CALCYCLIN IN THE MOUSE DECIDUA - EXPRESSION AND EFFECTS ON PLACENTAL-LACTOGEN SECRETION

Placental lactogens are protein hormones produced by the placentas of many mammals. These hormones have diverse reproductive functions and a re structurally similar to the pituitary hormones growth hormone and p rolactin. Isolated decidual cells were previously shown to release a p rotein that stimulates mouse placental lactogen (mPL)-II release from mouse trophoblast cells in culture. Partial amino acid sequence data s uggested that this protein shared sequence identity with mouse calcycl in. In the present study the sequence identity of this protein was det ermined by sequencing reverse transcription-polymerase chain reaction (RT-PCR) products. The sequence matched that of mouse calcyclin. The d istribution of calcyclin message was determined in the conceptus by in situ hybridization, and a gestational profile of calcyclin mRNA was d etermined by Northern blot analysis. Calcyclin was localized primarily to cells that exhibited a uterine natural killer cell morphology with in the decidua and to glycogen cells of the labyrinth and junctional z one. Although calcyclin was detectable by RT-PCR in midterm placentas, isolated trophoblast cells in culture did not contain detectable quan tities of calcyclin by RT-PCR. Calcyclin stimulated secretion of mPL-I I from isolated trophoblast cells in vitro but did not affect mPL-I se cretion.