[Effect of discontinuous hemorrhage on plasma and cerebrospinal fluid vasopressin concentration in anesthesized...

Repeated withdrawal of 15 ml arterial blood at 10 min intervals produced marked hypovolaemia and hypotension with plasma vasopressin concentration increasing exponentially from 53 microE/ml to more than 700 microE/ml contrary to the hypovolaemia. After the first blood withdrawal there exists a linear correlation between the increase of the plasma vasopressin concentration and the decrease of the mean arterial blood pressure. With 61.5 microE/ml the cerebrospinal fluid withdrawn following the last bleeding likewise showed a very high vasopressin level. After extraction of the hormone from plasma and cerebrospinal fluid the vasopressin concentration was determined by means of the antidiuretic bioassay in the water-loaded rat.