LAUSR

Purpose: Lens ion homeostasis is dependent on Na, K-ATPase and NKCC1. TRPV4 and TRPV1 channels, which are mechanosensitive, are known to regulate the activity of both these transporters. Here, we examined another mechanosensitive channel, piezo1, which also is expressed in the lens. Methods: Rubidium (Rb) uptake rate was measured as an index of inward potassium transport. Cytoplasmic calcium was measured using Fura-2. Hydrostatic pressure in cells at the lens surface was determined using a manometer-coupled microelectrode approach. Results: Rb uptake was increased in intact lenses (CTRL 2.0±0.3 vs Yoda1 3.3±0.5 nmoles/Kg lens dry wt., n=5, p<0.05) and cultured lens epithelium (CTRL 0.23±0.006 vs Yoda1 0.44±0.01 μmoles/mg protein/10 min, n=6, p<0.001) exposed to Yoda1, a piezo1 agonist. While most Rb uptake is Na, K-ATPase-dependent, there also is an NKCC-dependent component. In the presence of the Na, K-ATPase inhibitor ouabain, Yoda1 did not increase Rb uptake. However, Yoda1 increased Rb uptake similarly in the presence or absence of the NKCC inhibitor bumetanide. The Rb uptake response to Yoda1 was inhibited by a piezo1 antagonist GsMTx4 (5 μM) and also by nonselective stretch-activated channel antagonists, ruthenium red (50 μM) and gadolinium (50 μM). In intact lenses Yoda1 was observed to cause a pronounced but transient decrease of surface intracellular hydrostatic pressure. Yoda1 increased cytoplasmic calcium in isolated cultured lens epithelium (peak concentration: CTRL 181±53 vs Yoda1 683±194 nM, n=10, p<0.001). The calcium and Rb uptake responses to Yoda1 were absent in calcium-free bathing solution, consistent with calcium entry when piezo1 is activated. Conclusion: The findings point to stimulation of Na, K-ATPase, but not NKCC, when piezo1 is activated. Na, K-ATPase is the principal mechanism responsible for ion and water homeostasis in the lens. The functional role of lens piezo1 is a topic of further study. NIH (NEI) grant, R01EY029171 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.