Developmental loss of hypoxic chemosensitivity in rat adrenomedullary chromaffin cells.
1. We investigated whether adrenomedullary chromaffin cells (AMCs) derived from neonatal (postnatal day (P) 1-P2) and juvenile (P13-P20) rats, and maintained in short-term culture (1-3 days), express O2-chemoreceptive properties. 2. In whole-cell recordings, the majority (approximately 70%; n = 47) of neonatal AMCs were sensitive to hypoxia. Under voltage clamp, acute hypoxia (PO2 approximately 40 mmHg) suppressed voltage-dependent K+ current by 25.1 +/- 3.4% (mean +/- S.E.M.; n = 22); under current clamp, acute hypoxia caused a membrane depolarization of 14.1 +/- 1.3 mV (n = 13) from a resting potential of -54.8 +/- 2.8 mV (n = 13), and this was often sufficient to trigger action potentials. 3. Exposure of neonatal AMC cultures to a moderate (PO2 approximately 75 mmHg) or severe (PO2 approximately 35 mmHg) hypoxia for 1 h caused a dose-dependent stimulation (approximately 3 or 6 times normoxia, respectively) of catecholamine (CA) release, mainly adrenaline, determined by HPLC. This induced CA release was abolished by the L-type calcium channel blocker, nifedipine (10 microM). 4. In contrast to the above results in neonates, hypoxia had no significant effects on voltage-dependent K+ current, membrane potential, or CA release in juvenile AMCs. 5. We conclude that rat adrenal chromaffin cells possess a developmentally regulated O2-sensing mechanism, similar to carotid body type I cells.
Thompson
R J
RJ
Department of Biology, McMaster University, Hamilton, Ontario, Canada.
Jackson
A
A
Nurse
C A
CA
D000313:Adrenal Medulla / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D000375:Aging / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D002344:Carotid Body / Q000378:metabolism; D002395:Catecholamines / Q000378:metabolism; D002478:Cells, Cultured; D002628:Chemoreceptor Cells / Q000502:physiology*; D019439:Chromaffin Cells / Q000378:metabolism / Q000502:physiology*; D002851:Chromatography, High Pressure Liquid; D004594:Electrophysiology; D005260:Female; D019085:Fluorescent Antibody Technique, Direct; D000860:Hypoxia / Q000378:metabolism / Q000503:physiopathology*; D008564:Membrane Potentials / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar
D002395:Catecholamines