Differential growth factor content of uterine luminal fluids from large white and prolific Meishan pigs during the estrous cycle and early pregnancy.

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)