Localization and timing of appearance of insulin, insulin-like growth factor-I, and their receptors in the human fetal müllerian tract.

Objective: The factors that regulate fetal müllerian tract development are still unknown. Insulin and insulin-like growth factor-I are peptides postulated to serve as autocrine or paracrine regulators of cell activity. We have previously demonstrated that messenger ribonucleic acid for insulin and insulin-like growth factor-I receptors are expressed in fetal uterine tissues. We undertook this study to determine by immunohistochemical techniques the exact location of these two growth factors and their receptors in the human fetal uterus.

Study Design: We obtained freshly discarded human fetal uteri (n = 12) between 15 and 22 weeks of gestation from elective pregnancy terminations. Frozen-section specimens were incubated with antibodies against insulin, insulin-like growth factor-I, insulin receptor, and insulin-like growth factor-I receptor. These sections were then incubated with a second antibody conjugated to fluorescein isothiocyanate and examined under phase and fluorescent microscopy.

Results: The fetal endometrium at 19 and 22 weeks of gestation contained insulin, insulin-like growth factor-I, insulin receptor, and insulin-like growth factor-I receptor. The distribution of immunofluorescence in the endometrium is similar for both insulin and its receptor. The same pattern of immunostaining was likewise demonstrated for insulin-like growth factor-I and its receptor.

Conclusion: The localization of these growth factors and their receptors, combined with our previous messenger ribonucleic acid data, suggest an autocrine or paracrine role for insulin and insulin-like growth factor-I in the developing human fetal müllerian tract.