Glomus cell plasma membrane vs. mitochondrial membrane potentials in
response to low Po2 and high Pco
Research field:Respiration physiology
Authors:Lahiri S, Roy A, Rozanov C, Daudu P, Al-Mehdi A B, Mokashi A.
Address of presenting
author:		Department of Physiology, University of
Pennsylvania Medical Center, Philadelphia,
PA. 19104-6085, USA.
E-mail:lahiri@mail.med.upenn.edu
Phone:(215)898-9125
Fax:(215)573-5851
Text of abstract Introduction
Low Po2 and high Pco stimulate the sensory discharge of the carotid body (CB)by raising [Ca2+]i which could be induced by depolarization of the plasma membrane and /or intracellular organelle membrane. We hypothesized that mitochondrial membrane depolarization may be responsible for the [Ca2+]i rise.

Methods
Cultured glomus cells from adult rats were used to measure plasma membrane and mitochondrial membrane potentials by using a non-invasive technique of fluorescence micro-imaging. We used two voltage sensitive dyes namely, bis-oxonol and JC-1, respectively for measuring plasma membrane and mitochondrial membrane potentials in response to moderate (Po2 ~ 50 Torr)and severe (Po2 ~ 10 Torr) hypoxia and high Pco( ~ 550 Torr).

Results
1. Moderate and severe hypoxia showed hyperpolarization of the glomus cell plasma membrane while mitochondria showed depolarization.

2. Exposure to high Pco of 550 Torr at Po2 ~ 100 Torr always depolarized mitochondrial membrane without concomittant depolarization of the plasma membrane.

Conclusions
Both hypoxia and high Pco preferentially depolarized mitochondria, suggesting that intracellular Ca2+ store participated in [Ca2+]i rise.

References
1. Lahiri, S. et al. 1993. Respir Physiol 94, 227-240
2. Al-Mehdi, A B. et al. 1996. J Cellular Physiol 166, 274-280
3. Lahiri, S. 2000. J Appl Physiol 88, 1467-1478

Keywords:Glomus cell, plasma membrane potential, mitochondrial membrane potential, fluorescence micro-imaging.

Created 2000-04-28