Renal proximal tubules secrete various organic anions, including drugs and
p-aminohippurate (PAH). Uptake of PAH from blood into tubule cells occurs b
y exchange with intracellular alpha -ketoglutarate and is mediated by the o
rganic anion transporter 1. PAH exit into tubule lumen is species specific
and may involve ATP-independent and -dependent transporters.