A partial cDNA which encodes the rat homolog of human placental protein-12, the low mol wt insulin-like growth factor-binding protein (IGFBP-1), has been isolated from a rat decidual cDNA library using low stringency hybridization with a human IGFBP-1 cDNA probe. The incomplete cDNA obtained from this library was used to screen a rat liver cDNA library from which a full-length cDNA was obtained. The predicted amino acid sequence of rat IGFBP-1 showed 66%, 29%, and 34% sequence identity with the human IGFBP-1, the human GH-dependent binding protein IGFBP-3, and rat IGFBP-2, the BP secreted by buffalo rat liver cells, respectively. The rat IGFBP-1 cDNA hybridized with a 1.6-kilobase transcript which was easily detected in uterine RNA from the pseudopregnant rat and RNA from the liver and kidney of adult rats. A low level of expression was apparent in the brain and the diestrous uterus. Of the tissues examined the order of abundance of IGFBP-1 mRNA was deciduoma tissue greater than or equal to liver much greater than kidney much greater than uterus greater than brain. The 1.6-kb mRNA was more abundant in RNA from neonatal rat liver than in that from maternal liver, but was not detected in total RNA (50 micrograms) from other neonatal rat tissues (kidney, lung, brain, and heart). Under stringent conditions, rat IGFBP-1 did not hybridize with RNA from the BRL-3A rat liver cell line. In food-deprived rats, hepatic IGFBP-1 mRNA was increased 10.0 +/- 2.2-fold compared to that in control rats.(ABSTRACT TRUNCATED AT 250 WORDS)

A full-length cDNA clone for rat placental lactogen I (rPL-I) has been isolated from a phage lambda gt11 library containing cDNA synthesized from day 11 rat placental mRNA. By Northern blot analysis the rPL-I cDNA clone hybridizes to a 1.0-kilobase placental mRNA and appears as early as day 10 of gestation. Maximal expression of this mRNA was observed in day 11 and 12 placenta, and faint hybridization of the rPL-I cDNA was also detected in day 18 to term placenta. In contrast, the mouse clone hybridized to mRNA for mouse PL-I (mPL-I) only in day 10 mouse placenta (9). In vitro translation of rPL-I mRNA produced by transcription of the cDNA template yielded a 27-kDa polypeptide the size of the expected precursor protein which was immunoprecipitated by a monoclonal antibody to rPL-I. The rPL-I cDNA nucleotide sequence has been determined. The sequence is very similar to that for mPL-I and contains an open reading frame encoding a polypeptide of 230 amino acids compared to 224 for mPL-I. Comparison of the predicted primary translation product of rPL-I mRNA with that of mPL-I mRNA revealed that rPL-I shares 73% identity to mPL-I at the amino acid level. The predicted rPL-I protein shares 41% amino acid identity with rPL-II precursor, 24% with rat prolactin-like protein A, 26% with rat prolactin-like protein B, and 31% with rat PRL. In situ hybridization studies indicated that mRNA for rPL-I was present in a few rapidly dividing cells as early as day 8 of gestation, and by day 9 could be localized to giant cells which surround the conceptus.

Decidualization of the uterus involves proliferation and differentiation of uterine cells. The effects of decidualization on uterine expression of insulin-like growth factor-I (IGF-I) and IGF-binding protein-1 (IGFBP-1) have been examined in the hypophysectomized-ovariectomized (hypox-ovx) rat and the pituitary-intact (ovx) rat. Decidualization was induced by uterine stimulation of animals treated with a combination of 17 beta-estradiol and progesterone. The patterns of change in uterine IGF-I mRNA and IGFBP-1 mRNA abundance were similar to hypox-ovx rats, hypox-ovx rats replaced with GH and T4, and ovx rats. The changes in IGF-I mRNA abundance were temporally related to 17 beta-estradiol injections. IGFBP-1 mRNA was undetectable early in the decidualization process and reached maximal levels on day 6. Mechanical separation of the deciduoma tissue from the underlying myometrium revealed that the deciduoma tissue was depleted in IGF-I mRNA, while the majority of the IGFBP-1 was located in the deciduoma tissue. The in situ hybridization technique was used to localize IGF-I and IGFBP-1 mRNA in the decidualized uterus. The majority of the IGF-I expression was localized to the outer stroma and smooth muscle cell layer, whereas IGFBP-1 mRNA was detected in uterine epithelial cells and stromal glands. These experiments demonstrated that uterine IGF-I and IGFBP-1 expression during the process of decidualization are pituitary independent. Furthermore, our observations support the hypothesis that the expression of IGFBP-1, a protein capable of inhibiting the mitogenic activity of IGF-I, in deciduoma tissue may inhibit paracrine IGF-1 actin and allow for the differentiation of stromal tissue.

The ovulation-inducing property of androgens in the laying hen was investigated. In a first experiment, four different androgens were injected subcutaneously into single-comb White Leghorn hens on the day of the last oviposition of a sequence. The hens were killed 10 h later and examined for the presence of an ovum in the oviduct. Testosterone induced ovulation in accordance to the dose injected (median effective dose, 966 +/- 193 microgram/hen) but the responses to 5 alpha-dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol were not dose-related. The effect of 4-androstene-3, 17-dione was more like that of progesterone since it induced ovulation 2 h earlier than the three other androgens. The physiological significance of the ovulation response to an injection of testosterone was examined in more detail in experiment 2. Seven out of ten hens which were injected with 1 mg testosterone/kg body weight ovulated within 10 h after the injection. Blood samples were taken at hourly intervals and the concentrations of testosterone and progesterone were determined by radioimmunoassay. An injection of testosterone produced an increase in the concentration of testosterone in plasma which was considerably greater and occurred earlier than the preovulatory increase of testosterone in the control birds. The increase in the concentration of progesterone in the hens injected with testosterone was similar in magnitude but occurred earlier than the spontaneous preovulatory increase of progesterone in the control hens. The possible physiological role of testosterone in the ovulation cycle is discussed.