Swelling of sarcoplasmic reticulum in the periphery of muscle fibres after isometric contractions in rat semimembranosus lateralis muscle
Abstract:The decline in isometric force, swelling of sarcoplasmic reticulum and loss of desmin was measured in semimembranosus lateralis muscle of male Wistar rats immediately after a short series of brief (500 ms) maximal isometric contractions. For the active muscle, the series ended below (protocol A) and just over muscle optimum length (protocol AA). In one protocol, the muscle remained passive and was extended to lengths just over muscle optimum length (protocol P). After all experimental protocols, no loss of desmin was observed and sarcomere appearance was normal. Protocol A produced swelling (87%) of the sarcoplasmic reticulum but no decline in isometric force. Protocol AA produced larger swelling (147%) of the sarcoplasmic reticulum and an isometric force decline (<49%) at short muscle lengths. Swelling of sarcoplasmic reticulum was observed mainly in the periphery of muscle fibres. Protocol P did not result in swelling of the sarcoplasmic reticulum and isometric force decline. It is concluded that swelling of the sarcoplasmic reticulum in the periphery of muscle fibres after brief maximal isometric contractions is associated with muscle force and not muscle length.
Document Type: Research Article
Affiliations: 1: Department of Physiology, West Virginia University, West Virginia, USA 2: Institute of Fundamental and Clinical Human Movement Sciences, Free, University, the Netherlands 3: Department of Hand Surgery, Sahlgrenska University Hospital, Gothenburg, Sweden
Publication date: April 1, 1999