Comparison of three methods for investigating placental protein 12(PP12)-like immunoreactive substance from preovulatory follicular fluid and purified PP12 from human placenta

Relationship between follicular fluid levels of insulin-like growth factor binding protein-1 and sex steroids from normal human ovarian follicles

The aim of this study was to examine the possible correlations between follicular fluid insulin-like growth factor binding protein 1 (IGFBP-1) and follicular fluid and serum parameters of granulosa cell function. Twenty-six subjects undergoing diagnostic laparoscopy for infertility had follicular fluid samples collected. Subjects were aged 20-42 years, were having regular ovulatory cycles and either had tubal disease or a partner with male factor infertility. Sex steroids, insulin-like growth factor 1 (IGF-1) and IGFBP-1 were measured by radioimmunoassay. Follicular fluid levels of IGFBP-1 were significantly correlated with levels of estradiol, progesterone in follicular fluid and with serum IGFBP-1 levels, and negatively correlated with follicular fluid androstenedione levels. These results suggests that IGFBP-1 may have a role in the regulation of human ovarian follicles.

Insulin-like growth factor binding proteins in follicular fluid from normal dominant and cohort follicles, polycystic and multicystic ovaries

There is now considerable evidence that the insulin-like growth factors (IGFs) play an important role in the human ovary. It has also recently become apparent that the physiological activity of the IGFs is modulated by a number of specific binding proteins (IGFBPs). In order to understand the role of the IGFs in ovarian physiology, the presence and functions of these IGFBPs will need to be characterized. As an initial step towards this we have investigated the presence of the various binding proteins by Western ligand blotting and have measured the levels of one of them, IGFBP-1, in follicular fluid (FF) obtained from unstimulated dominant and cohort follicles in 19 normal women and in eight patients with polycystic and one with multicystic ovaries. In normal women, IGFBP-1 levels in dominant follicles were similar to matched serum levels but were significantly lower in cohort follicles. IGFBP-1 levels correlated with FF-volume (r = 0.58, P less than 0.001) and with paired serum levels (r = 0.63, P less than 0.001). In post-LH surge dominant follicles this relationship with serum levels no longer held and in three out of nine subjects FF levels were higher than in serum. Thus IGFBP-1 in normal human FF appears to be partly derived from the circulation but with additional local production in the larger developing dominant follicles. Western ligand blotting revealed five IGF-binding proteins in FF running parallel with those identified in serum, suggesting that the IGFBP species previously identified in serum may also be present in FF. The two bands in positions corresponding to the components of the large (150kDa) binding complex were, as in serum, the predominant forms and in most FF samples these were even more prominent than in the accompanying serum sample. This contrasts with previous studies in lymph which suggested that the 150kDa complex was largely retained in the circulation. All three small IGFBPs varied considerably between FF samples even within an individual; each IGFBP varied independently of the other IGFBPs. Our results demonstrate that at least four discrete IGFBPs are present in FF and suggest that each may be produced independently within the ovary.

Human granulosa cells contain insulin-like growth factor-binding protein (IGF BP-1) mRNA

Previous studies have demonstrated expression of insulin-like growth factor-binding protein (IGF BP-1) in secretory and decidualized endometrium, in adult and fetal liver, and in HepG2 liver cancer cells. We have studied the expression of IGF BP-1 in various types of ovarian neoplasias, normal ovary, and granulosa cells from hyperstimulated human ovarian follicles by RNA blot hybridization. A single 1.6 kb mRNA species, similar to that present in human decidua, was identified in poly(A)RNA-containing preparations of granulosa cells and of a borderline malignant ovarian cystadenoma. This finding verifies the postulated production of IGF BP-1 by the human ovary.

Elevated levels of a somatomedin-binding protein PP12 in patients with ovarian cancer

The circulating levels of placental protein 12 (PP12), a somatomedin-binding protein, were measured by radioimmunoassay in 37 postmenopausal women with ovarian tumors. Elevated levels (above 47 micrograms/l) were observed in 16 of 25 patients (64%) with malignant and 2 of 12 patients (17%) with benign tumors. Elevated levels were more frequent and higher in patients with advanced disease. Within 1 week of surgery, the levels fell in 13 of 17 cases (77%). In addition to clinical interest, these results contribute to our knowledge of carrier proteins of growth factors in patients bearing malignant ovarian neoplasms.

New placental proteins: chemistry, physiology and clinical use

In the past decade, several new placental proteins have been isolated and studied. The 'pregnancy-specific' beta 1-glycoprotein (SP1) is a major placental product with unusual physicochemical properties that has been extensively investigated, but its biological function remains uncertain. Pregnancy-associated plasma protein A (PAPP-A), a glycoprotein of mol. wt 400,000, has effects in vitro on the coagulation and complement cascades, probably by its properties of protease inhibition. Placental protein 5 (PP5) may be involved in the coagulation and fibrinolytic systems, and in follicle maturation and semen liquefaction. 'Placental protein 12' (PP12) is not a product of the placenta at all; it appears to be produced in the female genital tract under the influence of progesterone and may also be produced by proliferating liver cells. Further study may reveal new roles for these placental proteins beyond their traditional roles as tumour markers.