Amiloride and carotid body chemoreception of hypercapnia and hypoxia.
The sodium-proton (Na(+)-H+) antiporter has been found in virtually every tissue where its presence has been investigated. Its principal physiological role is to regulate intracellular pH (pHi). Amiloride (10(-3)-10(-4) M) is a known blocker of the antiporter when Na is present in normal physiological concentrations (130-140 x 10(-3) M). In order to determine if the Na(+)-H+ antiporter participated in the chemoreception of hypercapnia or hypoxia anesthetized, paralyzed, artificially ventilated cats were fitted with a loop in the right common carotid artery for the selective perfusion of the carotid body. Neural activity (imp/10 sec) was recorded from single or few fiber preparations during hypercapnia (PaCO2 = 48-64 Torr) while the carotid body was perfused with Krebs-Ringer bicarbonate solution for 2.5 min, then with its own hypercapnic arterial blood (4 min), then with Krebs-Ringer bicarbonate solution containing 0.6-0.8 x 10(-3) M amiloride (2.5 min), then with its own hypercapnic blood (4 min). After 20 min of rest the protocol was repeated during hypoxia (PaO2 = 35-45 Torr). The carotid body response to hypercapnic blood was unaffected by a preceding perfusion of the amiloride-containing solution but the response to hypoxic blood was decreased by 25% by the amiloride-containing solution. The data suggest the possibility of different mechanisms being involved in the chemoreception of hypercapnia and hypoxia.
Fitzgerald
R S
RS
Department of Physiology, School of Medicine, University of Pennsylvania, Philadelphia.
Shirahata
M
M
Lahiri
S
S
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D002344:Carotid Body / Q000187:drug effects* / Q000503:physiopathology; D002352:Carrier Proteins / Q000378:metabolism; D002415:Cats; D002628:Chemoreceptor Cells / Q000187:drug effects* / Q000503:physiopathology; D006935:Hypercapnia / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology; D066298:In Vitro Techniques; D010477:Perfusion; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers
D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D012964:Sodium