Acid extracts of corpora lutea collected from nonpregnant cows were found to contain oxytocin, arginine vasopressin, and neurophysin. The inhibition curves of the oxytocin and vasopressin extracts showed parallelism with the appropriate standard preparations in specific RIAs 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. However, its immunoreactive profile on HPLC differed slightly from that obtained with hypophyseal bovine neurophysin I. In nonpregnant cows the oxytocin content (about 1 microgram g-1 wet wt of tissue) was three orders of magnitude greater than the vasopressin content. Levels of luteal oxytocin were considerably lower in pregnant animals. These results show that the bovine ovary is a rich source of neurohypophysial peptides and suggest that oxytocin biosynthesis may occur within the corpus luteum.

Cell cycle entry is prevented in aortic tissue, and this is associated with an inability to downregulate p16 and p27 CKIs, and therefore to activate cyclin D1 and cyclin E associated kinase activities.

In this report we demonstrate that ovine and bovine luteal cells synthesise oxytocin by way of a precursor protein similar to that found in the hypothalamus. Isolated ovine or bovine luteal cells were incubated for up to 12 h with [TS]cysteine. Neurophysin-Sepharose column separation and HPLC of cell extracts demonstrated the presence of [%]oxytocin. Incorporation of [%]cysteine was confirmed by performic acid oxidation. Immunoprecipitation of cell extract with anti-rat oxytocin-neurophysin followed by SDS-PAGE yielded 2 radioactive bands of 14 kDa and 1 l-12 kDa. Immunoprecipitation with anti-oxytocin yielded 1 band at 14 kDa. On SDS-PAGE the 14 kDa band had a similar mobility to rat-hypothalamic oxytocin precursor.

No abstract

The discovery of oxytocin in the corpus luteum of the ovary,' and the subsequent confirmation that it was biosynthesized by luteal cells2 using an mRNA very similar to that produced in the hypothalamus,' directed attention to the gonads as nonneuronal sites of "neurohypophyseal hormone" production. This paper focuses on the nature, location, and possible functions of oxytocin-like peptides in the testis. Oxytocin-Like Peptides in the TestisAs can be seen from TABLE 1, radioimmunoassays of acid extracts of testis tissue from different species, using an oxytocin-antiserum that showed little cross-reactivity with several related peptides, consistently detected significatlt levels of immunoreactive oxytocin. Moreover, a molecule having the immunoreactive properties of neurophysin could be detected in man and rat! In addition, testis extracts from a bird (Japanese quail) in which the organ is photoperiodic were found to contain a mesotocin-like peptide that was augmented when the testis was stimulated to grow by transferring the animals from short to long days.'When testis extracts were chromatographed by HPLC, the oxytocin immunoreactivity was associated with a component having the same chromatographic characteristics as authentic oxytocin. However, different "specific" antisera for oxytocin gave different quantitative estimates of the peptide and, indeed, some antisera recognized an additional peak eluting from the HPLC column just before authentic oxytocin (FIG.