Identification and content of insulin-like growth factors in porcine oviductal fluid.

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 < 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 I. Whereas IGF content differed between estrus and nonestrus periods, IGF concentrations were similar (p > 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. Plasma concentrations of IGF-I and IGF-II ranged from 40 to 100 ng/ml and 100 to 400 ng/ml, respectively, during the cycle. Concentrations of both IGFs in the blood plasma were similar (p > 0.05) between the peri-estrus and nonestrus periods when compared by overall means or within each animal. Thus, plasma concentrations did not vary over time in the same way as the contents or concentrations of IGF in the OvF. Plasma E2 was highest at estrus in all animals, coinciding with highest OvF flow and content of both IGFs. Oviductal epithelial cells collected on Day 2 of the cycle were cultured and found to secrete IGF-I and IGF-II into the media. It is concluded that OvF contains IGF-I and IGF-II in significant quantities and that the oviduct can and does produce both IGFs throughout the estrous cycle, this activity being greatest at peri-estrus.