Comparison of trophic effects of norepinephrine, insulin, and IGF-1 in mouse brown adipocytes.

The objective of this work was to evaluate whether insulin, like norepinephrine (NE), exerts direct growth effects in brown adipocytes, as assessed by changes in rates of protein labeling with [35S]methionine. Mouse brown adipocytes isolated by tissue collagenase digestion were incubated for up to 24 h with or without NE in Dulbecco's modified Eagle's medium with albumin, calf serum, and antibiotics. There was a 40% cell loss and a 50% decrease in cell content of succinate dehydrogenase (SDH) activity over 24 h. Both cell recovery and SDH content significantly improved in the presence of NE. In addition, NE increased [35S]methionine incorporation into proteins in both cytosolic and mitochondrial compartments. These effects of NE were inhibited by propranolol. Both insulin and insulin-like growth factor-1 (IGF-1) receptors were detected in brown adipocytes, with insulin receptors in much greater concentration. Increased protein labeling was observed when brown adipocytes were incubated for 4 h with 0.2-5 nM insulin in the absence of serum. This effect was small (30% stimulation) compared with the 200-350% increase observed with NE, and 5 nM IGF-1 had no effect. These results indicate direct trophic actions of both NE and insulin in mouse brown adipocytes, with the effects of NE an order of magnitude greater than those of insulin.

Serum insulin, IGF-I,IGF-II and growth hormone, and left ventricular mass in noninsulin-dependent mellitus.

OBJECTIVE: To investigate whether serum insulin, insulin-like-growth factor I (IGF-I),insulin-like-growth factor II (IGF-II) and growth hormone (GH)--each of which is a known trophic factor in vitro for the cardiomyocyte, and levels of which can be altered in noninsulin-dependent diabetes mellitus (NIDDM)--related of left ventricular (LV) mass in patients with NIDDM. DESIGN: Observational study. SETTING: University teaching hospital. PATIENTS AND METHODS: Patients with NIDDM without signs, symptoms or past history of hypertension, ischemic or valvular heart disease, or heart failure were recruited from the diabetes clinic of an university hospital. Fasting patients had blood drawn for determination of serum insulin, IGF-I, IGF-II and GH by radioimmunoassay. Height, weight, and blood pressure were recorded. An electrocardiogram was obtained and echocardiography were performed for calculation of LV mass. RESULTS: Patients' average age was 54.7 +/-1.6 years, and duration of NIDDM was 9.3 +/- 1.2 years. LV mass was 113.7 +/- 8.9 g/m2 in men (n=13) and 104.1 +/- 10.8 g/m2 in women (n=10). Serum insulin was 25.3 +/- ng/mL, IGF-I was 255 +/- 15 ng/mL, IGF-II was 0.62 +/- 0.05 microg/mL and GH was 5.4 +/- 0.5 ng/mL. There were no significant differences in LV mass among patients with serum insulin, IGF-I, IGF-II or GH in the upper compared with the lower 50th percentile. There were no significant differences in serum insulin, IGF-I, IGF-II or GH among patients in the upper compared with the lower 50th percentile for LV mass. Standardization of LV mass for body size, either by height or body surface area, did not alter the relationships. The correlation coefficients from linear least squares regression analysis between these hormones and LV mass were low (r<0.003), suggesting that even much larger sample sizes might not alter these findings. CONCLUSIONS: These data suggest that circulating total serum concentrations of growth factor (insulin, IGF-I, IGF-II and GH) are not determinants of LV mass in nonhypertensive patients with NIDDM.

Differential binding and internalization of insulin-like growth factor (IGF)-I in cultured human trophoblast and JEG-3 cells: possible modulatory effect of IGF binding proteins (BP).

