TY - JOUR
T1 - Physiological adaptations of rainbow trout to chronically elevated water pH (pH = 9.5)
AU - Wilkie, Michael P.
AU - Simmons, Heather E.
AU - Wood, Chris M.
PY - 1996/1/1
Y1 - 1996/1/1
N2 - Recent investigations have demonstrated that rainbow trout cope with acute high pH (pH > 9.0) exposure (lasting 3-8 days) through their ability to counteract high-pH-induced disturbances to ammonia excretion (JAmm), acid-base homeostasis, and electrolyte balance. In the present investigation our goal was to establish how these physiological processes were modulated during chronic (28-day) high pH (pH = 9.5) exposure. Chronic high pH led to minimal mortality, and there were no long-term changes in stress indicators levels, such as cortisol or glucose. JAmm was initially reduced by 40% at high pH but rapidly recovered and fluctuated around control rates, thereafter. Decreased JAmm was associated with an initial 2.5-fold increase in plasma ammonia concentrations (TAmm), followed by a return toward pre-exposure levels after 3 days. Overall, plasma TAmm was slightly higher (40-80%) in the treatment fish, and this likely led to plasma PNH3S that were sufficient to sustain JAmm at high pH. White muscle TAmm stores were also chronically elevated, by 50-100%. There was a transient, twofold elevation of JUrea immediately following high-pH exposure, but by 3 days JUrea had returned to control rates and stabilized thereafter. Plasma ion balance was well maintained at high pH, despite a chronic depression of Na+ influx. Even though there was a persistent respiratory alkalosis at alkaline pH, blood pH was effectively regulated by a simultaneous metabolic acid load, which was not associated with increased lactic acid production. White muscle intracellular pH (pH1) was unaltered during high pH exposure. We conclude that the long-term survival of rainbow trout in alkaline environments is facilitated by higher steady-state internal ammonia concentrations, the development of a sustained, compensatory metabolic acidosis which offsets decreased plasma PCO2, and the effective regulation of plasma electrolyte balance.
AB - Recent investigations have demonstrated that rainbow trout cope with acute high pH (pH > 9.0) exposure (lasting 3-8 days) through their ability to counteract high-pH-induced disturbances to ammonia excretion (JAmm), acid-base homeostasis, and electrolyte balance. In the present investigation our goal was to establish how these physiological processes were modulated during chronic (28-day) high pH (pH = 9.5) exposure. Chronic high pH led to minimal mortality, and there were no long-term changes in stress indicators levels, such as cortisol or glucose. JAmm was initially reduced by 40% at high pH but rapidly recovered and fluctuated around control rates, thereafter. Decreased JAmm was associated with an initial 2.5-fold increase in plasma ammonia concentrations (TAmm), followed by a return toward pre-exposure levels after 3 days. Overall, plasma TAmm was slightly higher (40-80%) in the treatment fish, and this likely led to plasma PNH3S that were sufficient to sustain JAmm at high pH. White muscle TAmm stores were also chronically elevated, by 50-100%. There was a transient, twofold elevation of JUrea immediately following high-pH exposure, but by 3 days JUrea had returned to control rates and stabilized thereafter. Plasma ion balance was well maintained at high pH, despite a chronic depression of Na+ influx. Even though there was a persistent respiratory alkalosis at alkaline pH, blood pH was effectively regulated by a simultaneous metabolic acid load, which was not associated with increased lactic acid production. White muscle intracellular pH (pH1) was unaltered during high pH exposure. We conclude that the long-term survival of rainbow trout in alkaline environments is facilitated by higher steady-state internal ammonia concentrations, the development of a sustained, compensatory metabolic acidosis which offsets decreased plasma PCO2, and the effective regulation of plasma electrolyte balance.
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U2 - 10.1002/(SICI)1097-010X(19960101)274:1<1::AID-JEZ1>3.0.CO;2-T
DO - 10.1002/(SICI)1097-010X(19960101)274:1<1::AID-JEZ1>3.0.CO;2-T
M3 - Article
AN - SCOPUS:0030021629
VL - 274
SP - 1
EP - 14
JO - Journal of Experimental Zoology Part A: Comparative Experimental Biology
JF - Journal of Experimental Zoology Part A: Comparative Experimental Biology
SN - 0022-104X
IS - 1
ER -