Postnatal development of carotid body glomus cell response to hypoxia.
This study examines developmental changes in CB glomus cell depolarization, intracellular calcium ([Ca(2+)](i)) and the magnitude of an O(2)-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 [Ca(2+)](i) and membrane potential (E(m)) during normoxia and hypoxia. Resting E(m) in normoxia was similar at both ages. Hypoxia caused a larger E(m) depolarization and correspondingly larger [Ca(2+)](i) response in glomus cells from 11- to 14-day-old rats compared to 1-3-day-old rats. E(m) and [Ca(2+)](i) responses to 40mM 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 O(2)-sensitive background K(+) conductance. These results support the hypothesis that postnatal maturation of glomus cell O(2) sensitivity involves developmental regulation of the expression and/or O(2)-sensitivity of background ionic conductances.
Wasicko
M J
MJ
Johns Hopkins University School of Medicine, Johns Hopkins Children's Center, Baltimore, MD, United States.
Breitwieser
G E
GE
Kim
I
I
Carroll
J L
JL
D015761:4-Aminopyridine / Q000494:pharmacology; D000375:Aging; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002344:Carotid Body / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D025802:Electric Capacitance; D017097:Electric Impedance; D000860:Hypoxia / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology*; D007425:Intracellular Membranes / Q000378:metabolism; D008564:Membrane Potentials; D008566:Membranes / Q000378:metabolism / Q000503:physiopathology; D009994:Osmolar Concentration; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D012146:Rest; D019789:Tetraethylammonium / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D019789:Tetraethylammonium; D015761:4-Aminopyridine; D002118:Calcium