Accurate determination of in vivo oocyte maturation is particularly critical for dog cloning compared to other assisted reproductive technologies because oocytes in metaphase II stage have to be recovered in order to undergo somatic cell nuclear transfer right after its recovery. The aim of present study was to evaluate the reliability and to set a reference range of a chemiluminescence enzyme immunoassay (CLEIA) compared to radioimmunoassay (RIA) method to retrieve in vivo matured oocytes. Serum progesterone concentration during proestrus and estrus was analyzed by RIA and CLEIA to determine ovulation day (Day 0). On Day 3, in vivo oocytes were recovered surgically and evaluated microscopically maturation status after staining nucleus with bisbenzimidazole dye. Mean progesterone concentration by CLEIA ($7.64{pm}0.06ng/ml$) was significantly higher than by RIA ($6.46{pm}0.04ng/ml$, P < 0.0001). It was not different between CLEIA ($10.01{pm}0.34ng/ml$) and RIA values ($7.91{pm}0.14ng/ml$, P < 0.05) on Day 0, but significantly higher CLEIA level on Day -1 and Day 1 ($6.41{pm}0.15$ and $14.25{pm}0.44ng/ml$) was assessed compared to RIA ($4.95{pm}0.10$ and $11.29{pm}0.34ng/ml$). However, with both methods, progesterone level was significantly increased from Day -1 to Day 2. To determine oocyte maturation with CLEIA method, a wider and higher reference range has to be considered.

Keywords: chemiluminescence enzyme immunoassay, in vivo matured oocyte, progesterone, dog.