The Effect of Oxytocin and Vasotocin upon Progesterone, Testosterone and Estradiol 17β-Secretion by the Luteal Cells from Cyclic Pigs

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Abstract
Porcine luteal cells were obtained from the corpora lutea on the 13th day of the estrous cycle. The cells were digested with 0.25% trypsin and suspended in the Medium 199 with an addition of 10% calf serum, at a concentration of 5 x 104 cells/ml. The cells were incubated with or without 4 and 40 mi.u./ml of oxytocin, 10 and 100 ng/ml of arginine-vasotocin, 1 µg LH and 50 U/ml hCG. Levels of progesterone, testosterone and estradiol 11 β were determined with the radioimmunological method, following 6 h incubation. It was found that progesterone secretion under the influence of oxytocine (4 mi.u./ml) was less than in the control group and in the group with LH. Similarly, arginine-vasotocin at a dose of 10 ng/ ml inhibited progesterone secretion (P < 0.05). Higher doses of these peptides had no suppressive effect on the luteal cells. Oxytocin and arginine-vasotocin had no influence on testosterone secretion by luteal cells. However, these cells produced less (P < 0.05) estradiol 17β under the influence of oxytocine than of hCG. The results point to a direct effect of oxytocin and arginine-vasotocin on steroidogenesis in the corpora lutea of cyclic pigs.