Table 2.

Respiratory properties of mitochondrial fractions prepared from astrocytes after mitochondrial glutathione depletion and exposure to SIN-1

	Oxygen uptake rate (ng-atom 0·min−1·mg of protein−1)
Conditions	State 3 respiration	State 4 respiration	Uncoupled respiration	ADP/0
Respiratory substrate: pyruvate plus malate
Untreated cells	25.1 ± 4.1	8.9 ± 3.0	25.8 ± 2.0	2.4 ± 0.6
Ethacrynic acid	54.0 ± 5.9**	19.0 ± 7.3*	59.1 ± 6.0**	2.0 ± 0.5
Ethacrynic acid plus SIN-1	15.8 ± 0.5*		17.9 ± 6.4
Respiratory substrate: succinate
Untreated cells	43.6 ± 8.9	14.2 ± 3.7	48.5 ± 9.1	1.3 ± 0.3
Ethacrynic acid	42.1 ± 3.3	20.5 ± 6.7	47.3 ± 3.4	1.5 ± 0.2
Ethacrynic acid plus SIN-1	24.2 ± 2.0*		24.3 ± 5.7**

Mitochondrial fractions were isolated from astrocytes after 24 hrs in HBSS. Treated cells were exposed to ethacrynic acid to deplete mitochondrial glutathione, and some preparations were further treated for 3 hr with 200 μm SIN-1. Respiratory properties were measured using an oxygen-sensitive electrode. State 3 respiration rate was determined in the presence of ADP plus respiratory substrates. State 4 respiration was measured following depletion of the ADP, and the uncoupled rate was determined after the addition of CCCP. Samples from cells treated with ethacrynic acid plus SIN-1 were poorly coupled, and state 4 values could not be reliably determined. Values are shown as mean ± SD (n = 3-5). Values significantly different from those for mitochondrial fractions from the untreated cells are indicated as follows: ^*p < 0.05, ^**p < 0.01 (one-way ANOVA with Student-Newman-Keuls test). All of the values for mitochondria from cells treated with ethacrynic were also significantly different from those for cells exposed to ethacrynic acid plus SIN-1 (p < 0.01).