Effects of recombinant bovine somatotropin (rbST) on ovarian and uterine function and the production of components of the insulin-like growth factor (IGF) system were examined during the period of maternal recognition of pregnancy in cattle. Lactating dairy cows were treated with 25 mg/d rbST (n = 8) or saline (n = 8) for 16 d after estrus. Ovaries, uteri, and conceptuses were collected on Day 17 after estrus. The length (millimeters) of the conceptus was recorded. The concentration of IGF-I and the content of IGF-binding proteins (BP) in uterine flushings were determined. Corpora lutea (CL) were weighed, and the number of follicles (> or = 2 mm in diameter) were counted. Follicular fluid from the largest and second-largest follicles was assayed for the concentration of IGF-I, IGFBP, progesterone, and estradiol. The length of the conceptus and the total amount of IGF-I in uterine fluid were similar for rbST and control. Recombinant bST increased 1) the weight of the CL, 2) the number of largest follicles (10 to 15 mm in diameter), 3) the concentration of IGF-I in the follicular fluid, 4) the follicular fluid content of IGFBP of the largest estrogenic follicle, and 5) the quantity of IGFBP in uterine flushings. The concentration of progesterone in the follicular fluid tended to be increased in rbST-treated cows, whereas the concentration of estradiol was similar to that of control cows. The concentration of progesterone in plasma was similar for rbST compared with control. In conclusion, the administration of rbST in lactating dairy cows for 16 d after estrus did not alter the growth of the conceptus collected on Day 17. The greatest responses to rbST were found within the ovary, where rbST increased the weight of the CL and altered the amount of IGF-I and IGFBP in the follicular fluid.

The interactions between the maternal uterus and the developing conceptus that underlie normal blastocyst development and successful progression of pregnancy are complex. Recent studies implicate peptide growth factors in the initiation, establishment and maintenance of pregnancy and in maternal-embryonic communication. The insulin-like family of growth factors appear to function as key mediators of the coordinate development of the uterus and conceptus during early pregnancy by virtue of their ability to influence directly or indirectly, the synthesis and secretion of uterine and conceptus secretory proteins. The autocrine and paracrine modes of action of the insulin-like growth factors (IGFs) are modulated within the uterine microenvironment by Type I IGF receptors and IGF binding proteins (IGFBPs), which are themselves subject to local control within the uterus and conceptus, An understanding of the mechanisms by which IGFs regulate and are regulated by, the expression of conceptus signals for maternal recognition of pregnancy may provide novel insights and practical applications towards increasing reproductive efficiency in large animals.

Uterine luminal fluids (ULFs) from Days 10, 12, 14, and 16 cyclic (C) and pregnant (Px) ewes were analyzed for presence of insulin-like growth factors (IGF-I, IGF-II) and other mitogenic factor(s). IGF content and non-IGF mitogenic activity were measured by IGF RIAs after removal of IGF binding proteins and by stimulatory effects on DNA synthesis of density arrested AKR-2B cells, respectively. ULF IGF-I content was not different between days, but differences in IGF-I between C and Px groups at Day 16 (C greater than Px) were found (p less than 0.05). ULF IGF-II content was not different between C and Px ewes; however, differences among days (p less than 0.01) were apparent. In both C and Px ewes, Day 14 ULF had highest IGF-II content (C: 4.60 +/- 0.98 ng/ml, Px: 5.39 +/- 1.38 ng/ml). In Day 12 and Day 14 (C and Px) ULF, IGF-II concentration was about 10-fold greater than that of IGF-I. AKR-2B mitogenic activity in ULF differed among days (p less than 0.01), but not between C and Px ewes. Highest activity was observed for Day 14 and Px ULF, whereas lowest activity was for Day 10 C and Day 16 Px ULF. Sephadex G-200 gel-filtration chromatography of ULF from Day 14 Px ewes demonstrated mitogenic activity in the column void volume fractions and in the 30-kDa size range of eluted proteins. Day 13 conceptuses were cultured in serum-free medium to define the effect of exogenous IGFs on ovine trophoblast protein-1 (oTP-1) secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Uterine luminal fluids (ULF) from Large White (LW) and prolific Chinese Meishan (MS) gilts were compared with respect to their peptide growth factor content during an estrous cycle and early pregnancy. Insulin-like growth factor-I (IGF-I) was quantitated by RIA; in vitro growth promoting properties of uterine luminal fluid mitogen (ULFM) were measured by [3H]thymidine incorporation into DNA of quiescent AKR-2B fibroblastic cells in culture. Peak concentrations (pg/microgram ULF protein) of IGF-I in ULF of Large White and Meishan gilts, respectively, were: estrous cycle, 9.8 +/- 1.4 (on d 10) and 39.7 +/- 7.8 (on d 12); gestation, 13.1 +/- 3.2 (on d 8 and 10) and 11.9 +/- 2.1 (on d 12), with differences among days (except d 10, P greater than .5) being affected by breed (P less than .10). For both breeds, there was a rapid decline in IGF-I concentrations by d 14 of the cycle and of pregnancy. Uterine luminal fluid mitogen activity was greater (P less than .01) for LW than for MS gilts on d 10 to 14 of an estrous cycle and gestation and diminished in a time-dependent manner in both breeds. No correlation was observed between IGF-I concentrations and uterine weights for either breed. In contrast, a negative correlation between uterine weight and ULFM activity was detected for cyclic (MS: r = -.855, P less than .10; LW: r = -.834, P less than .05) and pregnant (MS: r = -.806, P less than .10; LW: r = -.928, P less than .05) gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Uterine luminal fluids (ULF) from early (Days 10 and 12)-pregnant sows contain factors that stimulate DNA synthesis in a variety of cell lines. The major growth factor component in these fluids has been partially purified 200-fold by heat treatment, anion-exchange chromatography, and gel filtration using mouse embryo-derived AKR-2B fibroblasts as an indicator cell line. The ULF mitogen (ULFM) is a polypeptide with an apparent molecular weight of 4800; it is extremely heat stable and resistant to treatment with urea. This mitogen is also present in ULF from cycling sows but is not detectable in uterine cytosolic extracts or in serum isolated from pigs at Day 12 of pregnancy. The addition of this factor to medium containing 0.5% calf serum results in a 50% increase in final cell density of AKR-2B cells. ULFM appears biologically distinct from mouse and human epidermal growth factor (EGF), since its activity is not inhibited by antibody to mouse EGF and it does not compete for binding to human (A431) EGF receptors. In addition, the ULF factor stimulates DNA synthesis in human A431 epidermoid carcinoma cells, whereas EGF is inhibitory. Partially purified ULFM also stimulates DNA synthesis in primary cultures of pig uterine stromal cells. This mitogen activity is dose-dependent and is not inhibited by antibody to mouse EGF. Thus ULFM may act in concert with other peptide growth factors in regulating uterine growth and/or differentiation.

Cryopreservation of mammalian eggs has been successfully accomplished using 1,2-propanediol (PG). Effects of holding times of 0 and 30 min at −40° C and storage times of 1 d and 1 mo at −196° C were investigated in combination with various concentrations of PG (1.0, 1.5, and 2.0M) to determine the survival and fertilizability of mouse oocytes rapidly frozen and thawed in straws. A rapid one-step dilution using 0.5 M sucrose solution inside the straws was used following the thawing of oocytes.