Biomedical subjects

F Pekonen

Publications and source records attributed to F Pekonen.

At least 37 records · Page 2Linked to original sources

PubMed1992

Intrauterine progestin induces continuous insulin-like growth factor-binding protein-1 production in the human endometrium.

The effect of local intrauterine progestin on endometrial insulin-like growth factor-binding protein-1 (IGFBP-1) production was studied in 60 women using a levonorgestrel-releasing intrauterine device (IUD). Intrauterine progestin was a potent stimulator of stromal cell IGFBP-1 production, with 97% of endometrial specimens showing positive staining by immunohistological methods. After 5 yr or more of intrauterine progestin exposure, 100% (n = 20) of the tissues remained strongly positive for IGFBP-1. The IGFBP-1 content in endometrial tissue homogenates reached values as high as 10 micrograms/mg protein when measured by immunoradiometric assay. In contrast to the continuous endometrial IGFBP-1 production induced by local progestin, no such effect could be found in endometria from subjects with sc progestin-releasing implants or copper IUDs. Although the levonorgestrel-releasing IUD had a striking effect on local endometrial IGFBP-1 production, it had no effect on serum IGFBP-1 levels. By Western ligand blot analysis, the domainating IGF-binding species in endometria exposed to intrauterine progestin was of 28K mol wt, corresponding to IGFBP-1, whereas no IGFBP species of 31-43K, corresponding to IGFBP-2 or IGFBP-3, were detected.

Adult↗

PubMed1991

Human endometrial adenocarcinoma cell lines HEC 1B and KLE secrete insulin-like growth factor binding protein-1 and contain IGF-I receptors.

The production of insulin-like growth factor binding proteins (IGFBP) with special reference to human IGFBP-1 was evaluated in five endometrial adenocarcinoma cell lines (HEC 1A, HEC 1B, KLE, RL952 and AN3CA) in continuous culture. Two of the cell lines (HEC 1B and KLE) produced immunoreactive IGFBP-1. The production was inhibited by clomiphene and progesterone, whereas estrogen, cortisol and insulin had no effect on IGFBP-1 secretion. The two cell lines which secreted immunoreactive IGFBP-1 also had IGF-I receptors, whereas the cell lines RL952 and AN3CA, not producing IGFBP-1, had no saturable IGF membrane binding sites. IGF-I receptor binding to HEC 1B and KLE cells was inhibited in the presence of purified IGFBP-1. In addition to IGFBP-1, the endometrial cancer cells secreted several other forms of IGFBPs as determined by cross-linking. Immunoprecipitation of IGF-BP complexes with a polyclonal antiserum against IGFBP-3 indicated that all cell lines secreted binding proteins antigenically related to IGFBP-3 with molecular weights ranging from 20 to 39 kDa.

Adenocarcinoma↗

PubMed1991

Decidual transformation of human extrauterine mesenchymal cells is associated with the appearance of insulin-like growth factor-binding protein-1.

Human extrauterine decidual cells were studied for the presence of insulin-like growth factor-binding protein-1 (IGFBP-1) by using an avidin-biotin complex immunoperoxidase method with a purified monoclonal antibody 6303 against IGFBP-1. It is well established that human decidua expresses mRNA for IGFBP-1 and synthesizes and secretes this protein. We now describe, for the first time, that cells morphologically similar to uterine decidual cells found beneath the peritoneal mesothelium in inguinal hernia and in the cervical mucosa during normal pregnancy and in the mesenchymal tissue of the Fallopian tubes and ovaries at term react with the monoclonal antibody for IGFBP-1 equally to endometrial decidual cells. These results imply that the extrauterine mesenchymal cells, which have undergone decidual transformation, are not only morphologically but also functionally, similar to their counterparts in the uterus. Secondly, the data suggest that IGFBP-1 expression is associated with a special type(s) of cells and a certain stage of differentiation rather than special organs in the body.

