Arginine vasopressin release from human platelets after irreversible aggregation

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Abstract
1. The release of arginine vasopressin from human platelets was investigated in platelet-rich plasma after irreversible aggregation induced by adenosine 5''-pyrophosphate, collagen, sodium arachidonate, thrombin and adrenaline in vitro. 2. Arginine vasopressin levels were significantly higher in the supernatant from stimulated platelet-rich plasma than from unstimulated samples, reaching 3.5 .times. 10-12 (range 1.6-12.5 .times. 10-12) mol/l in the absence of an aggregating agent, 8.8 .times. 10-12 (range 4.2-17.5 .times. 10-12) mol/l after adenosine 5''-pyrophosphate, 13.7 .times. 10-12 (2.2-63.2 .times. 10-12) mol/l after collagen, 7.8 .times. 10-12 (2.2-14.6 .times. 10-12) mol/l after sodium arachidonate, 7.8 .times. 10-12 (2.2-16.3 .times. 10-12) mol/l after thrombin and 12.2 .times. 10-12 (4.8-32.1 .times. 10-12) moll after adrenaline. 3. An arginine vasopressin level of 18 .times. 10-12 moo/l, which can be achieved physiologically, increased the sensitivity of platelets to adenosine 5''-pyrophosphate and collagen in vitro; the same concentration of arginine vasopressin caused a potentiation of the effect of catehcolamines on the response of platelets to sodium arachidonate. 4. These results indicate that intraplatelet arginine vasopressin is released during aggregation and suggest that a local release of arginine vasopressin could occur after complete platelet aggregation in vivo.