EFFECT OF IRON-DEFICIENCY ON THE RESPIRATION OF SYCAMORE (ACER-PSEUDOPLATANUS L) CELLS

The effects of iron deficiency on cell culture growth, cell respiratio n, mitochondrial oxidative properties, and the electron transport chai n were studied with suspension-cultured sycamore (Acer pseudoplatanus L.) cells. Iron deprivation considerably decreased the initial growth rates and limited the maximum density of the cells. Under these condit ions, the cells remained swollen throughout their growth. The absence of iron led to a steady decline in the uncoupled rate of O2 consumptio n. When the uncoupled rate of O2 uptake closely approximated the respi ratory rate, the cells began to collapse. At this stage, the level of all the cytochromes and electron paramagnetic resonance-detectable Fe- S clusters of the mitochondrial inner membrane were dramatically decre ased. Nevertheless, it appeared from substrate oxidation measurements that this overall depletion in iron-containing components solely distu rbed the functioning of complex II, whereas neither complexes I, III, or IV, nor the machinery involved in ATP synthesis, was apparently imp aired in iron-deficient mitochondria. However, our results suggest tha t the impairment of complex II resulted in a strong reduction of the o verall capacity of the mitochondrial electron transport chain, which w as responsible for determining the rate of endogenous respiration in s ycamore cells. Finally, this situation led to a depletion of various e nergy metabolites that could contribute to the premature cell death.