Table 1.

Basal respiration rates (%) of PC12 cells after different time of incubation with increasing concentration of Hg²⁺, Cd²⁺, or Cu²⁺.

Time (h)	Control	[Hg2+], μM		[Cd2+], μM				[Cu2+], μM
		10	50	10	50	100	500	10	50	100	500
3	45 ± 4	26 ± 5*	3 ± 3*	41 ± 7	25 ± 3*	16 ± 4*	2 ± 2*	43 ± 7	35 ± 7	35 ± 5	35 ± 5
5	35 ± 6					6 ± 3*
24	39 ± 7	30 ± 2	2 ± 2*	32 ± 2	13 ± 6*	7 ± 1*	0	33 ± 5	32 ± 2	34 ± 5	22 ± 8*
48	41 ± 5	74 ± 26*									15 ± 3*

Rate of oxygen uptake is presented in percentage of the maximal (fully uncoupled) respiration of the control cells. Mean ± SE; n = 3 independent experiments; *P < 0.05 compared to untreated control.