Branchial membrane-associated carbonic anhydrase activity maintains CO2 excretion in severely anemic dogfish. Gilmour, K. M. & Perry, S. F. American Journal of Physiology-Regulatory Integrative and Comparative Physiology, 286(6):R1138–R1148, June, 2004.
doi  abstract   bibtex   
Plasma CO2 reactions in Pacific spiny dogfish ( Squalus acanthias) have access to plasma and gill membrane-associated carbonic anhydrase ( CA). Acute severe experimental anemia and selective CA inhibitors were used to investigate the role of extracellular CA in CO2 excretion. Anemia was induced by blood withdrawal coupled to volume replacement with saline. Lowering hematocrit from 14.2 +/- 0.4% (mean +/- SE; N = 31) to 5.2 +/- 0.1% ( N = 31) had no significant impact on arterial or venous CO2 tensions (Pa-CO2 and Pv(CO2), respectively) over the subsequent 2 h. PCO2 was maintained despite the reduction in red cell number and a significant 32% increase in cardiac output ((V) over dot(b)), both of which have been found to cause Pa-CO2 increases in teleost fish. By contrast, treatment of anemic dogfish with the CA inhibitors benzolamide (1.3 mg/kg) or F3500 (50 mg/kg), to selectively inhibit extracellular CA, elicited rapid and significant increases in Pa-CO2 of 0.68 +/- 0.17 Torr (N = 6) and 0.53 +/- 0.11 Torr (N = 7), respectively, by 30 min after treatment. These findings provide a functional context in which extracellular CA in dogfish contributes substantially to CO2 excretion. Additionally, the apparent lack of effect of (V) over dot(b) changes on PCO2 suggests that, in contrast to teleost fish, CO2 excretion in dogfish does not behave as a diffusion-limited system.
@article{gilmour_branchial_2004,
	title = {Branchial membrane-associated carbonic anhydrase activity maintains {CO2} excretion in severely anemic dogfish},
	volume = {286},
	shorttitle = {Branchial membrane-associated carbonic anhydrase activity maintains {CO2} excretion in severely anemic dogfish},
	doi = {10.1152/ajpregu.00219.2003},
	abstract = {Plasma CO2 reactions in Pacific spiny dogfish ( Squalus acanthias) have access to plasma and gill membrane-associated carbonic anhydrase ( CA). Acute severe experimental anemia and selective CA inhibitors were used to investigate the role of extracellular CA in CO2 excretion. Anemia was induced by blood withdrawal coupled to volume replacement with saline. Lowering hematocrit from 14.2 +/- 0.4\% (mean +/- SE; N = 31) to 5.2 +/- 0.1\% ( N = 31) had no significant impact on arterial or venous CO2 tensions (Pa-CO2 and Pv(CO2), respectively) over the subsequent 2 h. PCO2 was maintained despite the reduction in red cell number and a significant 32\% increase in cardiac output ((V) over dot(b)), both of which have been found to cause Pa-CO2 increases in teleost fish. By contrast, treatment of anemic dogfish with the CA inhibitors benzolamide (1.3 mg/kg) or F3500 (50 mg/kg), to selectively inhibit extracellular CA, elicited rapid and significant increases in Pa-CO2 of 0.68 +/- 0.17 Torr (N = 6) and 0.53 +/- 0.11 Torr (N = 7), respectively, by 30 min after treatment. These findings provide a functional context in which extracellular CA in dogfish contributes substantially to CO2 excretion. Additionally, the apparent lack of effect of (V) over dot(b) changes on PCO2 suggests that, in contrast to teleost fish, CO2 excretion in dogfish does not behave as a diffusion-limited system.},
	number = {6},
	journal = {American Journal of Physiology-Regulatory Integrative and Comparative Physiology},
	author = {Gilmour, K. M. and Perry, S. F.},
	month = jun,
	year = {2004},
	keywords = {Squalus acanthias},
	pages = {R1138--R1148},
}
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