Arginine-vasopressin binding to isolated hippocampal microvessels of rats with different endogenous concentrations of the neuropeptide.

The binding of [125I]arginine-8-vasopressin (AVP) to hippocampal microvessels isolated from brains of normal Wistar rats, animals after water deprivation and heterozygous as well as homozygous diabetes-insipidus rats (Brattleboro strain) were measured. Data from binding experiments from the microvessels of the different groups of animals in each case revealed a single class of high affinity binding sites. However, the binding parameters between the different groups of rats were different. The affinity constants differs by a factor of 5.1, ranging from KD = 1.18 nmol X L-1 (animals after water deprivation) to KD = 6.05 nmol X L-1 (homozygous Brattleboro rats). The binding capacity, differing by a factor of 3.5, ranged from Bmax = 245 fmol X mg-1 to Bmax = 865 fmol X mg-1.