Regional and fibre type glycogen utilization patterns in the hamster diaphragm following swimming

The purpose of this study was to determine the regional and myofibrillar ATPase (M-ATPase) fibre type glycogen utilization patterns in response to increased ventilation induced by pre-exhaustive (Pre-Exh) and exhaustive (Exh) durations of swimming. Twenty-eight hamsters were studied: six controls (Con), 11 Pre-Exh (swam 82 min), 11 Exh (swam to exhaustion). We examined the optical density of PAS-stained fibres from the different regions of the diaphragm as a measure of glycogen remaining after the exercise or control period. The optical densities of PAS-stained fibres in most M-ATPase fibre types and diaphragmatic regions for the Pre-Exh and Exh groups was less than those in the Con hamsters except for the optical densities of all the M-ATPase fibre types in the sternal region. The optical densities of PAS-stained fibres in different regions and M-ATPase fibre types did not differ in the Exh and Pre-Exh groups. This data indicates that significant glycogen utilization occurred in all three M-ATPase fibre types in the costal, and both the thoracic and abdominal surface of the crural diaphragm in hamsters following pre-exhaustive and exhaustive durations of swimming. Glycogen utilization was greater in type 1 fibres of the thoracic surface of the crural region than in the type 1 fibres of the sternal region of the Pre-Exh group. Further, significant utilization of glycogen did not occur in any of the three M-ATPase fibre types of the sternal region of the diaphragm following prolonged durations of swimming. It would appear that glycogen is an important substrate in the hamster diaphragm during swimming.(ABSTRACT TRUNCATED AT 250 WORDS)