title: Functional mitochondria are required for O2 but not CO2 sensing in immortalized adrenomedullary chromaffin cells.
abstract: Catecholamine (CAT) release from adrenomedullary chromaffin cells (AMC) in response to stressors such as low O(2) (hypoxia) and elevated CO(2)/H(+) is critical during adaptation of the newborn to extrauterine life. Using a surrogate model based on a v-myc immortalized adrenal chromaffin cell line (i.e., MAH cells), combined with genetic perturbation of mitochondrial function, we tested the hypothesis that functional mitochondria are required for O(2) sensing. Wild-type MAH cells responded to both hypoxia and increased CO(2) (hypercapnia) with K(+) current inhibition and membrane depolarization. Additionally, these stimuli caused a rise in cytosolic Ca(2+) and CAT secretion, determined by fura-2 spectrofluorimetry and carbon fiber amperometry, respectively. In contrast, mitochondria-deficient (rho(0)) MAH cells were hypoxia insensitive, although responses to hypercapnia and expression of several markers, including carbonic anhydrase II, remained intact. Rotenone (1 microM), a mitochondrial complex I blocker known to mimic and occlude the effects of hypoxia in primary AMC, was effective in wild-type but not rho(0) MAH cells. These data demonstrate that functional mitochondria are involved in hypoxia-sensing by adrenal chromaffin cells. We also show for the first time that, like their neonatal chromaffin cell counterparts, MAH cells are CO(2) sensors; however, this property is independent of functional mitochondria.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Buttigieg
authors.forename: S T
authors.initials: ST
authors.lastname: Brown
authors.forename: M
authors.initials: M
authors.lastname: Lowe
authors.forename: M
authors.initials: M
authors.lastname: Zhang
authors.forename: C A
authors.initials: CA
authors.lastname: Nurse
mesh_terms: D000313:Adrenal Medulla / Q000166:cytology*; D000818:Animals; D002245:Carbon Dioxide / Q000378:metabolism*; D002395:Catecholamines / Q000378:metabolism; D015687:Cell Hypoxia; D002460:Cell Line; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D045222:Electron Transport Chain Complex Proteins / Q000037:antagonists & inhibitors; D008928:Mitochondria / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D012402:Rotenone / Q000494:pharmacology
chemical_list: D002395:Catecholamines; D045222:Electron Transport Chain Complex Proteins; D012402:Rotenone; D002245:Carbon Dioxide; D010100:Oxygen