Carrier Proteins↗

PubMed1991

Assays for IGF binding proteins.

Growing interest in IGF binding proteins and their roles in the modulation of IGF actions has prompted several laboratories to establish immunological assays to measure these proteins. Three distinct IGF binding proteins, referred as IGFBP-1, IGFBP-2 and IGFBP-3, have so far had their cDNAs cloned and sequenced. The availability of purified proteins and the development of polyclonal and monoclonal antibodies now allow specific quantitation of different IGFBP classes. This brief review will address on the current progress in the immunological assays of IGFBPs. The importance of the sensitivity, the reproducibility, and the standardization of the assays is discussed. Some additional information, like levels in amniotic fluid and serum of healthy adults and children, is given.

Adult↗

PubMed1990

Plasma androgens and oestradiol during oral glucose tolerance test in patients with polycystic ovaries.

Hyperinsulinaemia is common patients with polycystic ovaries (PCO), and a relationship between hyperinsulinaemia and hyperandrogenaemia has been suggested. We studied the effect of increased circulating insulin in response to an oral glucose tolerance test (OGTT) on plasma levels of androgens and oestradiol in PCO patients and in healthy control subjects. A 75 g, 3 h oral glucose tolerance test (OGTT) was performed in eight non-obese and seven obese PCO patients, and in 10 non-obese control subjects. An additional group of five women were fasting during the study period. The increase in insulin concentration was higher in obese and non-obese PCO patients than in non-obese control subjects, and the peak values were observed at 30 or 60 min. In the fasting control subjects, the mean concentration of androstenedione decreased slightly due to a diurnal variation. During the OGTT, mean concentrations of androstenedione decreased in all groups at 30 min, after which a slight increase was observed in PCO patients and a plateau in control subjects. Similarly, mean testosterone increased after an initial decrease in obese PCO patients whereas no change was found in non-obese PCO patients. No statistically significant differences were found in the responses of androstenedione or testosterone levels to OGTT in obese or non-obese PCO patients compared to normals. No significant responses of plasma oestradiol levels to OGTT were found. These findings failed to demonstrate any significantly abnormal acute androgen responses to OGTT-stimulated hyperinsulinaemia in PCO patients, but did not exclude possible long-term effects of hyperinsulinaemia.

Adult↗

PubMed1990

Insulin-like growth factors and their binding proteins.

Insulin-like growth factors are important multifunctional polypeptides interacting with cell membrane receptors and soluble binding proteins. With expanding knowledge on IGF binding proteins, it is becoming evident that the IGF actions are diverse, and depend on the context set by local binding proteins. In this minireview we attempt to provide a brief summary of the recent development in this field.

Carrier Proteins↗

PubMed1990

Localization of renin substrate in fetoplacental tissue.

Specific polyclonal rabbit anti-human renin substrate-antibodies were used in order to study the distribution of renin substrate immunoreactivity in human fetal and placental tissue. Renin substrate was immunohistochemically detected in human decidua and placenta, as well as in 19 weeks old human fetal liver and kidney. The presence of renin substrate in fetoplacental tissue supports the concept of a locally functioning renin-angiotensin system.

Angiotensinogen↗

PubMed1989

Binding of epidermal growth factor and insulin-like growth-factor I in renal carcinoma and adjacent normal kidney tissue.

