Patterns of plasma progesterone, androgen and oestrogen concentrations and in-vitro ovarian steroidogenesis during embryonic diapause and implantation in the mink (Mustela vison)

Abstract

Summary. Peripheral plasma progesterone concentrations exhibited an increase 10 days before implantation, coinciding with the resumption of blastocyst growth and with a decrease in plasma androgen values (DHA, androstenedione, testosterone). No definite pattern of oestrone was observed and oestradiol concentrations remained undetectable. The production of steroids by dispersed luteal cells showed that the growth of the corpora lutea paralleled that of blastocysts and resulted in hypertrophy followed by hyperplasia of the luteal cell. The production of progesterone in the medium increased with blastocyst size up to implantation; it was enhanced by mink charcoal-treated serum, but prolactin, LH, FSH or a combination of these hormones did not affect the progesterone production, whatever the stage of diapause. DHA and androstenedione secretion increased in the two last stages of blastocyst growth and was enhanced by LH. The conversion of androstenedione and testosterone into oestrone and oestradiol was observed at all stages of embryonic diapause, indicating that corpora lutea contain aromatase activity even at an early stage. The secretion of oestrone was higher than that of oestradiol. The non-luteal tissue contributed up to 50% of the steroid production; while progesterone and androgen production remained constant, that of oestradiol decreased at the end of the delay period. These results indicated a change in the size and the secretory capacity of the luteal cell related to blastocyst development and implantation. Although progesterone was the main product of the corpora lutea, androgens and oestrogens were also secreted.

Serum Progesterone and Estradiol-17.BETA. Concentrations in Captive and Free-Ranging Adult Female Japanese Black Bears (Ursus thibetanus japonicus).

“…Ravindra and Mead [17] described the relationship in the spotted skunk between changes in estrogen levels and blastocyst development in vivo, indicating that estrogen levels tended to decrease as the diameter of the blastocyst increased. Similar evidence was reported in an in vitro study of the mink [19]. However, it has not been determined precisely what the decrease in E2 signifies with regard to embryo development.…”

Histology of ovaries and uteri and levels of plasma progesterone, oestradiol-17β and oestrone sulphate during the implantation period in mated and gonadotrophin-releasing hormone-treated mink (mustela vison) exposed to polychlorinated biphenyls

“…Glandular diameters were larger in the GnRH-treated which also supports previous suggestions 8,23 that ovary/corpus luteum is the most probable source of control group than in the mated control group. On the first observation day both PCB-exposed and control oestrone in mink.…”

“…11 Several studies have shown that exposure of female the corpus luteum comprises luteal cell hyperplasia followed by hypertrophy. 8 Endocrine activation is mink to certain polychlorinated biphenyls (PCB) during gestation causes fetal death. [12][13][14][15][16][17][18][19][20] Ovulation, fertilization dependent on prolactin before implantation and and implantation occur, but fetuses die or are stillborn.…”

Embryonic diapause: development on hold

“…Multiple studies have shown that implantation is preceded by a rapid increase in circulating progesterone from the reactivated corpus luteum (Stoufflet et al, 1989;Murphy, 2012). Prolactin binds to membrane preparations from the anestrous mink uterus (Rose et al, 1983).…”