Stanniocalcin 1 (STC1) is a
glycoprotein that decreases
calcium and increases
phosphate in cells/tissues. This investigation examined endocrine regulation of STC1 in endometria of pigs during the estrous cycle and pregnancy. STC1
mRNA was present exclusively in
luminal epithelium (LE) between d 12 and 15 of the estrous cycle, increased between d 12 and d 20, and was not detectable by d 30 of pregnancy. STC1
protein was also detected in uterine
flushings. To determine effects of
estrogen and
progesterone, pigs were ovariectomized and treated with these
hormones alone or together.
Progesterone, but not
estrogen, induced STC1 in LE. Cotreatment with
progesterone and
estrogen further stimulated STC1 over
progesterone alone. To determine effects of pseudopregnancy, nonpregnant gilts were given daily
injections of
estradiol benzoate from d 11 to d 14. STC1 was not expressed in LE on d 90 of pseudopregnancy, suggesting that the
estradiol given to induce pseudopregnancy and/or long-term exposure to
progesterone are required for down-regulation of STC1. To determine effects of long-term
progesterone, without effects of
estradiol, pigs were ovariectomized on d 12, given daily
injections of
progesterone through d 39, and hysterectomized on d 40 after estrus. STC1 was expressed in LE of
progesterone-treated pigs, suggesting that
estrogen is involved in down-regulation of STC1. We conclude that STC1 is induced in LE by
progesterone and further stimulated by
estrogen, and its down-regulation in LE by d 25 likely requires exposure of the progestinized uterus to
estrogen. The temporal and cell type-specific expression of STC1 makes this gene a unique marker for implantation in pigs.