Age-dependence of the lateral diffusion coefficient of Con-A receptor protein in the skeletal muscle membrane of C57BL/6J mice

Abstract The lateral diffusion coefficient ( D p ) of the Con-A receptor protein was measured in the sarcolemma of the quadriceps femoris (QF) muscle of male and female C57BL/6JNia mice in four age groups between 2 and 26 months. Freshly prepared, ex vivo taken muscle strips were stained with Con-A–FL conjugate for 10 min, and fluorescence recovery after photobleaching (FRAP) measurements were carried out on 20–30 cells per animal, at 37°C. Using this technique, D p , and the fractional recovery (mobile fraction=FR%) of these proteins can be measured. In the youngest male and female age groups, D p values of 5.72E-10 and 5.43E-10 cm 2 /s, and FR% values of 43.3 and 36.3%, were found, respectively. D p displayed a characteristic, significant, negative, linear correlation with age in both sexes. The slope of the linear regression line calculated per month of age was 1.06E-11 and 0.96E-11 cm 2 /s for males and females, respectively; both of them differ from zero highly significantly. FR% values tended to increase slightly with age, yet the estimated average D p = D (FR), calculated for the total Con-A receptor pool, maintained its significant, negative, linear age-correlation. The physiological significance of these changes needs to be clarified in the future.