Cat carotid body: oxygen consumption and other parameters

Cats were anesthetized with pentobarbital, pump ventilated with air, and given heparin, and the carotid body (CB) was vascularly isolated except for the supplying artery. The CB could be normally blood perfused, or alternatively, perfused with Locke's solution; flow of either could be stopped suddenly. Sinus nerve discharge was measured. Tissue oxygen tension (TPO2) in the CB was measured with an O2 microelectrode. Oxygen consumption rates (VO2) calculated from the disappearance curve of O2 during stopped flow were PO2 dependent. When TPO2 was high (100-130 Torr), VO2 (ml.100 g-1.min-1) averaged 1.9 +/- 0.18 (SE) during blood perfusion and either 1.9 +/- 0.1 during perfusion with Locke's solution equilibrated with 25% O2-5% CO2-70% N2 or 1.4 +/- 0.08 when the Locke's solution was equilibrated with air. This significant effect of CO2 could have been due to the delayed onset of sinus nerve discharge when CO2 was not added to the perfusion solution. The number of red blood cells in histological sections from CB frozen during stopped flow of blood was significantly below normal. We concluded that the similarity of the disappearance curves during stopped flow of blood and Locke's solutions was primarily due to the extrusion of red blood cells. In five experiments the broken-off tip of the O2 microelectrode was found in the core of the CB.