Table 1.

Agonist effects on maximum MgATPase activity and maximum active tension in wild-type and mutant myofibrils

		No treatment	10 nm ET-1	100 nm PMA	10 nm Iso
Wild-type	Maximum ATPase rate	207 ± 16	190 ± 26	175 ± 17*	286 ± 12*
	Difference	—	n.s.	−16%	+38%
	Maximum tension	14.5 ± 1.1	12.8 ± 0.9	14.6 ± 1.6	12.7 ± 1.1
	Difference	—	n.s.	n.s.	n.s.
Ala2nb	Maximum ATPase rate	197 ± 10	148 ± 15*	149 ± 15*	192 ± 18
	Difference	—	−25%	−24%	n.s.
	Maximum tension	15.1 ± 1.3	14.0 ± 1.3	15.1 ± 1.2	13.8 ± 1.2
	Difference	—	n.s.	n.s.	n.s.
Ala5nb	Maximum ATPase rate	176 ± 11	168 ± 9	165 ± 13	172 ± 17
	Difference	—	n.s.	n.s.	n.s.
	Maximum tension	12.5 ± 1.2	13.3 ± 0.8	13.0 ± 1.5	13.5 ± 1.3
	Difference	—	n.s.	n.s.	n.s.

Maximum MgATPase in units of (nmol P_i) min⁻¹ (mg protein)⁻¹ measured at pCa 4. Maximum active tension (total minus resting) in units of μm mm⁻². Resting tension values were: 1.5 ± 0.2 (all wild-type), 1.6 ± 0.3 (all Ala₂) and 1.8 ± 0.3 (all Ala₅) in mm mm⁻².

^*P < 0.05; n.s. = not significant; Data from a minimum of six separate experiments are reported as mean ±s.e.m.