Concentrations of energy substrates in oviductal fluid and blood plasma of pigs during the peri-ovulatory period

Abstract

Large White gilts, 9 to 18 months old, that had exhibited at least two natural oestrous cycles were divided into three groups (phases): unmated pre-ovulatory, unmated post-ovulatory and mated post-ovulatory (n= 16, 20 and 18). Oviductal luminal fluid samples were collected under anaesthesia by micropipette from the ampulla and ampullary-isthmic junction and analysed by an ultramicrofluorometric technique. Glucose concentrations (mmol l-1, means combining regions; mean ± SEM) were significantly higher in blood plasma than in oviductal fluid (4.56 ± 0.20 versus 0.59 ± 0.16; P < 0.0001; n = 27), whereas lactate was higher in the oviduct (5.71 ± 0.53 versus 2.48 ± 0.24; P < 0.0001; n = 27). No significant differences were found between the ampulla and the ampullary-isthmic junction. However, the concentration of glucose was significantly higher (P < 0.05) in the ampulla of the pre-ovulatory group (0.97 ± 0.20; n = 13) compared with the mated group (0.25 ± 0.05; n = 14) and its concentration in the ampullary-isthmic junction in the pre-ovulatory group (1.65 ± 0.63; n = 13) was significantly greater (P < 0.05) than in the post-ovulatory (0.43 ± 0.11; n = 11) or mated groups (0.17 ± 0 02; n = 14). Lactate in the ampulla of mated animals was higher than in the pre-ovulatory group (6.83 ± 0.70 versus 3.86 ± 0.38; P < 0.05; n = 15 and 13), but neither was significantly different from the post-ovulatory group. Furthermore, no change was seen at the ampullary-isthmic junction in lactate concentration with phase. Pyruvate concentrations showed no differences with phase, region or with plasma (oviduct 0.21 ± 0.02; plasma 0.14 ± 0.01; n = 27 and 26). Glucose concentration within the oviduct decreased at a time when gametes or embryos, with their liberated cumulus cells, were present. Consequently it is evident that the microenvironment of the gametes and embryos is changing and, in the light of these measurements, the composition of the media used for in vitro culture experiments may require modification to reflect the physiological levels more closely.