Effects of hypercapnia on blood-gas and acid-base status in the white sturgeon, Acipenser transmontanus

• Published in: Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology Vol. 168; no. 1; pp. 50 - 60
• Main Authors: Crocker, C. E., Cech Jr, J. J.
• Format: Journal Article
• Language: English
• Published: 01.02.1998
• Subjects: Acipenser transmontanus; Freshwater; Marine
• ISSN: 0174-1578; 1432-136X
• DOI: 10.1007/s003600050120

The effect of environmental hypercapnia on respiratory and acid-base variables was studied in white sturgeon, Acipenser transmontanus. Blood PCO sub(2), PO sub(2), pH, hemoglobin concentration, and plasma lactate, glucose, catecholamines and cortisol were measured first under normocapnia (water PCO sub(2) < 0.5 Torr, 1 Torr = 133.32 Pa), then under hypercapnia (25-35 Torr) and a final return to normocapnia at 19 plus or minus 0.5 degree C. Acute ( less than or equal to 2h) hypercapnia significantly increased arterial PCO sub(2) (8-fold increase), ventilation frequency (2-fold increase), plasma HCO sub(3) super(-) (2.3-fold) and decreased arterial pH (to 7.15 plus or minus 0.02). After 24 h, norepinephrine, epinephrine and cortisol, were significantly increased, and arterial pH reached its nadir (7.10 plus or minus 0.03). During the 72-and 96-h-periods, arterial PCO sub(2) (24 plus or minus 4.4 Torr) and ventilatory frequency (105 plus or minus 5 breaths min super(-1)) stabilized, HCO sub(3) super(-) reached its apparent maximum (23.6 plus or minus 0.0 mmol super(-1)), glucose decreased by 32%, and pH increased significantly to 7.31 + 0.03. The return to normocapnia completely restored arterial PCO sub(2) (2.5 plus or minus 0.14 Torr), HCO sub(3) super(-) (7.4 plus or minus 0.59 mmol times l super(-1)), ventilation frequency (71 plus or minus 7 breaths times min super(-1)), and pH (7.75 plus or minus 0.04). Overall, hypercapnia produced a respiratory acidosis, hyperventilation, a transient norepinephrine "spike", and increased plasma catecholamines, cortisol, and arterial PO sub(2). The respiratory acidosis was only partially compensated (35% pH restoration) 96 h after the onset of hypercapnia and resulted in a significantly decreased blood-O sub(2) affinity (Bohr effect), as determined by construction of in vitro blood O sub(2) equilibrium curves at 15 degree C and 20 degree C. Prolonged exposure to hypercapnia may lead to acid-base disturbances and negatively affect growth of white sturgeon.