| Research Abstract |
[Background] It is well known that exercise training is a potent stimulus to increase blood volume (BV), which is determined by many factors, i.e. renal water and Na^+ handling and fluid movement between the cellular and extracellular spaces. However, it remains unknown which factor is involved in the mechanism for the increase in BV due to exercise training.
[Purpose] 1. Treadmill exercise can increase BV in rats -rats could be model animal to investigate the mechanism for BV increase-?
2. Albumin, major substance maintaining plasma oncotic pressure, could be a factor increasing BV?
[Methods] Rats were divided into two groups : exercise training and no training groups (Ex and Con, respectively, n=10 each). The Con group was housed in normal cages at 23℃ in LD 12:12 h. The Ex group was also housed in the same condition but had 1-h treadmill exercise for 4 weeks (5 days/week). The treadmill speed was set at 10 m/sec and the slope was increased from 0°to 15°every week. At the end of 3rd wee
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k, two catheter were placed in the right femoral and jugular veins, respectively. In 5th week plasma volume (PV) of each rat was determined by Evans Blue dye dilution technique. Hematocrit, plasma albumin and total protein and oncotic pressure were also measured, and BV and plasma albumin content were calculated. Albumin synthesis was evaluated by measuring albumin mRNA level in the liver using Nothem blotting technique.
[Results] BV and plasma volume in the Ex group was greater (P<0.05) than in the Con group (6.4 ± 0.2 and 4.8 ± 0.5 ml/100g body weight, respectively). Plasma albumin content was also greater (P<0.05) than in the Con group (0.13 ± 0.01 and 0.10 ± 0.01 ml/100g body weight, respectively). The expression of albumin mRNA in the liver was similar in the two groups.
[Conclusion] Four-week treadmill exercise could increase BV in rats. The increase in plasma albumin could be a mechanism for this response. Although the expression of albumin mRNA in the liver remained unchanged between the Ex and Con groups, exercise training may have facilitated albumin synthesis in the earlier period. Less
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