Gene expression of TREK K+ channels in rat carotid body (CB)

Abstract

Oxygen sensing by CB glomus cells shows postnatal development in mammals. Both hypoxia-induced depolarization and [Ca2+]i response are small at birth and increase with age, but mechanisms are poorly understood. We hypothesized that expression of TREK-1, a two-pore domain K+ channel, may regulate glomus cell excitability during development. Therefore, we tested whether a) TREK-1 is expressed in rat CB; b) TREK-1 expression changes with age; and c) chronic hypoxia (CH) from birth alters TREK-1 expression. rTREK-1 and rTREK-2 primers were tested on rat CB of normoxic 0–1day old (N1), 14–16 days old (N14), and 2 weeks of CH after birth with quantitative real time RT-PCR (qRT-PCR) by using SYBR green. 18s rRNA gene was used as the reference gene and relative gene expression ratio was calculated (Pfaffl MW 2001). Results Immunoreactivity for hTREK-1 was found only in glomus cells at both ages. Between P0 and P14, rTREK-1 expression declined, while rTREK-2 expression did not. TREK-1 and TREK-2 relative gene expression ratio for N1 vs. N14 CB were 0.16 ± 0.03 (n=6) (p<0.001, downregulation) and 0.93 ± 0.22 (n=4) (NS), respectively. In sharp contrast, in rats reared in 0.12 FiO2 from P0 to P14, TREK-1 expression showed almost 2 fold upregulation. The sequence of qRT-PCR amplicon of rat CB TREK-1 showed 100% homology with that of rat cerebellum TREK-1. We conclude that a) TREK-1 and TREK-2 are expressed in CB glomus cells; b) TREK-1 expression decreases >80% between P0 and P14; and c) expression of TREK-1 after birth appears to be regulated by oxygen tension. Developmental changes in TREK-1 potassium channel expression may play a role in CB functional maturation. (funded by NIH R01 HL54621 and UAMS Dean's Research Development Fund).