The binding of epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) to cell membranes was determined in 14 renal cancers and in 13 normal kidney tissues adjacent to the tumors. The soluble 34K IGF binding protein (34K IGF-BP) content and the phosphotyrosyl-protein phosphatase activity in renal cancer tissue and adjacent normal tissue were also determined. The specific EGF receptor binding in renal cancers was 12.7 +/- 2.5% (mean +/- SEM) as compared to 2.6 +/- 0.2% (mean +/- SEM) in normal tissues (p less than 0.01). Phosphotyrosyl-protein phosphatase activity in renal cancer tissue was less than half of that observed in normal renal tissue (p less than 0.01). The highest IGF-I binding was observed in 5 renal cancers although no consistent differences between IGF-I binding to tumor and normal tissues were observed. Both EGF and IGF binding to kidney tissue were higher than binding to gastro-intestinal tissue irrespective of whether normal or malignant tissues were compared. All normal kidney tissues and 7 of 8 kidney tumors contained measurable amounts of 34K IGF-BP as determined by RIA and the cross-linking technique. In 2 tumor tissue samples the 34K IGF-BP content was increased 8- and 15-fold over that seen in adjacent normal kidney tissue, whereas in the 6 other renal cancers the 34K IGF-BP was similar to that observed in normal kidney tissue.

Adenocarcinoma↗

PubMed1989

Renin substrate in human amniotic fluid.

Purified human amniotic fluid renin substrate (RS) was compared to purified plasma RS. RS in plasma and amniotic fluid were similar in molecular weight, isoelectric point and immunological properties. Immunoreactivity of radio-iodinated amniotic fluid RS was lower than that of plasma RS. Measured by direct radioimmunoassay, RS-levels were only 10-22% of those obtained with indirect assay in 22 amniotic fluid samples. This difference suggests that amniotic fluid RS is less immunoreactive than plasma RS, possibly due to biochemical alteration or complex formation. No such difference in immunoreactivity was noticed in RS of decidual and placental cytosolic fraction.

Amniotic Fluid↗

PubMed1989

Decreased 34K insulin-like growth factor binding protein in polycystic ovarian disease.

Insulin and insulin-like growth factor I (IGF-I) have been implicated in ovarian androgen production. Insulin is closely related to IGF-I and cross-reacts with its receptor. The 34K IGF-binding protein (34K IGF-BP) has been shown to inhibit the binding of IGF-I to its receptor. The authors evaluated the role of insulin in the regulation of serum levels of 34K IGF-BP in patients with polycystic ovarian disease (PCOD). 34K IGF-BP levels during an oral glucose tolerance test (OGTT) were measured in 15 PCOD (8 obese and 7 nonobese) patients and in 10 healthy control subjects. The fasting level of 34K IGF-BP was decreased in nonobese PCOD patients (2.4 +/- 0.3 micrograms/l) (mean +/- standard error) (P = 0.02) and obese PCOD patients (0.59 +/- 0.2 micrograms/l) (P less than 0.001) as compared with healthy controls (4.8 +/- 0.9 micrograms/l). Both nonobese PCOD patients and normal controls demonstrated a significant decrease in 34K IGF-BP following OGTT. An insulin-related decrease in 34K IGF-BP may allow an increased pool of IGF-I able to bind to its receptor. This would provide a mechanism for increased ovarian androgen production via IGF-I stimulation of its receptor.

Adult↗

PubMed1989

A monoclonal antibody-based immunoradiometric assay for low molecular weight insulin-like growth factor binding protein/placental protein 12.

We describe a sensitive immunoradiometric assay for insulin-like growth factor binding protein/Placental Protein12 (IGF-BP/PP12) using monoclonal antibodies. This assay has a detection limit of 0.25 micrograms/l IGF-BP/PP12. Parallel dose response curves were obtained with purified IGF-BP/PP12, amniotic fluid, decidual cytosol extract, and serum. The assay is reproducible (intra-assay variation 4.3-8.2% and interassay variation 9.7-11.1%) and fast (less than 5 hours). A crossreactivity of less than 0.01% for all other proteins tested reflects high specificity. Using this method the mean serum IGF-BP/PP12 concentration in healthy women was 5.2 micrograms/l. During pregnancy, the mean IGF-BP/PP12 at 7-11 weeks was 43.3 micrograms/l, and at 36-40 weeks 121 micrograms/l. After early pregnancy termination the serum IGF-BP/PP12 decreased rapidly reaching a mean level of 8 micrograms/l within 4 days.

