Leukocyte mobilization induced by hypervolemia is due to a combined alpha-and beta-adrenoceptor activation

A phenomenon of leukocytosis induced by hypervolemic stress was discovered. Although a single injection of 350 mul of saline (equivalent to approx. 70 mi in humans, I ml/kg of body weight) did not have an effect on the leukoc yte counts in long-term intravenously cannulated, freely behaving rats, a s ingle injection of 750 mul of saline (equivalent to approx. 150 mi in human s, 2.1 ml/kg) induced rapid leukocytosis of 160% within I minute followed b y a gradual increase up to 180% after 1 hour. Measurement of serum norepine phrine concentration revealed a significant increase in rats of the hypervo lemic group, compared with those of the low volume group. Pretreatment with either the beta -adrenoceptor antagonist nadolol or the selective alpha (2 )-adrenoceptor antagonist yohimbine prevented both leukocyte peaks in the h igh volume group, suggesting a combined receptor activation. This critical dependence of leukocyte counts on changes in blood volume should be taken i nto consideration in experiments with laboratory animals (the quantity of v olume applications can falsify results of experiments).