Rockefeller University Press

TABLE II

Rates of Ca²⁺ Clearance in Five Excitable Cell Types

			Rate of [Ca²⁺]_cyt fall (nM/s) @ 1000 nM Ca²⁺
Cell type	T (°C)	τ (s)	Total	SERCA	MtU	PMCA	NCX
PC12 cells (undiff.)	37	2.5	520	75	22	148	275
PC12 cells (diff.)	37	2.7	420	67	−22	214	153
Chromaffin cells	27	2–3	575	0	440	80	55
SCG neurons	33	2.2	320	110	<40	80	120
β-cells	35	1.7	500	290	0	105	105
Sperm	21–23	45–55	8	0	1.5	4.9	1.6

			Rate of [Ca²⁺]_cyt fall (nM/s) @ 1000 nM Ca²⁺
Cell type	T (°C)	τ (s)	Total	SERCA	MtU	PMCA	NCX
PC12 cells (undiff.)	37	2.5	520	75	22	148	275
PC12 cells (diff.)	37	2.7	420	67	−22	214	153
Chromaffin cells	27	2–3	575	0	440	80	55
SCG neurons	33	2.2	320	110	<40	80	120
β-cells	35	1.7	500	290	0	105	105
Sperm	21–23	45–55	8	0	1.5	4.9	1.6

Time constants of [Ca²⁺]_cyt decay τ were obtained from exponential fits of Ca²⁺ clearance time courses. The rates of [Ca²⁺]_cyt fall at 1000 nM Ca²⁺ were obtained from smoothed transport curves. Mitochondrial values from the present study are small and in the noise level. The results for mouse sperm (Wennemuth et al., 2003), rat pancreatic β cells (Chen et al., 2003), rat chromaffin cells (Herrington et al., 1996), and PC12 cells (this article) were collected in this laboratory. The results for rat superior cervical ganglion (SCG) neurons are from Wanaverbecq et al. (2003).

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