Table 2.

High-energy phosphate metabolism in EDL muscle

	Basal		Stimulated
	WT	CK−/−	WT	CK−/−
Phosphocreatine	66.3 ± 1.4	44.6 ± 0.9***	24.4 ± 3.9	45.7 ± 2.3***
Creatine	17.7 ± 1.4	39.3 ± 1.0***	59.6 ± 3.9	38.4 ± 2.3***
Pi	11.4 ± 0.7	25.3 ± 2.2***	54.2 ± 4.5	33.9 ± 2.3***
ATP	22.6 ± 0.5	16.7 ± 0.3***	15.3 ± 1.4	14.0 ± 1.4
ADP	2.8 ± 0.1	3.6 ± 0.2**	3.1 ± 0.1	4.0 ± 0.3*
AMP	0.09 ± 0.01	0.16 ± 0.01**	0.11 ± 0.02	0.16 ± 0.03
IMP	0.37 ± 0.10	0.28 ± 0.06	8.2 ± 1.2	2.5 ± 0.6**
Inosine	0.09 ± 0.05	0.50 ± 0.18**	0.15 ± 0.10	0.77 ± 0.25*
ATP turnover	—	—	4.8	1.7
Force–time integral	—	—	483 ± 67	201 ± 48**
Mechanical efficiency	—	—	101	118

Values are means (± s.e.m., when given) for 4–10 muscles and are given in micromoles per gram of dry muscle for metabolites. Isolated EDL muscles were incubated in oxygenated Tyrode (basal) or stimulated in oxygenated Tyrode containing 3 mm NaCN for 20s and immediately frozen in liquid nitrogen. ATP turnover during the 20s is calculated from mean values as follows: (−2ΔATP –ΔADP –Δphosphocreatine + 1.5 Δlactate)/20s and given in micromoles per second per gram of dry muscle. The force–time integral is given in (N × s)/(g dry muscle). Mechanical efficiency is calculated as mean force–time integral divided by ATP turnover and is expressed as (N × s²)/μmol.

^*P < 0.05

^**P < 0.01

^***P < 0.001 vs. WT.