Amniotic Fluid↗

PubMed1989

Response of plasma beta-endorphin and insulin to oral glucose tolerance test in non-obese women with polycystic ovaries.

Increased responses of plasma insulin and endorphins to the oral glucose tolerance test (oGTT) have earlier been found in obese women. We studied responses of immunoreactive beta-endorphin (ir beta-E) and insulin in plasma to the oGTT in 8 non-obese women with polycystic ovaries (PCO) and in 10 healthy women. An additional control group consisted of 5 healthy women who were fasting during the study period. In the PCO group the insulin and glucose responses to the oGTT were increased, and an increase of ir beta-E from 5.9 +/- 1.5 to 8.6 +/- 2.8 pmol/l was found during the 1st half-hour period of the oGTT. In contrast, no significant change was found during the oGTT in healthy women (3.2 +/- 0.5 and 2.7 +/- 0.65 pmol/l, respectively), and in the fasting control women the mean ir beta-E level (+/- SE) decreased, from 4.5 +/- 1.2 to 3.6 +/- 1.1 pmol/l. These findings revealed increased responses of both plasma ir beta-E and insulin to the oGTT in non-obese women with PCO but their possible causal relationship remained unsolved.

Adult↗

PubMed1989

Binding of epidermal growth factor and insulin-like growth factor I in human myometrium and leiomyomata.

Samples of uterine myometrium and leiomyoma from 11 women were analyzed for the presence of epidermal growth factor receptors and insulin-like growth factor I receptors. In addition, the content of soluble insulin-like growth factor binding protein (IGF-BP/PP12) was measured in the tissue cytosols. Cell membrane preparations of myoma tissue bound significantly more insulin-like growth factor I than did those of adjacent normal myometrium, whereas myoma tissue bound less epidermal growth factor than did the normal myometrium. The differences in both insulin-like growth factor I and epidermal growth factor binding were due to changes in receptor concentration rather than to alterations in receptor affinity. Neither myoma nor myometrial tissue contained detectable levels of insulin-like growth factor binding protein. The changes in epidermal growth factor and insulin-like growth factor I binding to the myometrium may play a role in the pathogenesis of uterine leiomyomata.

Adult↗

PubMed1988

Monoclonal antibodies to the 27-34K insulin-like growth factor binding protein.

Monoclonal antibodies were prepared against the 27-34K insulin-like growth factor (IGF)-binding protein purified from human placenta/decidua and designated placental protein 12 (PP12). Four different antibodies were characterized. Each recognized the major band at 32K on immunoblots of the purified PP12 preparation and amniotic fluid. In liquid phase RIA, IGF-I did not affect the binding of [125I] PP12 to one antibody (Mab 6303), it slightly increased the binding to two antibodies (Mab 6301 and 6304), and it slightly decreased the binding to one antibody (Mab 6302). All antibodies immunoprecipitated the cross-linked PP12-[125I] IGF-I complex, but Mab 6302 considerably less effectively than the others. Preincubation of PP12 with Mab 6302 completely inhibited the binding of [125I] IGF-I to PP12, whereas preincubation with Mab 6303 had no effect, and Mab 6301 as well as Mab 6304 increased it. These results suggest that Mab 6302 binds to an epitope at or near to the IGF-binding site, whereas the other antibodies react at other sites of the PP12 molecule. Conformational changes in PP12 probably account for the IGF-I-induced increase in the binding of Mabs 6301 and 6304 to [125I] PP12, and vice versa, for Mabs 6301- and 6304-induced increase in the binding of [125I] IGF-I to PP12.

Antibodies, Monoclonal↗

PubMed1988

Receptors for epidermal growth factor and insulin-like growth factor I and their relation to steroid receptors in human breast cancer.

