Characterization of Oxytocin, Vasopressin, and Neurophysin from the Bovine Corpus Luteum*

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Abstract
Acid extracts of corpora lutea collected from nonpregnant cows contained oxytocin, arginine vasopressin and neurophysin. The inhibition curves of the oxytoxin and vasopressin extracts showed parallelism with the appropriate standard preparations in specific RIA [radioimmunoassay], and eluted at the same position as the standards using high performance liquid chromatography (HPLC). The neurophysin extract showed parallelism in a bovine neurophysin I RIA and had a similar elution position to the standard on both Sephadex G-50 and HPLC. Its immunoreactive profile on HPLC differed slightly from that obtained with hypophyseal bovine neurophysin I. In nonpregnant cows the oxytocin content (about 1 .mu.g g-1 wet wt of tissue) was 3 orders of magnitude greater than the vasopressin content. Levels of luteal oxytocin were considerably lower in pregnant animals. The bovine ovary is a rich source of neurohypophyseal peptides and apparently oxytocin biosynthesis may occur within the corpus luteum.