Renal regulation of water homeostasis is complex and involves diverse hormones, but crosstalk among their distinct signaling pathways is not well understood. A major player is vasopressin (VP), which increases cellular cAMP, activates protein kinase A, and changes aquaporin-2 (AQP2) phosphorylation. AQP2 membrane accumulation in kidney principal cells increases collecting duct (CD) water permeability and urine concentration. We showed that the epidermal growth factor receptor (EGFR) inhibitor Erlotinib mimics the effect of VP on AQP2 trafficking and water permeability and that EGF inhibits VP-induced CD water permeability by reducing AQP2 phosphorylation and preventing membrane accumulation. Interestingly, betacellulin, a member of the EGF family, also has a diuretic effect in rats. To examine the role of EGF and betacellulin on urine concentration, we implanted osmotic minipumps delivering EGF, betacellulin or control solution into male mice that lack EGF (EGF-/- mice). 12-week-old EGF-/- mice produce less urine that is more hypertonic than in wild-type mice (2443 ± 383 mOsm/kg (n=43) vs 1843 ± 465 (n=27)). In contrast, their serum osmolarity was similar 330 ± 11 (n=31) vs 329 ± 14 (n=48) mOsm/kg, as well as their serum copeptin levels (15.8 ± 7.6 (n=9) to 12.8 ± 4.3 ng/ml (n=10), a surrogate for vasopressin. Immunofluorescence revealed more AQP2 expression in principal cells, while no change in EGFR expression was seen. The EGFR was mainly expressed in basolateral membranes of principal cells as well as the apical membrane, especially in the inner medulla. Western blots of total kidney lysates showed that EGF depletion affects expression of proteins regulating water and salt reabsorption. EGF-/- mice express significantly more AQP2 than wild-type (144 % ± 34 vs 100 % ± 25, (n=18), p< 0.0001), AQP3 (175 % ± 81 vs 100 % ± 22, (n=18), p=0.0005) and AQP4 (175 % ± 34 vs 100 % ± 27,(n=18), p =0.004). Expression of Na/K-ATPase and NKCC2 increased, while no change in the sodium chloride cotransporter (NCC) was observed. Finally, male EGF-/- mice were implanted with minipumps delivering EGF, betacellulin, or vehicle. After 3 days, urine volume increased 2-fold (0.67 ± 0.46 to 1.13 ± 0.57 ml, (n=10), p=0.04), and urine osmolarity was reduced 2.3-fold (6228 ± 2039 to 2727 ± 518 mOsm/kg, (n=10), p< 0.001). Betacellulin administration also increased urine volume 2-fold, and reduced osmolality from 5448 ± 514 to 2895 ± 729 mOsm/kg, (n=6), p=0.01. These results suggest that EGF plays an important regulatory role in VP-induced water reabsorption. Its absence results in increased expression of aquaporins and other ion transporters that regulate urine concentration, likely resulting from the unopposed action of VP on protein expression and membrane trafficking. In the absence of EGF, betacellulin may also play a role in regulating urine concentration. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
Bouley et al. (Fri,) studied this question.