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Developmental changes in isolated rat type I carotid body cell K + currents and their modulation by hypoxia
Author(s) -
Hatton C. J.,
Carpenter E.,
Pepper D. R.,
Kumar P.,
Peers C.
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1997.049bo.x
Subject(s) - carotid body , hypoxia (environmental) , endocrinology , medicine , patch clamp , chemistry , age groups , electrophysiology , biology , oxygen , organic chemistry , demography , sociology
1 Whole‐cell patch‐clamp recordings were used to investigate possible age‐related changes in K + currents of type I carotid body cells isolated from the rat. K + current density increased with age, as measured in cells isolated from 4‐day‐old, 10‐day‐old and adult rats (≥ 5 weeks old). 2 The proportion of current reversibly inhibited by high [Mg 2+ ] (6 m m ), low [Ca 2+ ] (0.1 m m ) solutions, indicative of the proportion of current attributable to activation of Ca 2+ ‐sensitive K + (K Ca ) channels, was significantly smaller in cells of 4‐day‐old rats compared with 10‐dayold rats, despite inward Ca 2+ current densities being similar in these two age groups. Inhibition of K + currents by high [Mg 2+ ], low [Ca 2+ ] solutions was similar in 10‐day‐old and adult type I cells. 3 Hypoxia ( P O 2 , 16–23 mmHg) caused reversible reductions in type I cells from rats of all age groups. However, reductions seen in cells of 4‐day‐old rats were significantly smaller than those seen in cells of 10‐day‐olds and adults. The degree of hypoxic inhibition in these latter two groups was not significantly different. 4 In the presence of high [Mg 2+ ], low [Ca 2+ ] solutions, hypoxia ( P O 2 , 16–23 mmHg) was without significant effect on residual K + currents in cells from all age groups. 5 These observations indicate that K + current density increases with postnatal age in the rat. Between days 4 and 10, there appears to be a predominant enhancement of K Ca channels, and over the same age range hypoxic sensitivity of K + currents increases. Our findings demonstrate that this latter observation arises because hypoxia selectively inhibits K Ca channels in cells at all ages studied. These results suggest an important role for K Ca channels in postnatal maturation of hypoxic chemoreception in the rat carotid body.