The present study was undertaken to characterize and identify the insulin-like growth factor binding proteins (IGF BPs) secreted by placental cells and their possible modulatory effect on IGF-I binding to cell surface receptors. The experimental approach taken was comparative characterization of binding and internalization of IGF-I and its analog, [Gln(3), Ala(4), Tyr(15), Leu(16) (QAYL)]IGF-I, with reduced affinity for IGF BP, in two different placental cell culture models. One was human placental trophoblast in primary culture and the other, JEG-3 cells, a human choriocarcinoma cell line, representing placental trophoblasts. Binding of [(125)I]IGF-I in both trophoblast and JEG-3 cells was time and temperature dependent. At 37°C, the plateau of [(125)I]IGF-I binding to both the cells (1-2% specific binding per 10(5) cells) was reached by 40-60 min. At 4°C, the time required to reach the plateau in both cells was increased to ∼4h. The maximum binding of [(125)I]IGF-I to trophoblasts, however, was ∼2 times higher than at 37°C, whereas in JEG-3 cells binding remained the same. Internalization of [(125)I]IGF-I in trophoblast cells was low and temperature independent. At both 37 and 4°C, ≤30% of the total cell-associated [(125)I]IGF-I was internalized. In contrast, internalization of [(125)I]IGF-I in JEG-3 cells was rapid and temperature dependent. At 37°C, ≥60% of the total cell-associated [(125)]IGF-I was internalized by 40-60min. At 4°C, internalization was slow and did not exceed 10% of the total cell-associated radioactivity. Binding of [(125)I-QAYL]IGF-I to trophoblasts, in comparison to [(125)I]IGF-I, was significantly different. The binding was undetectable at 37°C and it was low at 4°C. In JEG-3 cells, however, the binding and internalization of [(125)I]-QAYL]IGF-I at both the temperatures were comparable to that of [(125)I]IGF-I. Further characterization of the two [(125)I]IGF-I bindings to the different placental cells was achieved by binding competition studies using unlabelled IGF-I, [QAYL]IGF-I and [Leu]IGF-I, another analog of IGF-I, [Leu(24), 1-62]IGF-I with reduced affinity for the IGF-I receptor, and α-IR3, a monoclonal antibody to the IGF-I receptor. The different potencies of IGF-I and its analogs, and α-IR3 in competing binding of two [(125)I]IGF-Is in the different cells suggested that binding of IGF-I to JEG-3 cells was predominantly to IGF-I receptor, whereas to trophoblast cells it was to IGF BP. This was confirmed by affinity cross-linking studies. The major affinity cross-linked [(125)I]IGF-I complex in trophoblast cells was shown to be a protein of Mr. ∼43 kDa, corresponding to IGF BP-3. In JEG-3 cells, the major cross-linked [(125)I]IGF-I and-[QAYL]IGF-I complexes were proteins of Mr ∼130 kDa and >260 kDa, corresponding to the monomeric and multimeric forms of IGF-I receptor. The ∼43 kDa complex in trophoblast was confirmed to be IGF BP-3 by identification of the characteristics of the IGF BP secreted by trophoblast by Western ligand and immunoblots of the conditioned media. JEG-3 cells did not secrete IGF BP. In conclusion, the membrane associated IGF BP-3 in trophoblast cells, shown here, imply anin vivo modulatory effect of membrane bound IGF BP-3 on IGF-I action in placenta. JEG-3 cells, not secreting IGF-BP, offer an attractive model to study the interactive mechanism of IGF-I and IGF BP-3 actions on the placenta.

Insulin-like growth factor (IGF) binding proteins and insulin-like growth factor secretion by cultured chondrocyte cells: identification, characterization and ontogeny during cell differentiation.

Insulin-like growth factor binding proteins (IGF BP) and insulin-like growth factors (IGF) secretion by differentiating chondrocytes, derived from mouse embryonic limb bud and responsive to both IGF-I and -II [23], was investigated. The Western ligand blot analysis of the conditioned medium (CM) from days 1, 3, 5 and 7 of culture revealed the secretion of IGF BP of approx. 35-40, 28-30 and 24-26 kDa. The 35-40 kDa protein which comigrated with the 40 kDa protein in CM of trophoblast cells identified as IGF BP-3. The 28-30 kDa protein was identified as IGF BP-2 by Western immunoblotting with alpha-IGF BP-2 antisera. The 24-26 kDa protein was consistent with the nonglycosylated form of IGF BP-4. Secretion of three IGF BPs were increased with the age of the culture. This suggested that the major IGF BP secreted by differentiating chondrocytes in culture are IGF BP-2, -3 and -4. All three of these IGF BPs were stimulated by both IGF-I and -II. IGF-I was approx. 2-fold more potent than IGF-II. The investigation of the localized production of IGF revealed that chondrocytes, similar to IGF BP, secreted IGF-II in differentiation dependent manner. No IGF-I secretion was identified. Examination of the secretion of solubilized IGF-II receptor by the chondrocytes, in contrast to trophoblasts, failed to reveal the presence of IGF-II receptor in the CM. This suggested that, unlike many other cells, including trophoblasts, chondrocytes do not secrete solubilized IGF-II receptor. In summary, the present results suggested an interactive autocrine/paracrine action of IGF BP and IGF-II in the chondrocytes, while the IGF-I action is predominantly endocrine.

Neurite promoting activity of insulin, insulin-like growth factor I and nerve growth factor on spinal motoneurons is astrocyte dependent.

Mouse motoneurons were isolated from dissociated E15 mouse spinal cord and grown on polyornithine-coated round coverslips in a growth medium (DMEM/F12) supplemented with progesterone, trans-ferrin, selenium, horse serum and muscle extract. Astrocytes from newborn mouse neopallium were grown on rectangular coverslips. The motoneuron neurite growth was determined at day 8 of culture by counting, using the light microscope, the intersections produced by neurites radiating from the perikaryon placed centrally in a graticule eyepiece of concentric circles. The mean intersections for cultures without addition of astrocytes, insulin, insulin-like growth factor I (IGF-I) or nerve growth factor (NGF) was 12.6 +/- 0.8. When astrocytes on a separate coverslip were introduced from day 1, there was a small increase in neurite growth (16.3 +/- 0.9). The neurite growth was further increased significantly with the addition of insulin (27.3 +/- 1.4), IGF-I (31.5 +/- 1.4) or NGF (21.8 +/- 1.1) to cultures with astrocytes. Insulin, IGF-I or NGF in the absence of astrocytes did not greatly increase the neurite growth. We conclude that insulin, IGF-I and NGF promote neurite growth through some interactions with astrocytes.

