Episodic secretion of vasopressin in man

The plasma arginine vasopressin concentration (pAVP) was measured in blood samples obtained from an internal jugular vein of 8 patients who underwent surgery for a carotid artery stenosis. Ten blood samples were taken with 1 min interval during the operation. Arterial pAVP was measured in 10 simultaneous samples from a radial artery and the brain venoarterial difference of pAVP was calculated. The venoarterial difference was 0-3 pg/ml in 7 of the patients, while it increased to 35 pg/ml upon baroreceptor stimulation in one patient. A pulsatile pattern was found in the veno-arterial difference of pAVP both at low and higher peripheral pAVP levels. This appeared to reflect a discontinuous release of AVP from the neurohypophysis. The described method results in a more accurate picture of ongoing secretory activity than can be obtained by measurements of peripheral pAVP alone. The general usefulness of the method, however, is restricted by the need of a multitude of samples and the difficult approach to the internal jugular vein.