Fig. 4.
Synthesis and actions of ET-1 in the proximal tubule. ET-1 production is enhanced during inflammation, hypoxia, glomerular injury, and acidemia. Most studies implicate ETB in mediating ET effects on the proximal tubule, although ETA activation may result in inhibition of Na reabsorption. ETB effects appear to depend on the concentration of ET-1, with lower concentrations stimulating Na transport processes and higher concentrations having the opposite effect. It is likely that ET-1 exerts primarily a natriuretic effect on the proximal tubule under physiological conditions. See text for definitions.
