Putative precursors of vasopressin, oxytocin, and neurophysins in the rat hypothalamus.

The biosynthesis of [arginine8]vasopressin (AVP) and oxytocin (OT) was studied, and the results obtained have been compared with a study of their associated neurophysins (NP), AVP-NP and OT-NP. Rat hypothalamic extracts obtained at acid pH were subjected to Sephadex G-75 gel filtration chromatography and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). Fractions of gel chromatography effluent and extract of SDS-PAGE gel slices were subjected to RIA for immunoreactive precursors of AVP, AVP-NP, OT, and OT-NP using specific antisera fro each molecule. Tritiated bovine serum albumin, ovalbumin, and cytochrome c were used as internal standards during gel filtration chromatography and SDS-PAGE. Molecular weight estimates obtained for precursors of AVP were more than 70K, 31K, 13K, 5K, and less than 5K (AVP) by G-75 chromatography and more than 70K, 39K, 15K, and less than 5K (AVP) by SDS-PAGE. Molecular weight estimates obtained for precursors of AVP-NP were more than 70K, 35K, 24K, and 12K (AVP-NP) by G-75 chromatography and 19K and 10K (AVP-NP) by SDS-PAGE. Molecular weight estimates of OT were more than 70K, 35K, 19K, 8K, and less than 5K (OT) by G-75 chromatography and 60K, 35K, 19K, 9K, and less than 5K (OT) by SDS-PAGE. Precursors of OT-NP were estimated to be more than 70K, 17-18K, and 10K (OT-NP) by G-75 chromatography and 28K, 18K and 10K (Ot-NP) by SDS-PAGE. These studies show that there are small differences in precursor processing among AVP, AVP-NP, and OT, OT-NP, but allow for the existence of common precursors for AVP and AVP-NP and for OT and OT-NP.