Levels of epidermal growth factor receptor (EGF-R) and insulin-like growth factor receptor (IGF-R) in breast cancer tissue were evaluated. The binding of growth factors was compared to the content of estrogen receptors (ER) and progesterone receptors (PgR). EGF-R correlated negatively to the ER and PgR (Kendall correlation, P less than 0.001), whereas the IGF-R correlated positively to ER and PgR (analysis of variance, P less than 0.001). In contrast, no correlation was found between EGF-R and IGF-R. IGF-R binding was higher in tumor tissues than in adjacent normal tissues (Wilcoxon rank test, P less than 0.001), whereas the EGF-R binding in normal tissue did not differ from that in cancer tissue. The degree of differentiation in ductal breast cancer correlated to EGF-R (chi 2 test, P = 0.018), but not to IGF-R. The bindings of both growth factors were the same in metastases and primary breast tumors. Our results show that EGF-R and IGF-R are present in normal breast tissue and breast cancer tissue. The growth factor receptors are related to steroid receptor content and their presence is associated with malignant transformation of breast cells and dedifferentiation of breast cancer.

Adult↗

PubMed1988

Characterization of functional type I insulin-like growth factor receptors from human choriocarcinoma cells.

Specific receptors for insulin-like growth factor I (IGF-I) on cultured human choriocarcinoma cells (JEG-3 and BeWo) were characterized. The binding of 125I-labeled recombinant (Thr59)IGF-I to the cells was reversible and time, temperature, and pH dependent. Steady state of binding occurred after 16 h at 4 C, pH 7.4. Natural human IGF-I (hIGF-I), hIGF-II, recombinant (N-Met)IGF-I, rat multiplication-stimulating activity, and insulin were 200%, 37%, 37%, 1.6%, and 0.1% as potent as (Thr59)IGF-I in inhibiting the binding of [125I]iodo-(Thr59)IGF-I to JEG-3 cells, respectively. Epidermal growth factor was ineffective. The half-maximal displacement of [125I]iodo-(Thr59)IGF-I by unlabeled (Thr59)IGF-I occurred at 11 +/- 2 ng/ml (mean +/- SEM) in both JEG-3 and BeWo cells. Scatchard analysis of the competitive binding data revealed linear plots indicating a single species of binding sites with an association constant of 0.8 X 10(9) M-1 for the binding of [125I]iodo-(Thr59)IGF-I to both cell lines. The binding capacity was 30,000 and 20,000 sites/cell for JEG-3 and BeWo cells, respectively. Chemical cross-linking of [125I]iodo-(Thr59)IGF-I to JEG-3 cells revealed two receptor complexes of 130K and 260K. Their formation was completely inhibited by an excess of unlabeled (Thr59)IGF-I or hIGF-II. Increasing amounts of insulin affected both labeled bands equally, suggesting that the 130K and 260K bands represent the monomer and dimer forms, respectively, of the ligand-binding alpha-subunit of type I IGF receptor. (Thr59)IGF-I, in a dose-dependent manner, stimulated uptake of nonmetabolizable alpha-[3H]aminoisobutyric acid by JEG-3 cells, showing that the receptor is biologically active. Our results demonstrate that choriocarcinoma cells possess functional high affinity type I IGF receptors and suggest that IGF-I is involved in the growth-regulating processes of JEG-3 and BeWo cells. These cells may provide a useful model to study the role of IGFs in trophoblast physiology.

Aminoisobutyric Acids↗

PubMed1988

Epidermal growth factor but not insulin-like growth factor-I potentiates adenosine 3',5'-monophosphate-mediated chorionic gonadotropin secretion by cultured human choriocarcinoma cells.

Epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) regulate hormone production in several endocrine cells cultures. We have previously found that 12-O-tetradecanoyl phorbol-13-acetate (TPA), a protein kinase C activator, potentiates the cAMP-mediated secretion of human CB (hCG) in cultured human choriocarcinoma cells. We have now studied whether EGF and IGF-I modify cAMP-mediated hCG secretion in JEG-3 cells, which possess high affinity receptors to these growth factors. EGF, TPA, and cholera toxin (CT), an activator of adenylate cyclase, stimulated the secretion of hCG in a concentration-dependent manner during a 24-h culture period. The maximal effective concentrations of EGF (10 ng/ml), TPA (10 ng/ml), and CT (1.0 ng/ml) exerted 2.3-, 2.4-, and 3.9-fold increase over unstimulated level, respectively. EGF and TPA potentiated the effect of CT on hCG secretion from 3.9- to 7.8-fold and from 3.9- to 14.8-fold, respectively. By contrast, IGF-I was ineffective. During a 24-h culture, EGF and TPA potentiated the effect of CT on cAMP accumulation 1.4-fold and 1.3-fold over the production of CT-treated cells. Time-course studies indicated that these effects on cAMP and hCG were detectable at 3 h and 6 h, and they continued to increase up to 48 h and 72 h, respectively. When added alone, EGF and TPA increased cAMP production y 2.0-fold and 2.5-fold over controls at 24 h. Again, IGF-I was ineffective. Moreover, EGF and TPA potentiated the effect of 8-bromo-cAMP (on hCG production to a similar extent than they did to CT-stimulated hCG production. The binding of [125I]iodo-EGF to the cells was not altered by a 48-h CT-treatment whereas the binding of [125I]iodo-IGF-I was increased by 2.1-fold above untreated cells. Our data show that both EGF and TPA potentiated the effect of CT on hCG secretion in JEG-3 cells, whereas IGF-I had no effect. Although EGF and TPA facilitated CT-stimulated cAMP accumulation, their site of action on cAMP-mediated hCG production is distinct from the adenylate cyclase or EGF-receptor level since EGF and TPA potentiated the hCG secretion stimulated by 8-bromo-cAMP and an increase in cAMP production did not alter the binding properties of EGF-receptor.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1988

Soluble 34K binding protein inhibits the binding of insulin-like growth factor I to its cell receptors in human secretory phase endometrium: evidence for autocrine/paracrine regulation of growth factor action.

The human secretory phase endometrium synthesizes and secrets a 34K insulin-like growth factor (IGF)-binding protein designated placental protein 12. We now report that membrane preparations of human endometrium possess IGF receptors that complete with the soluble binding protein for binding to IGF-I. Multiplication-stimulating activity and insulin were 1% and 0.1% as potent as recombinant (Thr59)IGF-I in inhibiting the binding of [125I](Thr59)IGF-I to endometrial membranes. Scatchard plots for the IGF-I binding data were curvilinear, and the apparent affinities [Ka = 1.4 +/- 0.2 ( +/- SEM) X 10(9) M-1] for (Thr59)IGF-I (high affinity site) did not change during the menstrual cycle. Affinity cross-linking of [125I](Thr59)IGF-I to endometrial membranes revealed two major bands with mol wt of 130K and 260K on sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. The 130K band is consistent with the alpha-subunit of the type I IGF receptor. The 260K band is either the type II IGF receptor or represents cross-linking (dimer) of two alpha-subunits of the type I receptor. A less intense band at about 40K was also seen in all membrane preparations. It comigrated with the cross-linked purified 34K binding protein. The band was more intensely labeled when the tracer was cross-linked to proteins in the cytosol fractions of late secretory phase endometria. By specific RIA, the 34K binding protein was detected in the cytosol of late secretory phase endometria only. Newly synthesized binding protein, which contaminated membrane preparations, caused an apparent increase in the binding of (Thr59)IGF-I to the membranes prepared from late secretory phase endometria when studied by competitive binding assay. In contrast, purified binding protein prevented the binding of [125I](Thr59)IGF-I to membrane receptors, as confirmed by affinity cross-linking. These results suggest that the 34K IGF-binding protein, secreted by the human endometrium in a cyclic fashion, has a significant role in inhibiting the receptor binding and, thus, the possible biological action of IGF-I in the endometrium in an autocrine/paracrine manner.

Binding, Competitive↗