Gender Specific MAPK Responses in Murine Skeletal Muscle Following Six Bouts of Exercise

Abstract

MAPKs (ERK1/2, p38, JNK) participate in the cellular response to exercise. This study analyzed the gender specific role of MAPKs in murine biceps brachii after six bouts of eccentrically-biased downhill running. The MAPK response seen in both genders is lower in overall magnitude than the response following a single bout of the same exercise. Exercise-naive female and male mice (8–10 weeks old, n=5) ran six downhill (15°, 20 m/min) bouts. Muscles were analyzed for MAPK activity in a pre-exercise (PE) control (−1 hr) and at 9 timepoints post-exercise (PX). ERK1 in males and females showed a similar, but opposite response (1–2 fold change from PE levels); males increased activity from 0–12 hr PX and females decreased activity between 12 and 168 hr PX. ERK2 activity decreased in females for the entire time course (0 to 672 hr) after the 6 bouts, reaching minimum levels at 9 fold below PE at 3 hr PX, whereas males generally increased ERK2 activity through 24 hr PX. p38 activity in males was elevated through 168 hr PX, whereas females also exhibited a significant decrease in p38 activity (2 fold below PE) from12 to 672 hr PX. JNK activity increased in females following exercise from 0 to 24 hr PX with a peak in activity at 3 hr PX (3 fold above PE), then decreased to 3 fold below PE from 72 to 168 hr PX. In males, JNK activity increased following exercise (peaked at 6 hr PX 6 fold above PE), with a significant decrease in activity occurring at 48 hr PX (4 fold below PE). These results demonstrate that gender is a strong determinant in ERK1, ERK2 and p38; males significantly increase these activities, whereas females decrease them following 6 bouts of downhill running.