Evidence for more than one Ca/sup 2 +/ transport mechanism in mitochondria

Journal Article · Tue Aug 24 04:00:00 EDT 1976 · Biochemistry; (United States)

OSTI ID:7353092

Puskin, J S; Gunter, T E; Gunter, K K; Russell, P R

The active transport and internal binding of the Ca/sup 2 +/ analogue Mn/sup 2 +/ by rat liver mitochondria were monitored with electron paramagnetic resonance. The binding of transported Mn/sup 2 +/ depended strongly on internal pH over the range 7.7 - 8.9. Gradients of free Mn/sup 2 +/ were compared with K/sup +/ gradients measured on valinomycin-treated samples. In the steady state, the electrochemical Mn/sup 2 +/ activity was larger outside than inside the mitochondria. The observed gradients of free Mn/sup 2 +/ and of H/sup +/ could not be explained by a single ''passive'' uniport or antiport mechanism of divalent cation transport. This conclusion was further substantiated by observed changes in steady-state Ca/sup 2 +/ and Mn/sup 2 +/ distributions induced by La/sup 3 +/ and ruthenium red. Ruthenium red reduced total Ca/sup 2 +/ or Mn/sup 2 +/ uptake, and both inhibitors caused release of divalent cation from preloaded mitochondria. A model is proposed in which divalent cations are transported by at least two mechanisms: a passive uniport and an active pump, cation antiport or anion symport. The former is more sensitive to La/sup 3 +/ and ruthenium red. Under energized steady-state conditions, the net flux of Ca/sup 2 +/ or Mn/sup 2 +/ is inward over and outward over. The need for more than one transport system in regulating cytoplasmic Ca/sup 2 +/ is discussed.

• Research Organization: Univ. of Rochester, NY
• OSTI ID: 7353092
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 15:17; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ATOMIC IONS
BINDING ENERGY
BIOCHEMICAL REACTION KINETICS
CALCIUM IONS
CELL CONSTITUENTS
CHARGED PARTICLES
DIFFUSION
ELECTRON SPIN RESONANCE
ENERGY
HYDROGEN IONS
IONS
KINETICS
LANTHANUM IONS
MAGNETIC RESONANCE
MANGANESE IONS
MITOCHONDRIA
ORGANOIDS
REACTION KINETICS
RESONANCE