Activity of Enzymes of Glycogen Metabolism in the Reproductive Tract of the Ewe at Mating and during Early Pregnancy

O’Shea, Tim; Murdoch, BE

doi:10.1071/bi9780355

Cited by 11 publications

(8 citation statements)

References 17 publications

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“…2 ). These findings agree with those for animals that do not exhibit obligatory embryonic diapause such as rodents [ 12 ], cats [ 28 ], ferrets [ 29 ], and sheep [ 30 ], illustrating that uterine glycogen reserves are a potential source of energy for uterine and pre-embryonic growth through implantation and early pregnancy.…”

Section: Discussionsupporting

confidence: 85%

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Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy

Dean

Hunt

McDougall

et al. 2014

Journal of Reproduction and Development

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We have determined uterine glycogen content, metabolizing enzyme expression and activity in the mink, a species that exhibits obligatory embryonic diapause, resulting in delayed implantation. Gross uterine glycogen concentrations were highest in estrus, decreased 50% by diapause and 90% in pregnancy (P ≤ 0.05). Endometrial glycogen deposits, which localized primarily to glandular and luminal epithelia, decreased 99% between estrus and diapause (P ≤ 0.05) and were nearly undetectable in pregnancy. Glycogen synthase and phosphorylase proteins were most abundant in the glandular epithelia. Glycogen phosphorylase activity (total) in uterine homogenates was higher during estrus and diapause, than pregnancy. While glycogen phosphorylase protein was detected during estrus and diapause, glycogen synthase was almost undetectable after estrus, which probably contributed to a higher glycogenolysis / glycogenesis ratio during diapause. Uterine glucose-6-phosphatase 3 gene expression was greater during diapause, when compared to estrus (P ≤ 0.05) and supports the hypothesis that glucose-6-phosphate resulting from phosphorylase activity was dephosphorylated in preparation for export into the uterine lumen. The relatively high amount of hexokinase-1 protein detected in the luminal epithelia during estrus and diapause may have contributed to glucose trapping after endometrial glycogen reserves were depleted. Collectively, our findings suggest to us that endometrial glycogen reserves may be an important source of energy, supporting uterine and conceptus metabolism up to the diapausing blastocyst stage. As a result, the size of uterine glycogen reserves accumulated prior to mating may in part, determine the number of embryos that survive to the blastocyst stage, and ultimately litter size.

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Section: Discussionsupporting

confidence: 85%

“…Glycogen may also be degraded intra-luminally, as glycogen granules contain anabolic and catabolic enzymes. As evidence, glycogen phosphorylase activity in sheep uterine luminal fluids increased during pre-implantation, peaking near the expected time of implantation [ 30 ].…”

Section: Discussionmentioning

confidence: 99%

Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy

Dean

Hunt

McDougall

et al. 2014

Journal of Reproduction and Development

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“…Gluconeogenesis does not occur in the uterus (Zimmer & Magnuson, ; Yánez et al, ) and glucose in uterine secretions is derived from the maternal circulation and/or catabolism of uterine glycogen reserves (Demers, Yoshinaga, & Greep, ; Leese et al, ). In sheep and rodents, uterine glycogen concentrations peak during pro‐estrus and estrus, and are mobilized during implantation and pregnancy (Demers et al, ; O'Shea & Murdoch, ). In mink, uterine glandular and luminal epithelial glycogen concentrations were highest during estrus and decreased 99% by the peri‐implantation period (Dean, Hunt, McDougall, & Rose, ).…”

Section: Introductionmentioning

confidence: 99%

Activation of the IGF1 receptor stimulates glycogen synthesis by mink uterine epithelial cells

