Mitochondrial Content of Carotid Body Type I Cells Decreases During the Maturation of the Hypoxic Response

Abstract

Carotid body (CB) responses to hypoxia are low at birth and increase over time to mature responses. Using an in vitro rat CB‐carotid sinus nerve (CSN) preparation, Kholwadwala and Donnelly (1992) demonstrated that the CSN activity in response to hypoxia increased from low levels to a robust adult response after two weeks. This time course of maturation was paralleled by an increase in TASK channel sensitivity to hypoxia (Kim et al, 2011). The mechanism(s) which underpin this increase in O2‐sensitivity has not been addressed. However, a body of evidence suggest mitochondria in Type I cells are critical for O2‐sensing by the CB. We tested the hypothesis that changes occur in mitochondrial organization during development of O2‐sensitivity in CBs.Type I cells were isolated from juvenile (4–6 days) and mature rats (14–16 days). Cells were stained with Mitotracker and Celltracker. Total mitochondrial volume in juvenile Type I cells was 100.3 ± 13.6 μm3 (n = 23) and this was significantly smaller in mature cells, 22.6 ± 3.4 μm3 (n = 17, P<0.00003). This decrease in mitochondrial volume was not observed in non‐oxygen sensing cells (superior cervical ganglion cells).These data demonstrate significant reductions in the mitochondrial content of mature Type I cells. This will likely impact the metabolic setting of the cell and may underpin the development of O2‐sensitivity.Supported in part by an NIH grant 1RO1HL091836