A sup 31 P NMR study of mitochondrial inorganic phosphate visibility: Effects of Ca sup 2+ , Mn sup 2+ , and the pH gradient

Journal Article · Tue Feb 11 00:00:00 EST 1992 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00120a007· OSTI ID:5559733

Hutson, S M; Williams, G D; Berkich, D A; LaNoue, K F; Briggs, R W ^[1]

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1. Pennsylvania State Univ., Hershey (United States)

The effects of external pH, temperature, and Ca{sup 2+} and Mn{sup 2+} concentrations on the compartmentation and NMR visibility of inorganic phosphate (P{sub i}) were studied in isolated rat liver mitochondria respiring on succinate and glutamate. Mitochondrial matrix P{sub i} is totally visible by NMR at 8C and at low external concentrations of P{sub i}. However, when the external P{sub i} concentration is increased above 7 mM, the pH gradient decreases, the amount of matrix P{sub i} increases, and the fraction not observed by NMR increases. Raising the temperature to 25C also decreases the pH gradient and the P{sub i} fraction observed by NMR. At physiologically relevant concentrations, Ca{sup 2+} and Mn{sup 2+} do not seem to play a major role in matrix P{sub i} NMR invisibility. For Ca{sup 2+} concentrations above 30 nmol/mg of protein, formation of insoluble complexes will cause loss of P{sub i} signal intensity. For Mn{sup 2+} concentrations above 2 nmol/mg of protein, the P{sub i} peak can be broadened sufficiently to preclude detection of a high-resolution signal. The results indicate that mitochondrial matrix P{sub i} should be mostly observable up to 25C by high-resolution NMR. While the exact nature of the NMR-invisible phosphate in perfused or in vivo liver is yet to be determined, better success at detecting and resolving both P{sub i} pools by NMR is indicated at high field, low temperature, and optimized pulsing conditions.

• OSTI ID: 5559733
• Journal Information: Biochemistry; (United States), Vol. 31:5; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
PHOSPHATES
NUCLEAR MAGNETIC RESONANCE
MANGANESE COMPOUNDS
MITOCHONDRIA
PH VALUE
PHOSPHORUS 31
TEMPERATURE DEPENDENCE
CELL CONSTITUENTS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
ODD-EVEN NUCLEI
OXYGEN COMPOUNDS
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
RESONANCE
STABLE ISOTOPES
TRANSITION ELEMENT COMPOUNDS
550201* - Biochemistry- Tracer Techniques