title: Actions and interactions of norepinephrine and acetylcholine on sinus node potassium movements.
abstract: The influence of norepinephrine and/or acetylcholine on K uptake of the guinea pig sinus node was investigated. Both "high" (10(-6) M) and "low" (10(-9) M) mediator concentrations were employed. The following results were obtained: 1) high concentration of norepinephrine increased K uptake; 2) high concentration of acetylcholine had a similar effect; 3) simultaneous exposure to both mediators did not lead to summation of the effects; 4) low concentration of norepinephrine depressed K uptake; 5) high concentration of acetylcholine overcame the inhibitory effect of the small concentration of norepinephrine; 6) 2-deoxy-D-glucose did not abolish the stimulating effect of acetylcholine on potassium uptake; and 7) strophanthidin abolished the stimulatory effect of norepinephrine, but not that of acetylcholine. The following conclusions are drawn: 1) both neuromediators in suitable concentrations increase K uptake in the sinus node; 2) the mechanism of such an increase is different, norepinephrine increasing the active and acetylcholine increasing the passive potassium transport; 3) a low concentration of norepinephrine depresses K uptake; and 4) when the two mediators are administered together, acetylcholine suppresses the action of norepinephrine on K transport.
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D005260:Female; D006168:Guinea Pigs; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism*; D012849:Sinoatrial Node / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000109:Acetylcholine; D011188:Potassium; D009638:Norepinephrine