TY - JOUR
T1 - Renal responses of trout to chronic respiratory and metabolic acidoses and metabolic alkalosis
AU - Wood, Chris M.
AU - Milligan, C. Louise
AU - Walsh, Patrick J.
PY - 1999/8
Y1 - 1999/8
N2 - Exposure to hyperoxia (500-600 torr) or low pH (4.5) for 72 h or NaHCO3 infusion for 48 h were used to create chronic respiratory (RA) or metabolic acidosis (MA) or metabolic alkalosis in freshwater rainbow trout. During alkalosis, urine pH increased, and [titratable acidity (TA) - HCO3/-] and net H+ excretion became negative (net base excretion) with unchanged NH4/+ efflux. During RA, urine pH did not change, but net H+ excretion increased as a result of a modest rise in NH4/+ and substantial elevation in [TA - HCO3/-] efflux accompanied by a large increase in inorganic phosphate excretion. However, during MA, urine pH fell, and net H+ excretion was 3.3- fold greater than during RA, reflecting a similar increase in [TA - HCO3/-] and a smaller elevation in phosphate but a sevenfold greater increase in NH4/+ efflux. In urine samples of the same pH, [TA - HCO3/-] was greater during RA (reflecting phosphate secretion), and [NH4/+] was greater during MA (reflecting renal ammoniagenesis). Renal activities of potential ammoniagenic enzymes (phosphate-dependent glutaminase, glutamate dehydrogenase, α-ketoglutarate dehydrogenase, alanine aminotransferase, phosphoenolpyruvate carboxykinase) and plasma levels of cortisol, phosphate, ammonia, and most amino acids (including glutamine and alanine) increased during MA but not during RA, when only alanine aminotransferase increased. The differential responses to RA vs. MA parallel those in mammals; in fish they may be keyed to activation of phosphate secretion by RA and cortisol mobilization by MA.
AB - Exposure to hyperoxia (500-600 torr) or low pH (4.5) for 72 h or NaHCO3 infusion for 48 h were used to create chronic respiratory (RA) or metabolic acidosis (MA) or metabolic alkalosis in freshwater rainbow trout. During alkalosis, urine pH increased, and [titratable acidity (TA) - HCO3/-] and net H+ excretion became negative (net base excretion) with unchanged NH4/+ efflux. During RA, urine pH did not change, but net H+ excretion increased as a result of a modest rise in NH4/+ and substantial elevation in [TA - HCO3/-] efflux accompanied by a large increase in inorganic phosphate excretion. However, during MA, urine pH fell, and net H+ excretion was 3.3- fold greater than during RA, reflecting a similar increase in [TA - HCO3/-] and a smaller elevation in phosphate but a sevenfold greater increase in NH4/+ efflux. In urine samples of the same pH, [TA - HCO3/-] was greater during RA (reflecting phosphate secretion), and [NH4/+] was greater during MA (reflecting renal ammoniagenesis). Renal activities of potential ammoniagenic enzymes (phosphate-dependent glutaminase, glutamate dehydrogenase, α-ketoglutarate dehydrogenase, alanine aminotransferase, phosphoenolpyruvate carboxykinase) and plasma levels of cortisol, phosphate, ammonia, and most amino acids (including glutamine and alanine) increased during MA but not during RA, when only alanine aminotransferase increased. The differential responses to RA vs. MA parallel those in mammals; in fish they may be keyed to activation of phosphate secretion by RA and cortisol mobilization by MA.
KW - Cortisol
KW - Glutamine
KW - Phosphate
KW - Renal ammoniagenesis
KW - Titratable acidity
UR - http://www.scopus.com/inward/record.url?scp=0032884919&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0032884919&partnerID=8YFLogxK
U2 - 10.1152/ajpregu.1999.277.2.r482
DO - 10.1152/ajpregu.1999.277.2.r482
M3 - Article
C2 - 10444555
AN - SCOPUS:0032884919
VL - 277
SP - R482-R492
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
SN - 0363-6143
IS - 2 46-2
ER -