QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

Help viewing high resolution images Return to article

Fig. 3. Myofibrillar ATPase activity in transgenic cardiac-muscle preparations. Myofibrils from ventricular and papillary muscles from transgenic mice were examined for myofibrillar ATPase activity in a solution (see Materials and Methods) and increasing concentrations of Ca²⁺ (pCa 9 to pCa 4.5). After a 5-minute incubation period at 30°C, the reaction was initiated with 2.5 mM ATP and terminated after 10 minutes with 5% trichloroacetic acid. Released inorganic phosphate was measured according to Fiske and Subbarow (Fiske and Subbarow, 1925). (A) ATPase-pCa relationship for Non-Tg, Tg-WT, Tg-E22K L2 and Tg-E22K L4 mouse muscle myofibrils. Statistically significant differences in the pCa₅₀ values of the Ca²⁺ sensitivity of myofibrillar ATPase activity were observed between Non-Tg (n=10) or Tg-WT (n=7) and two lines of the mutant mice, Tg-E22K, line 2 (L2) (n=8) and line 4 (L4) (n=7) (P0.01). A difference of the pCa₅₀=0.14 was observed between Tg-WT and Tg-E22K L4 myofibrils (P=0.01). Respective n_H values of the ATPase-pCa relationships were: 1.54±0.17, 1.67±0.20, 1.38±0.14 and 1.45±0.11 for Non-Tg, Tg-WT, Tg-E22K L2 and Tg-E22K L4 myofibrils. (B) The pCa₅₀ values for the ATPase-pCa dependences of Non-Tg, Tg-WT, Tg-E22K L2 and Tg-E22K L4 mouse muscle myofibrils. The Ca²⁺ sensitivity in Tg-E22K L2 (pCa₅₀=6.40±0.03, n=8) and L4 (pCa₅₀=6.41±0.03, n=7) myofibrils was increased compared with Non-Tg (pCa₅₀=6.23±0.03, n=10) or Tg-WT (pCa₅₀=6.27±0.04, n=7) myofibrils. As indicated, the differences were statistically significant (P0.01). Data are expressed as the average of n experiments ± s.e.m.

Return to article