Adaptations to high-intensity intermittent exercise in rodents.

Area of Science:

• Exercise Physiology
• Molecular Biology
• Biochemistry

Background:

• Exercise-induced plasma volume (PV) expansion in humans is linked to increased albumin synthesis.
• Albumin synthesis is regulated at the transcriptional level.
• The effect of exercise on hepatic albumin gene expression in rodents is not well understood.

Purpose of the Study:

• To investigate the impact of a 12-day high-intensity intermittent exercise protocol on PV in rodents.
• To determine if exercise training increases hepatic albumin gene expression in rodents.
• To test the hypothesis that exercise training induces an increase in hepatic albumin gene expression.

Main Methods:

• Fifty male Sprague-Dawley rats were divided into control, sham exercise, moderate-intensity (MI), and high-intensity intermittent (HI) exercise groups.
• Plasma volume (PV) was measured 24 hours after the final exercise session.
• Hepatic albumin mRNA expression was quantified using real-time PCR.
• Citrate synthase (CS) activity in the quadriceps muscle was measured as a marker of aerobic adaptation.

Main Results:

• Citrate synthase (CS) activity increased with MI, HI, and single high-intensity (1-HI) exercise, indicating aerobic adaptation.
• No significant exercise-induced PV expansion was observed in the HI group compared to controls.
• Hepatic albumin mRNA expression significantly increased 2.9-fold after MI and 4.1-fold after HI compared to controls.
• A single bout of HI exercise did not alter hepatic albumin mRNA expression.

Conclusions:

• Twelve days of aerobic exercise training in rodents increases citrate synthase activity and hepatic albumin gene expression.
• Exercise training does not appear to induce significant plasma volume expansion in rodents under these conditions.
• There is a dissociation between exercise-induced increases in hepatic albumin gene expression and plasma volume expansion in rodents.