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BACKGROUND: This study combines two factors of winter swimming, regular swimming and cold-adaptation, to mimic winter swimming in rats. The effects of winter swimming on hemorheology and NO and NOS of aorta were studied, and the mechanism was discussed.MATERIALS and METHODS: Use 30 SD rats, 10 months old and avoirdupois 185±15g. The rats were raised in the temperature of 20±3℃, relative humidity of 50±5% and 3～4 rats per cage with natural lighting and free food and water. After 3 days’breeding, they were randomly separated into 3 groups, 10 rats in the control group, 10rats in the cold stimulation group and 10rats in the cold-adaptation group. In the control group, the rats with no exercise were killed in the 7th week. In the cold stimulation group, the rats without exercises until the end of 6th week were trained to swim 3 days, exercised in the 8℃water 8 mins in the 7th week, and then were killed immediately. In the cold-adaptation group, the rats were trained to swim 3 days, and then went into formal exercises for 6 weeks. In the 7th week, they swam in the 8℃water 8 mins and then were killed immediately. These cats were termly weighed every week. Collect the blood by Cutting Rats’ heads, which was infused into EDTA-anticoagulant tubes and sent to do clinic hemorheological index tests in the clinical laboratory of the Second Affiliated Hospital of Dalian Medical University. Separate the aorta quickly right after opening the abdominal cavity of rats and use NOS Kit and NO Kit to do Biochemistry detection.RESULTS: The cold-adaptation group had a good condition, and the gain weight was markedly lower than the other two group(sP<0.01). In the cold stimulation group, the whole blood viscosity (low, medium and high shear) and the reduced viscosity of whole blood (low, medium and high shear) both had an increasing trend, and the reduced viscosity of whole blood increased significantly(P<0.01); in the cold-adaptation group, the whole blood viscosity (low, medium and high shear) and the reduced viscosity of whole blood (low, medium and high shear) were both ameliorated, and especially the reduced viscosity of whole blood was improved significantly(P<0.01). In the cold stimulation group, the aggregative index of red blood cell (AIRBC), the erythrocyte deformation index (EDI) and the rigidity index (RI) all increased significantly (P<0.01); in the cold-adaptation group, the AIRBC, EDI and RI were all ameliorated(P<0.01). In the cold stimulation group, the hematokrit, the red-cell count and the hemoglobin all had a downtrend; instead in the cold-adaptation group, the hematokrit, the red-cell count and the hemoglobin all had an uptrend. But they were all not significant(P>0.05). In the cold stimulation group, the stress yield, the Casson viscosity and the erythrocyte electrophoretic time all raised; in the cold-adaptation group, these figures all had a catabatic trend. But they were both not significant(P>0.05). In the cold stimulation group, the NO content reduced, but was not significant(P>0.05); instead in the cold-adaptation group, the NO content increased(P<0.05). In the cold stimulation group, the activity of TNOS and iNOS had a downtrend; instead in the cold-adaptation group, the activity of TNOS and iNOS increased significantly(P<0.01).CONCLUSIONS:The winter swimming sport with the cold-adaptation training can effectively resist the increase of blood viscosity caused by cold stimulation, and enhance the erythrocyte deformability. It may also help to improve the NO content and NOS activity of aorta, to control the increase of body weight, and to keep in good form.
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