Postnatal development of carotid body glomus cell response to hypoxia

This study examines developmental changes in CB glomus cell depolarization, intracellular calcium ([Ca2+]i) and the magnitude of an O2-sensitive background ionic conductance that may play roles in the postnatal increase in oxygen sensitivity of glomus cells isolated from rats of 1–3 days and 11–14 days postnatal age. Using fura-2 and perforated patch whole cell recordings, we simultaneously measured [Ca2+]i and membrane potential (Em) during normoxia and hypoxia. Resting Em in normoxia was similar at both ages. Hypoxia caused a larger Em depolarization and correspondingly larger [Ca2+]i response in glomus cells from 11- to 14-day-old rats compared to 1–3-day-old rats. Em and [Ca2+]i responses to 40 mM K+ were identical between the two age groups. Under normoxic conditions both age groups had similar background conductances. Under anoxic conditions (at resting membrane potential) background K+ conductance decreased significantly more in cells from 11- to 14-day-old rats compared to cells from 1- to 3-day-old rats. Glomus cells from newborns therefore have less O2-sensitive background K+ conductance. These results support the hypothesis that postnatal maturation of glomus cell O2 sensitivity involves developmental regulation of the expression and/or O2-sensitivity of background ionic conductances.