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1 Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, California 95616-8751; and 2 Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
Cardioventilatory variables and blood-gas,
acid-base status were measured in cannulated white sturgeon
(Acipenser transmontanus) maintained at 19°C during
normocapnic and hypercapnic (PwCO2 ~20 Torr)
water conditions and after the injection of adrenergic analogs. Hypercapnia produced significant increases in arterial
PCO2, ventilatory frequency, and plasma
concentration of cortisol and epinephrine, and it produced significant
decreases in arterial pH and plasma concentration of glucose but no
change in arterial PO2, hematocrit, and
concentration of lactate or norepinephrine. Hypercapnia
significantly increased cardiac output (Q) by 22%, mean arterial
pressure (MAP) by 8%, and heart rate (HR) by 8%. However, gut blood
flow (GBF) remained constant. In normocapnic fish, phenylephrine
significantly constricted the splanchnic circulation, whereas
isoproterenol significantly increased Q and produced a systemic
vasodilation. During hypercapnia, propranolol significantly decreased
Q, GBF, MAP, and HR, whereas phentolamine significantly decreased MAP and increased GBF. These changes suggest that cardiovascular function in the white sturgeon is sensitive to both
- and
-adrenergic modulation. We found microspheres to be unreliable in predicting GBF on
the basis of our comparisons with simultaneous direct measurements of
GBF. Overall, our results demonstrate that environmental hypercapnia (e.g., as is experienced in high-intensity culture situations) elicits
stress responses in white sturgeon that significantly elevate
steady-state cardiovascular and ventilatory activity levels.
cardiac output; gut blood flow; blood pressure; Acipenser; acid-base
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