| Abstract: | The purpose of this study was to evaluate the effects of body postural changes (supine-upright), upon the serum concentration of cholesterol (CT), triglycerides (TG), high density lipoproteins (HDL), low density (LDL) and very low density lipoproteins (VLDL) and hemoglobin, hematocrit, and plasma proteins (to calculate delta% change in plasma y volume). Nine healthy men participated as subjects. Their age ranged from 32 +/- 3 years old, and 16 +/- 4% body fat (X +/- SD). After 10-12 hours post absorptive and appropriate rest, they performed a standard orthostatic maneuver: subjects remained supine for 30 minutes, then assumed the standing position (unsupported and with minimal movement) for additional 30 minutes. Blood samples were obtained after 30 minutes supine and at 10, 20 and 30 minutes of standing. At 10 minutes of orthostatism, CT, TG, HDL and VLDL had a significant increase as compared to supine values; these changes were associated with a reduction of 8.9% on plasma volume (PV) (p less than 0.05). After 30 minutes of orthostatism CT, TG, HDL and VLDL showed increments of 8.5%, 33.3%, 20.1% and 32% respectively, in relation to the supine values (p less than 0.05). Changes on serum lipids were associated with PV reductions until 20 minutes of orthostatism. However, there was not a significant association between these variables at 30 minutes of standing. These data indicated that the body position and the time in which blood samples are obtained significantly influence lipid and lipoprotein serum level. Therefore, in any study related to lipids, such variables should be considered and properly controlled. |
