Identification and Content of Insulin-like Growth Factors in Porcine Oviductal Fluid1

Abstract

Oviductal fluid (OvF) was collected from gilts by indwelling catheters during the estrous cycle and analyzed for content of insulin-like growth factors (IGF-I, IGF-II). Group 1, composed of 9 gilts in a summer environment near a boar, yielded mean daily fluid volumes of 1.18 +/- 0.16 ml during estrus and 0.69 +/- 0.03 ml post-estrus. Group 2, composed of 7 gilts in a moderate-temperature, light-regulated room, yielded 1.20 +/- 0.18 ml during estrus and then OvF flow essentially stopped. Serum samples were also collected 2 times daily during the cycle and analyzed along with the OvF for IGF-I and IGF-II. Serum was also analyzed for estradiol-17 beta (E2). For group 1, OvF content (concentration x fluid volume) of IGF-I and IGF-II was greater (p less than 0.05) at estrus than pre- and post-estrus. Daily mean content values (ng/day) for IGF-I and IGF-II during peri-estrus were 30.9 +/- 6.3 and 62.2 +/- 12.3, respectively. During nonestrus, values were 6.8 +/- 6.3 and 11.7 +/- 12.3, respectively. For group 2, OvF content of IGF-I and IGF-II during estrus was similar to that of group 1. Whereas IGF content differed between estrus and nonestrus periods, IGF concentrations were similar (p greater than 0.05), a finding that results from the difference in OvF produced. Compared with OvF concentrations of IGF for a given pig, blood plasma concentrations of IGF-I and IGF-II were 2- to 5-fold higher in the plasma sample collected the same day.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of IGF-I and porcine oviductal secretory protein (pOSP) secretion into the pig oviduct in the peri-ovulatory period, and effects of previous nutrition

“…An explanation for the differences in plasma IGF-I concentration observed 12 to 24 h after ovulation could be that nutritionally-induced changes in folliculogenesis, although not evident in the period of follicular recruitment [3], could be further augmented during the later stages of preovulatory follicular growth. However, it is unlikely that differences in ovarian IGF-I could contribute to the differences found in this study, since previous studies have been unable to link serum IGF-I concentrations to the estrous cycle [29]. Irrespective of gilt or treatment in Experiment 3, IGF-I concentrations in oviduct plasma and oviduct flushings were related.…”

“…Although previous studies have characterized IGF-I concentrations [29] and pOSP protein and mRNA abundance [11] during the estrous cycle, neither reported changes during the critical periovulatory period. Furthermore, because we have shown that the interval between the onset of estrus and the time of ovulation is highly variable in gilts, we believed it was critical to use the moment of ovulation as a critical reference point in these studies.…”

“…concentrations have been associated with the largest fluid volume in the oviduct during the estrous cycle [29]. Furthermore, de novo protein synthesis and secretion by explanted porcine oviducts was the highest for tissue recovered at estrus and was associated with elevated E 2 concentrations [8].…”

“…We chose pOSPs as biologically relevant markers of the oviduct environment because they are synthesized by the oviduct in response to E 2 [9], and improve blastocyst development in vitro [18]. IGF-I was chosen as another relevant marker because it is present in the highest concentrations in oviduct fluid during estrus in the pig [29], and is reported to increase the proportion of bovine embryos developing to the blastocyst stage in vitro [22].…”

Normal Calves Produced After Transfer of Embryos Cultured in a Chemically Defined Medium Supplemented with Epidermal Growth Factor and Insulin-like Growth Factor I Following Ovum Pick Up and <i>In Vitro</i> Fertilization in Japanese Black Cows

“…In bovine embryos, Prelle et al [42] demonstrated that 100 ng/ml IGF-I significantly increased blastocyst production, while it significantly decreased transcription of IGF-I receptors in the embryo. The IGF-I concentration in oviduct fluid is approximately 61 ng/ml in humans [45] and 24.7-35.3 ng/ml in pigs [46], but that in the bovine has yet to be determined. These findings suggest that a physiologically optimal concentration of IGF-I for bovine embryo development remains to be determined.…”