In the liver cell, the fastest system involved with regulation of cytoplasmic Ca2+ is the mitochondrial Ca2+ transport system. Several mechanisms have been found to be involved with mitochondrial Ca2+ transport. One of them, the Na+-independent Ca2+ efflux mechanism has neither been convincingly identified nor well characterized in published work. This mechanism is felt to play a crucial, central role in regulation of cytosolic Ca2+. Several possible hypotheses as to the nature of the Na+ independent Ca2+ efflux mechanism have been eliminated by earlier work. We show within this application preliminary data, which strongly supports the proposition that the Na+-independent Ca2+ efflux mechanism is active. This new data also supports the view that the properties of the Na+-independent Ca2+ efflux mechanism have geen disguised in much past work by induction of a membrane permeability transformation to a state of higher permeability by the conditions of some efflux experiments. We propose to systematically test those agents reported to protect against the permeability transformation in an effort to find conditions in which Ca2+ efflux under de-energized conditions can be studied without induction of the transformation. We further propose: (1) to study the inhibition of Ca2+ efflux by metabolic inhibitors. (2) to study the response of the efflux mechanism under both energized and de-energized conditions to changes in the Ca2+ chemical potential. (3) to study competition for efflux between Mn2+, Sr2+, and Ca2+. (4) to study Ca2+:Ca2+, Mn2+:Ca2+, and Sr2+:Ca2+ exchange under both energized and de-energized conditions. (5) to study the energization properties of mitochondria as they pass through the permeability transformation with a new cell sorter technique. In addition, we propose to determine if the Na+-dependent Ca2+ efflux mechanism sometimes seen in liver mitochondria is like that of heart mitochondria.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM035550-05
Application #
3288495
Study Section
Physical Biochemistry Study Section (PB)
Project Start
1985-08-30
Project End
1991-07-31
Budget Start
1989-08-01
Budget End
1991-07-31
Support Year
5
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Rochester
Department
Type
School of Medicine & Dentistry
DUNS #
208469486
City
Rochester
State
NY
Country
United States
Zip Code
14627
Gavin, C E; Gunter, K K; Gunter, T E (1999) Manganese and calcium transport in mitochondria: implications for manganese toxicity. Neurotoxicology 20:445-53
Sparagna, G C; Gunter, K K; Sheu, S S et al. (1995) Mitochondrial calcium uptake from physiological-type pulses of calcium. A description of the rapid uptake mode. J Biol Chem 270:27510-5
Gunter, T E; Gunter, K K; Sheu, S S et al. (1994) Mitochondrial calcium transport: physiological and pathological relevance. Am J Physiol 267:C313-39
Baysal, K; Jung, D W; Gunter, K K et al. (1994) Na(+)-dependent Ca2+ efflux mechanism of heart mitochondria is not a passive Ca2+/2Na+ exchanger. Am J Physiol 266:C800-8
Sparagna, G C; Gunter, K K; Gunter, T E (1994) A system for producing and monitoring in vitro calcium pulses similar to those observed in vivo. Anal Biochem 219:96-103
Gunter, T E (1994) Cation transport by mitochondria. J Bioenerg Biomembr 26:465-9
Gunter, K K; Gunter, T E (1994) Transport of calcium by mitochondria. J Bioenerg Biomembr 26:471-85
Sheu, S S; Jou, M J (1994) Mitochondrial free Ca2+ concentration in living cells. J Bioenerg Biomembr 26:487-93
Gavin, C E; Gunter, K K; Gunter, T E (1992) Mn2+ sequestration by mitochondria and inhibition of oxidative phosphorylation. Toxicol Appl Pharmacol 115:1-5
Gavin, C E; Gunter, K K; Gunter, T E (1991) Mn2+ transport across biological membranes may be monitored spectroscopically using the Ca2+ indicator dye antipyrylazo III. Anal Biochem 192:44-8

Showing the most recent 10 out of 19 publications