Dropping the base: recovery from extreme hypercarbia in the CO 2 tolerant Pacific hagfish ( Eptatretus stoutii )

摘要: Hagfish are capable of tolerating extreme hypercapnia (> 30 Torr) by mounting substantial plasma [HCO3−] (hypercarbia) to compensate for CO2-mediated acidosis. The goal this study was characterize the mechanistic hypercarbia-recovery strategies in highly CO2 tolerant hagfish. We exposed hagfish (30 Torr) 48 h and allowed a 24 h recovery period normocapnic seawater. Within 8 h period, compensatory load (~ 70 mmol L−1) rapidly offloaded. While increases both whole-animal HCO3− excretion glomerular filtration were observed throughout (2–8 h), neither can fully account rates loss, which peaked at ~ 3.5 mmol kg−1 h−1. Inhibition carbonic anhydrase via acetazolamide revealed that restoration from hypercapnia-induced hypercarbia is likely facilitated dualistic manner, initially relying on mediated offloading Cl−/HCO3− exchange processes, either upregulated or further activated as progresses.