Direct detection of the vasopressin precursor.

Cysteine-rich proteins were isolated from the hypothalamo-neurohypophyseal tract of dogs by high performance molecular weight chromatography. Trypsin digestion of these proteins produced a low molecular weight (LMW) peptide which was identified, by chemical and immunological assays, as (Arg8) vasopressin. There appear to be two forms of the precursor protein, one which has vasopressin immunoreactivity, and one which does not. Trypsin digestion of this latter protein produces high as well as LMW immunoreactivity. This suggests that the non-immunoreactive protein may be the precursor to the immunoreactive protein.