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Livermore S, Piskuric NA, Buttigieg J, Zhang M, Nurse CA. Low glucose sensitivity and polymodal chemosensing in neonatal rat adrenomedullary chromaffin cells. Am J Physiol Cell Physiol 2011; 301:C1104-15. [DOI: 10.1152/ajpcell.00170.2011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucose is the primary metabolic fuel in mammalian fetuses, yet mammals are incapable of endogenous glucose production until several hours after birth. Thus, when the maternal supply of glucose ceases at birth there is a transient hypoglycemia that elicits a counterregulatory surge in circulating catecholamines. Because the innervation of adrenomedullary chromaffin cells (AMCs) is immature at birth, we hypothesized that neonatal AMCs act as direct glucosensors, a property that could complement their previously established roles as hypoxia and acid hypercapnia sensors. During perforated-patch, whole cell recordings, low glucose depolarized and/or excited a subpopulation of neonatal AMCs; in addition, aglycemia (0 mM glucose) caused inhibition of outward K+ current, blunted by the simultaneous activation of glibenclamide-sensitive KATP channels. Some cells were excited by each of the three metabolic stimuli, i.e., aglycemia, hypoxia (Po2 ∼30 mmHg), and isohydric hypercapnia (10% CO2; pH = 7.4). Using carbon fiber amperometry, aglycemia and hypoglycemia (3 mM glucose) induced robust catecholamine secretion that was sensitive to nickel (50 μM and 2 mM) and the L-type Ca2+ channel blocker nifedipine (10 μM), suggesting involvement of both T-type and L-type voltage-gated Ca2+ channels. Fura-2 measurements of intracellular Ca2+ ([Ca2+] i) revealed that ∼42% of neonatal AMCs responded to aglycemia with a significant rise in [Ca2+] i. Approximately 40% of these cells responded to hypoxia, whereas ∼25% cells responded to both aglycemia and hypoxia. These data suggest that together with hypoxia and acid hypercapnia, low glucose is another important metabolic stimulus that contributes to the vital asphyxia-induced catecholamine surge from AMCs at birth.
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Affiliation(s)
- S. Livermore
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
| | - N. A. Piskuric
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
| | - J. Buttigieg
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
- Department of Biology, University of Regina, Regina, Saskatchewan, Canada
| | - M. Zhang
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
| | - C. A. Nurse
- Department of Biology, McMaster University, Hamilton, Ontario, Canada; and
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Lu G, Wang Z, He S, Li B, Huang Z, Chen Q, Jin P, Su R. Retracted. "Changes in the Tei index during acute fetal hypoxemia in the near-term ovine fetus after intermittent umbilical cord occlusion". ULTRASOUND IN OBSTETRICS & GYNECOLOGY : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF ULTRASOUND IN OBSTETRICS AND GYNECOLOGY 2009; 34:i-viii. [PMID: 17639580 DOI: 10.1002/uog.3997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
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