AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 5 801-L808, Copyright © 1995 by American Physiological Society
Developmental changes in intracellular Ca2+ response of carotid chemoreceptor cells to hypoxia
L. M. Sterni, O. S. Bamford, S. M. Tomares, M. H. Montrose and J. L. Carroll
Department of Pediatrics, Johns Hopkins Children's Center, Baltimore, Maryland, USA.
The carotid chemoreceptor response to hypoxia is weak just after birth and
increases during postnatal development. The mechanisms underlying
chemoreceptor maturation are unknown. We tested the hypothesis that carotid
chemoreceptor maturation occurs at the glomus cell level by measuring
intracellular calcium ([Ca2+]i) mobilization in response to hypoxia,
anoxia, and NaCN in freshly dissociated cells from newborn vs. adult rabbit
carotid bodies. Cells were loaded with fura 2 and superfused at 37 degrees
C with balanced salt solution equilibrated with 5% CO2. [Ca2+]i
mobilization in response to 3-min challenges of hypoxia (PO2 approximately
15 mmHg), anoxia (PO2 approximately 0 mmHg), and NaCN (1 mM) was measured
using a digital imaging microscope. The fluorescence intensity ratio was
used to calculate [Ca2+]i. Peak [Ca2+]i responses to all three challenges
were three- to fivefold greater in glomus cells from adult compared with
newborn carotid chemoreceptors. In addition, the average normoxic [Ca2+]i
baseline was approximately threefold higher in the adult glomus cells.
These results suggest that carotid chemoreceptor glomus cell sensitivity to
natural stimuli, as reflected by the [Ca2+]i response, depends on the level
of postnatal maturity.
