Figure 10.

Segmental accounting of whole kidney ${\text{NH}}_4^{+}$ flows (delivery) and fluxes (transport), in hyperkalemia, with tubuloglomerular feedback (TGF) fixed at its normokalemic value (A1). Negative or positive transport values correspond to reabsorptive or secretory fluxes. As in Fig. 8, open bars denote unregulated hyperkalemia (HK + no TGF; A3); backslash bars indicate aldosterone (Aldo) action, a doubling of the density of the epithelial Na⁺ channel and Na⁺-K⁺-ATPase in principal cells (HK + no TGF + Aldo; C1); forward slash bars adds an 80% reduction in NaCl cotransporter density (HK + no TGF + Aldo-NCC; C2); and cross-hatched bars add a halving of ammoniagenesis (HK + no TGF + Aldo-NCC-Amm; C3). The values shown are those in Table 9. Halving of ammoniagenesis is evident in the reduced ${\text{NH}}_4^{+}$ secretion in the proximal convoluted tubule (PCT) and distal convoluted tubule (DCT), and urinary ${\text{NH}}_4^{+}$ excretion has normalized (comparing A1). CD, collecting duct; CNT, connecting duct; LOH, loop of Henle.