A cytochemical bioassay for arginine vasopressin: preliminary studies.
A new method of measuring vasopressin activity is described. It depends on the finding that the Na+-K+-ATPase activity, measured cytochemically, in the thick ascending limb of the loop of Henle in rat renal tissue maintained in vitro, responded to increasing concentrations of synthetic arginine vasopressin in a log-dose related fashion. The limit of sensitivity was 0.002 pg/ml (2 x 10(-15) mol/l). The dose-responses were reproducible; the inter-assay coefficient of variation was 6.4% at a vasopressin concentration of 0.02 pg/ml. Normal plasma stimulated this Na+-K+-ATPase activity, the stimulation being reduced by 98% when the plasma had been treated with an antiserum specific for vasopressin. Measured in this system, the circulating levels of plasma vasopressin, in healthy adults after 18h dehydration, was 4.0 +/- 0.3 pg/ml (mean +/- SEM; n = 4) and fell to 0.6 +/- 0.1 pg/ml following a water load. Absolute plasma vasopressin values obtained by the cytochemical bioassay were comparable to those measured by radioimmunoassay (r = +0.97, p less than 0.001).
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000918:Antibody Specificity; D001127:Arginine Vasopressin / Q000097:blood; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D001127:Arginine Vasopressin; D000251:Adenosine Triphosphatases