Arginine vasopressin and oxytocin in the porcine corpus luteum

The relationship between ovarian oxytocin (OT), vasopressin and progesterone, was determined in porcine corpora lutea collected at various stages of the estrous cycle. Fractionation by reverse phase high performance liquid chromatography (HPLC) of extracts from mid-cycle corpora lutea showed the presence of arginine vasopressin-like (AVP) material, but not lysine vasopressin-like (LVP) activity. The tissue content of progesterone reached maximal amounts at mid-luteal phase, and decreased rapidly at the end of the cycle. However, tissue concentration of progesterone was the highest in early luteal phase. OT content was unchanged throughout the luteal phase of the cycle but declined at the end of the cycle. Tissue concentration of OT decreased from early in the cycle but was still measurable in the corpus albicans. Changes of AVP content and concentration were substantially the same as that of OT, except for a significant increase in AVP concentrations at the end of the cycle. These data confirm the presence of Ot, indicate the dominant presence of AVP and suggest that both hormones may be involved in porcine CL function.