

Figure 1 Transport model for macula densa (MD) cells. Kidney International 1998 54, S58-S64DOI: (10.1046/j.1523-1755.1998.06712.x) Copyright © 1998 International Society of Nephrology Terms and Conditions

Figure 2 Estimation of intracellular [Na+] ([Na+]i) in the presence of Na:K:2Cl cotransport. Upper panel depicts equilibrium of the apical Na:H exchanger with a high rate of Na:K:2Cl cotransport elevating [Na+]i. Lower panel shows the effect of luminal [Cl-] ([Cl-]L) on intracellular pH (pHi) in the presence or the absence of amiloride. Note that in the presence of 140mm [Cl-]L, amiloride had no effect on pHi. The data are taken from8. Kidney International 1998 54, S58-S64DOI: (10.1046/j.1523-1755.1998.06712.x) Copyright © 1998 International Society of Nephrology Terms and Conditions

Figure 3 Estimation of intracellular [Na+] ([Na+]) in the absence of Na:K:2Cl cotransport. Upper panel shows the observed H+ efflux mediated by the apical Na:H exchanger when the Na:K:2Cl cotransporter is blocked by furosemide. Lower panel depicts the furosemide-induced cell alkalization and the large acidification caused by 1mm luminal amiloride, showing that the apical Na:H exchanger generates a significant H+ efflux in the presence of furosemide. Data are taken from8. Kidney International 1998 54, S58-S64DOI: (10.1046/j.1523-1755.1998.06712.x) Copyright © 1998 International Society of Nephrology Terms and Conditions

Figure 4 Averaged pHi time courses following luminal addition of 20mm NH4+. The noisy traces represent averaged pHi recordings from five different macula densa (MD) plaques exposed to 20mm [NH4+]L under four different experimental conditions: control (A, 25mm [NaCl]L, 5mm [K+]L), in the presence of 5mm Ba2+ (B), in the presence of 5 μm bumetanide (C), and in the presence of both inhibitors simultaneously (D). The smooth traces represent a satisfactory fit obtained from our computer model. For the four panels, apical and basolateral NH3 permeability coefficients were both set at 20s-1, and the pH sensitivity (SH, see text) of the pH-regulating system was set at 3.7mm s-1. The apical permeability coefficient for NH4+ entry was set at 0.68, 0.50, 0.42, and 0.05s-1, and the permeability coefficient for NH4+ efflux through both apical and basolateral membranes was set at 0.25, 0.18, 0.28, and 0.10s-1 for A, B, C, and D, respectively. Initial NH4+ influx rates (JNH4) are calculated using the given coefficients. Kidney International 1998 54, S58-S64DOI: (10.1046/j.1523-1755.1998.06712.x) Copyright © 1998 International Society of Nephrology Terms and Conditions

Figure 5 Expected effects of an increase in luminal [NaCl] on macula densa cells intracellular parameters. Kidney International 1998 54, S58-S64DOI: (10.1046/j.1523-1755.1998.06712.x) Copyright © 1998 International Society of Nephrology Terms and Conditions