The influence of insulin on secretion of IGF-I and IGFBP-I in cultures of human endometrial stromal cells.

Objectives: To study the influence of insulin on IGF-I and IGFBP-I secretion of the human endometrial stromal cells.

Methods: Late proliferative phase endometrial stromal cells were isolated from endometrium tissues and then cultured for 24 h in Hams F-12 only as a control and in Hams F-12 with different concentrations of estradiol (E2) and insulin (INS) as treated groups. Simultaneously, the endometrial stromal cells from late secretory phase endometrium were cultured for 24 h in Hams F-12 only as a control and in Hams F-12 supplemented with different concentrations of progesterone (P) and insulin as treated groups. After 24 h of culturing, the mediums were collected for either IGF-I or IGFBP-I assays.

Result: The concentrations of IGF-I in medium from cultured endometrial stromal cells in the proliferative phase were 0.78 +/- 0.47 ng/ml in the hormone-free control group; 1.44 +/- 0.59 ng/ml and 1.39 +/- 0.33 ng/ml in 100 pg/ml E2 group and 20 microU/ml INS group, which was higher than that of the control group (P < 0.05 and P < 0.01, respectively). The IGF-I concentration in the 100 microU/ml INS group was 2.03 +/- 0.53 ng/ml, which was higher than that of the 20 micro U/ml INS group (P < 0.01). Levels of IGF-I in the 100 pg/ml E2 plus 20 microU/ml INS group was 2.18 +/- 0.36 ng/ml, which was significantly higher than that of the 20 microU/ml INS and 100 pg/ml E2 group (P < 0.01), but lower than that of the 100 pg/ml E2 plus 100 microU/ml INS group (3.42 +/- 0.75 ng/ml), P < 0.01. The concentration of IGFBP-I in medium from cultured endometrial stromal cells in the secretory phase was 2.50 +/- 1.39 ng/ml in the hormone-free control group and 5.44 +/- 2.09 ng/ml in the 10 pg/ml P group, which was significantly higher than that of the control (P < 0.01). IGFBP-I concentration in 20 microU/ml INS group was 0.16 +/- 0.58 ng/ml, which was lower compared with control, but higher compared with the 100 microU/ml INS group (P < 0.01). The level of IGFBP-I in the 10 ng/ml P plus 20 microU/ml INS group was 2.10 +/- 1.17 ng/ml, lower compared with the 10 ng/ml P group, but higher compared with the 10 pg/ml P plus 100 microU/ml INS group, P < 0.01.

Conclusions: Insulin can stimulate basal (without hormone) and E2-stimulated IGF-I secretion in cultured stromal cells from human late proliferative endometrium in a dose-dependent manner. Insulin can suppress basal (without hormone) and P-stimulated IGFBP-I secretions in cultured stromal cells from human secretory endometrium in a dose-dependent manner.