Specific D-glucose transport in sarcolemma vesicles.

Area of Science:

• Biochemistry
• Cell Physiology

Background:

• Sarcolemma is the cell membrane of muscle cells.
• Glucose transport across the sarcolemma is crucial for muscle energy metabolism.

Purpose of the Study:

• To characterize the D-glucose transport mechanism in rat skeletal muscle sarcolemmal vesicles.
• To investigate the effects of insulin, calcium, and other substances on glucose uptake.

Main Methods:

• Preparation of osmotically active sarcolemmal vesicles from rat skeletal muscle.
• Measurement of D-glucose and L-glucose uptake by the vesicles.
• Assessment of inhibition and enhancement of glucose transport by various agents.

Main Results:

• Sarcolemmal vesicles preferentially accumulate D-glucose over L-glucose via a saturable, stereospecific facilitated diffusion process.
• Glucose transport is inhibited by phloridzin, cytochalasin B, and certain sugars, and enhanced by counterflow.
• Insulin and calcium (in insulin-pretreated muscle) show a small enhancement of stereospecific D-glucose transport.
• Local anesthetics inhibit stereospecific glucose transport, while salt solutions increase apparent glucose uptake.

Conclusions:

• Rat skeletal muscle sarcolemma possesses a specific D-glucose transporter system.
• Insulin and calcium play a role in modulating glucose transport, albeit to a small extent in vitro.
• The experimental conditions, such as ionic strength, can influence the measurement of glucose uptake in vesicles.