[Regional changes in endothelin levels in venous and arterial blood in a limb subjected to postural variations]

The aim of this study was to evaluate the behaviour of plasma endothelin in humans both in venous and arterial blood at the level of a limb subjected to postural changes. An experimental model was designed for this purpose in which tissue hypoperfusion conditions were created in a subject lying on his back by maintaining an upper limb in a vertical position for approximately one hour. The limb was then lowered and remained horizontal for another hour. The study was performed in 5 healthy subjects aged between 59 and 75 years old. Both venous and arterial blood samples were collected, virtually contemporaneously, at times 0.60 and 120 minutes, namely before and after raising the limb and after the limb had been lowered for one hour. Mean endothelin levels +/- SD in arterial blood were respectively 3.36 +/- 1.29 pg/ml, 4.13 +/- 1.16 pg/ml and 3.82 +/- 1.11 pg/ml at times 0.60 and 120 min. Mean endothelin levels SD in venous blood at the same times were respectively 3.84 +/- 1.41 pg/ml, 5.62 +/- 2.26 pg/ml and 4.95 +/- 1.39 pg/ml. In both arterial and venous blood, the difference between the first two values was statistically significant (p < 0.05). Endothelin therefore appears to be affected by changes in district hemodynamics.