Muscle acetylcholinesterase adapts to compensatory overload by a general increase in its molecular forms

We have investigated the impact of compensatory overload on the content of acetylcholinesterase (AChe) molecular forms in the rat fast-twitch medial gastrocnemius (MG). Overload was induced by way of a bilateral tenotomy of the MG's functional synergists coupled to a daily walking training program (15 m/min, 30% incline, up to 60 min per session, 12-18 wks). This latter condition ensured that the MG were used on a regular basis. In comparison to control values, overloaded MG showed 25 and 19% increases (P less than 0.05) in muscle wet weight and protein concentration, respectively. The content in AChe (activity per muscle) was also increased in these MG (28%, P less than 0.05). Sedimentation analyses revealed a general elevation in the content of AChe molecular forms, with A8, G2, and G1 displaying significant changes (35-42%, P less than 0.05). In a second group of rats, daily running training (27 m/min, 30% incline, using the same timetable) was supplemented to the compensatory overload. In this group, the additional running training led to a greater hypertrophic response as attested to by increases (P less than 0.05) in the MG wet weight (41%) and protein concentration (35%) in comparison to controls. However, total AChe content of these muscles was increased to an extent similar to that observed in the MG subjected only to compensatory overload (24%, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)