AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 6 1400-R1405, Copyright © 1989 by American Physiological Society
Homologous regulation of human platelet vasopressin receptors does not occur in vivo
D. Vittet, J. M. Launay and C. Chevillard
Institut National de la Sante et de la Recherche Medicale U 300, Faculte de Pharmacie, Montpellier, France.
Large variations in the functional responsiveness of human platelets to
arginine vasopressin (AVP), related to maximal platelet AVP-binding
capacity, have been observed among individuals. The effects of dehydration
and overhydration on maximal platelet AVP-binding capacity, plasma AVP,
platelet-associated AVP, and AVP-induced platelet aggregation were examined
in healthy human volunteers to determine whether homologous regulation of
platelet AVP receptors occurs in vivo within the physiological range of
circulating AVP fluctuations. Although significant variations of plasma AVP
were observed under both conditions, no correlation could be found in the
same individual with any change in 1) the maximal AVP-binding capacity, 2)
platelet aggregatory responses to AVP, or 3) the platelet AVP fraction.
Moreover, there was no relationship between the number of detectable
platelet AVP receptors and the amount of AVP associated with platelets.
These data show that homologous regulation of platelet AVP receptors by AVP
does not occur in vivo over the time investigated, at least within the
physiological range of AVP. Nonetheless, regulation at the platelet
precursor stage appears to be highly probable in view of the relationship
between plasma AVP and platelet AVP binding capacity observed among
different individuals.
