Acute and chronic temperature dependence of Na+/H+ exchange activity of Pimephales promelas gills

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2021-07, Vol.257, p.110975-110975, Article 110975
• Main Authors: Ye, William, Patel, Jill, Thede, Katrina, Aravindabose, Varsha, Wentworth, Simon, Monroe, Ian, Garvin, Matthew L., Garvin, Jeffrey L., Packer, Randall K.
• Format: Article
• Language: English
• Subjects: Acclimatization - physiology; Ammonium; Ammonium Compounds - chemistry; Animals; Cold Temperature; Cyprinidae - metabolism; Cyprinidae - physiology; Fresh Water; Gills - physiology; Homeostasis; Kinetics; Na absorption; Na transport; Osmolar Concentration; Potassium - chemistry; RNA, Messenger - metabolism; Sodium - chemistry; Sodium-Potassium-Exchanging ATPase - metabolism; Teleost; Temperature
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/j.cbpa.2021.110975

Na+/H+ exchangers (NHE) mediate at least part of Na+ entry into gill epithelia via Na+/NH4+ exchange. For homeostasis, Na+ entry into and exit via Na+/K+ ATPase from gill epithelia must balance. Na+/K+ ATPase activity is reduced in cold- compared to warm-acclimated freshwater temperate fish. We hypothesized gill NHE activity is greater in warm- than cold-acclimated fish when measured at acclimation temperatures, and NHE activity displays a temperature dependence similar to Na+/K+ ATPase. Since NHE mRNA expression does not differ, we measured the Na+-dependence of pH-induced Na+ fluxes in gill vesicles from warm- and cold-acclimated fathead minnows at 20o and 7 °C, and calculated maximum transport rates (Vmax) and Na+ K1/2s. We also measured NH4+-induced Na+ fluxes and Na+-induced H+ fluxes. In vesicles from warm-acclimated fish, NHE Vmaxs were 278 ± 33 and 149 ± 23 arbitrary unit/s (au/s) and Na+ K1/2s were 12 ± 4 and 6 ± 4 mmol/l when assayed at 20o and 7 °C (p