GOMES, FR; REZENDE, EL; BUNKERS, JL; RIVAS, DA; YASPELKIS, III, BB; GARLAND, JR, T; Univ. of Cal., Riverside; Univ. of Cal., Riverside; Univ. of Cal., Riverside; Cal. State Univ. Northridge; Cal. State Univ. Northridge; Univ. of Cal., Riverside; ; : Muscle Glucose Transporters (GLUT-4 ) and Glycogen Storage of Mice Selectively Bred for High Activity Levels
To examine the microevolution of capacity for sustained exercise, we have selectively bred 4 replicate lines of house mice for high wheel running (High Runner or HR lines), while also randomly breeding 4 lines as controls (C). Here, we report initial studies of carbohydrate use and accumulation during voluntary wheel running. We sampled females from gen. 35 at three times on the 6th day of wheel access (4 PM, 2 AM [during peak running], 7 AM; lights on 7 AM – 7 PM). Females from gen. 37 that never had wheel access were also sampled to determine whether any differences between HR and C lines could be a short-term effect of the former’s elevated wheel running. HR individuals with the mini-muscle phenotype (homozygous for a Mendelian recessive allele that halves gastrocnemius muscle mass while doubling per gram aerobic capacity [Am. J. Physiol. 284:R433-R443]) were distinguished for statistical analyses comparing three types of mice: C, HRnormal, HRmini. Liver [glycogen] was similar in all three groups and increased from 4 PM to 2 AM to 7 AM, but with a somewhat different time course. Soleus [glycogen] differed as HRmini > HRnormal > C. All groups showed a decrease from 4 PM to 2 AM, followed by a rebound from 2 to 7 AM, but with significant group differences in the magnitude of these changes. Gastrocnemius [glycogen] differed as HRmini > HRnormal > C. However, C and HRnormal showed an increase from 4 PM to 2 AM to 7 AM, whereas HRmini showed a corresponding decrease. Without wheel access, no differences in gastrocnemius [GLUT-4] were observed. With wheel access, all mice showed elevated [GLUT-4], but HRnormal and HRmini showed a much greater [GLUT-4] than did C. NSF IBN-0212567 to TG and NIH GM-48680 and GM-08395 to BBY.
