Acid-base-electrolyte balance responses to catecholamine antagonists in Ambystoma tigrinum.
Neotenic larval Ambystoma tigrinum were subjected to hypercapnia (3% CO2, 22 Torr) for 24 h under different conditions: alpha-adrenergic blockade using phentolamine, beta-adrenergic blockade using propranolol, and sham treatments. The sham animals were able to carry out a partial extracellular pH compensation that consisted of an increase in extracellular [HCO3-]. Animals treated with catecholamine antagonists did not compensate to the same extent. Analysis of plasma samples by high-performance liquid chromatography with electrochemical detection revealed a significant increase in circulating norepinephrine, but not epinephrine, during the high-CO2 exposure. Measurements of cutaneous ion transport showed that beta-antagonists block the increased Na+ influx associated with hypercapnia, whereas alpha-antagonists inhibited the decrease in cutaneous Cl- influx that is also associated with respiratory acidosis. Additionally, both alpha- and beta-blockers inhibited the increase in transcutaneous potential difference that accompanied the respiratory acidosis. The results are consistent with a role for circulating catecholamines in compensatory ion transport responses to respiratory acidosis in this species.
Stiffler
D F
DF
Biological Sciences Department, California State Polytechnic University, Pomona 91768.
Kopecky
M E
ME
Thompson
M L
ML
Boutilier
R G
RG
D000136:Acid-Base Equilibrium; D000557:Ambystoma / Q000378:metabolism*; D000818:Animals; D002245:Carbon Dioxide / Q000494:pharmacology; D002395:Catecholamines / Q000037:antagonists & inhibitors* / Q000097:blood; D004573:Electrolytes / Q000378:metabolism*; D004594:Electrophysiology; D004781:Environmental Exposure; D005740:Gases / Q000097:blood; D006935:Hypercapnia / Q000097:blood; D007477:Ions; D007814:Larva; D010646:Phentolamine / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology*; D012016:Reference Values
D002395:Catecholamines; D004573:Electrolytes; D005740:Gases; D007477:Ions; D002245:Carbon Dioxide; D011433:Propranolol; D010646:Phentolamine