Dean

Rose

2018

Molecular Reproduction Devel

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Glycogen synthesis by mink uterine epithelial cells is stimulated by estradiol (E ) during estrus, although the mechanism/s through which the steroid promotes glycogen accumulation are unknown. Our aim was to determine if insulin is required for E induced glycogen synthesis by an immortalized mink uterine epithelial cell line (GMMe). We show that the cells expressed the genes for glycogen metabolizing enzymes (hexokinase 1, glucose-6-phosphatase 3, glycogen synthase 1, and glycogen phosphorylase-muscle), receptors for insulin, insulin-like growth factor 1 and E (Esr1). Interestingly, treatment of cells with E alone failed to stimulate glycogen production, whereas supraphysiological concentrations of insulin (50 μg/ml) only, significantly increased glycogen content. Moreover, insulin + E increased glycogen content when compared to insulin alone (p < 0.05), an affect that was blocked when cells were treated with the pure E receptor antagonist ICI 182,780. Glycogen synthesis in response to insulin was significantly inhibited when cells were pre-treated with picropodophyllotoxin, an IGF1R antagonist. Treatment of cells with LY294002, a phosphatidylinositol 3-kinase (PI3K) antagonist, blocked insulin's effects on glycogen production whereas treatment with U0126, an inhibitor of mitogen activated kinase-kinase (MEK1/2) was without effect. These findings suggest to us that the affects of E on glycogen synthesis by GMMe cells is mediated through Esr1 and increased responsiveness of the cells to insulin. Because picropodophylotoxin blocked the effects of insulin on glycogen production, and both insulin and IGF1 act through PI3K, it is possible that IGF1 plays a role in glycogen production by these cells.

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“…This was despite a high level of glycogen synthase. The increase in oviducal IX-amylase activity at oestrus did not reach significance, but studies on pregnant ewes have shown a steady decrease after oestrus in IX-amylase activity in the oviduct (O'Shea and Murdoch 1978a). Thus the two catabolic enzymes measured had different patterns during the oestrous cycle with total glycogen phosphorylase showing a rise from day 1 to day 8, whereas IX-amylase showed maximum activity at day O.…”

Section: Discussionmentioning

confidence: 88%

Activity of Enzymes in the Mucosal Tissues and Rinsings of the Reproductive Tract of the Naturally Cyclic Ewe

Murdoch¹,

O’Shea²

1978

Aust. Jnl. Of Bio. Sci.

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The activity of several enzymes has been measured in the oviducal mucosa, endometrium, caruncles, cervical mucosa and vaginal mucosa as well as in uterine, cervical and oviducal rinsings of ewes at days 0 (oestrus), 1, 8 and 15 of the oestrous cycle.Acid phosphatase activity was maximal during the luteal phase in the oviduct, endometrium and cervix, but not in the vagina where the highest level was on day 1. Alkaline phosphatase activity showed a significant rise at mid-cycle in the endometrium and caruncles as did glucose-6-phosphate dehydrogenase activity in the endometrium.Glycogen (starch) synthase in the endometrium and cervical mucosa was greater at days 0 and 8 than at days 1 and 15. Vaginal and caruncular total glycogen (starch) synthase activity showed a significant rise at mid-cycle. Active and total glycogen phosphorylase activities were maximal on days 8 and 15 in the vagina. Glycogen concentration was greatest at days 8 and 15 in the cervix, while oviduct values were lower on day 1 than at oestrus or day 15.In the oviduct rinsings alkaline phosphatase activity was greatest at day 1, whereas in cervical rinsings the activities of acid and alkaline phosphatases were less at oestrus than at days 8 and 15. The glycogen phosphorylase and p-glucuronidase activities in uterine rinsings were greater at days 8 and 15 than at oestrus.

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Activity of Enzymes of Glycogen Metabolism in the Reproductive Tract of the Ewe at Mating and during Early Pregnancy

Cited by 11 publications

References 17 publications

Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy

Uterine glycogen metabolism in mink during estrus, embryonic diapause and pregnancy

Activation of the IGF1 receptor stimulates glycogen synthesis by mink uterine epithelial cells

Activity of Enzymes in the Mucosal Tissues and Rinsings of the Reproductive Tract of the Naturally Cyclic Ewe

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