Microgravity significantly impacts fluid redistribution in the human body, and vasopressin (AVP) plays a crucial, yet complex, role in this process. Under chronic adaptation to microgravity, astronauts typically experience a reduction in total body water, plasma volume, and extracellular fluid volume due to several factors, including altered renal function. In the kidney collecting duct, AVP increases water reabsorption by redistribution of aquaporin-2 (AQP2) water channels. To evaluate the brain-kidney interplay in microgravity at cellular levels, mouse hypothalamic mHypoA-2/28 cells derived from the supraoptic nucleus (SON) and found to express the AQP4 water channel as in native cells, were exposed to simulated microgravity using the Random Positioning Machine (RPM) for 24 h in a hyperosmolar medium, to simulate the physiological stimulus for AVP release. This treatment resulted in a significant increase in AVP mRNA levels. Collecting duct MCD4 cells exposed to the cell culture medium collected from mHypoA-2/28, displayed a significant enrichment of AQP2 in the plasma membrane fraction, confirming AQP2 redistribution in response to actual AVP released from mHypoA-2/28 cells. In line, MCD4 cells exposed to microgravity had a significant higher rate of AQP2-expressing exosome release in the medium, suggesting that microgravity stimulates AQP2 recycling. Together these data indicate that microgravity promotes AVP release from SON thus activating the vasopressin-AQP2 axis. 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.
Centrone et al. (2026) studied this question.