FIGURE 8.

Adrenergic signaling and known effects on transporters involved in NaCl reabsorption in thick ascending limbs. Arrows indicate stimulation, and T-lines indicate inhibition. Dashed lines indicate that the complete signaling cascade is unknown. Relatively lower concentrations of norepinephrine (NE) are needed to stimulate α₂-receptors compared with β-receptors. Thus the red triangle representing NE is smaller. It is currently unclear how β-receptors activate mitogen-activated protein kinase (MAPK) in thick ascending limbs. It is also unclear how they activate Na⁺-K⁺-2Cl⁻ cotransporter type 2 (NKCC2). α₂R: α₂-adrenergic receptor; βR, β-adrenergic receptor; NKCC2, Na⁺-K⁺-2Cl⁻ cotransporter type 2; NO, nitric oxide; NOS3, NO synthase type 3; PI3K, phosphatidylinositol 3-kinase; PKA, cAMP-dependent protein kinase.