Effects of astrocytes, insulin and insulin-like growth factor I on the survival of motoneurons in vitro.

We isolated motoneurons from E15 dissociated mouse spinal cord by density centrifugation and planted them onto poly-ornithine-coated coverslips in a growth medium (DMEM/F12) supplemented with progesterone, transferrin, selenium, horse serum and muscle extract. Under these conditions only 28% of the motoneurons survived for 8 days. When living astrocytes on a separate coverslip were introduced into dishes containing motoneurons, there was a two-fold increase in neuronal survival. The addition of insulin and insulin-like growth factor I (IGF-I) to such cultures alone or together, still further increased motoneuron survival, but this did not happen in the absence of astrocytes. We conclude that (a) astrocytes exert a trophic role in the survival of spinal motoneurons, (b) the effect does not require physical contact of the cells, and (c) insulin and IGF-1 have neurotrophic activity for motoneurons, an effect possibly mediated by living astrocytes.

Potentiation of epidermal growth factor-induced differentiation of cultured human placental cells by insulin-like growth factor-I.

Insulin-like growth factor-I (IGF-I) potentiates epidermal growth factor (EGF)-stimulated placental lactogen (hPL) secretion by cultured placental cells. In this study we have examined the effects of EGF and IGF-I, alone or in combination, on the differentiation of placental cells in culture and correlated this differentiation with hPL secretion. Addition of EGF (10 ng/mL) or IGF-I (100 ng/mL) alone in serum-free medium was associated with enlargement of the BhCG-positive (differentiated cytotrophoblast marker) mononucleated trophoblast cells. Concomitant addition of IGF-I and EGF resulted in more marked enlargement of the BhCG-positive cells, aggregation of the enlarged cells, and early syncytiotrophoblast formation. Measurement of hPL in the medium revealed that the stimulatory effect (P less than 0.05) of EGF on hPL secretion by total placental cells was proportional to the stimulatory effect of EGF on cell differentiation, as revealed by the obliteration of its stimulatory effect on hPL by BhCG-positive cells. The augmented stimulatory effect of EGF on hPL secretion by all cells in the presence of IGF-I was decreased (P less than 0.05) when expressed per number of human chorionic gonadotropin (BhCG)-positive cells. The dose-response curves of hPL stimulation by IGF-I in the presence of EGF revealed that the decreased effect of IGF-I on hPL secretion by BhCG-positive-staining cells was due to the difference in magnitude (approximately 1.5 times) of stimulation of BhCG staining of and hPL secretion by the cells. These results extend our previous suggestion that IGF-I in placenta, in addition to its effect on hPL secretion, affects cell differentiation; however, the two effects may not be interdependent.

Differential effects of insulin-like growth factors I and II on growth, differentiation and glucoregulation in differentiating chondrocyte cells in culture.

Insulin-like growth factors I and II have been shown differentially to affect the growth and carbohydrate metabolism of differentiating cartilage developed from mouse embryonic limb buds in organ culture. To gain insight into the relative importance of IGF-I and II actions in different stages of development of cartilage we have established a primary culture of differentiating chondrocytes from mouse embryonic limb buds. Trypsin digested limb bud cells from 9-11 day old mouse embryos differentiated into chondrocytes by 5-7 days in culture. At all stages of differentiation, distinct receptors of IGF-I and II were observed. IGF-I stimulated growth and sulphate incorporation of the non-differentiated and differentiated chondrocytes. IGF-II stimulated growth of the non-differentiated cells and had no effect on growth or sulphate incorporation by the differentiated cells. IGF-II, however, stimulated the glucose uptake by the cells at all stages of differentiation. These data confirm our previous suggestion that IGF-I in cartilage is the regulator of growth and differentiation, while IGF-II may be an important regulator of glucose metabolism in the tissue.

Epidermal growth factor enhancement of insulin-like growth factor-I-induced down-regulation of insulin-like growth factor I receptor in cultured placental trophoblastic cells.

Epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) synergistically stimulate placental lactogen (hPL) secretion by placental cells. To understand the mechanism of actions we have investigated a possible heterologous regulatory effect of EGF and IGF-I on each other's receptors. Pretreatment of the cells with IGF-I had no effect on [125I]-EGF binding or the down-regulation of EGF receptor. Pretreatment of the cells with EGF, concomitantly with IGF-I, had no effect on [125I]-IGF-I binding but it augmented the IGF-I down-regulation of IGF-I receptor. The time required to initiate the IGF-I-induced down-regulation of IGF-I receptor was reduced by 4 h in the presence of EGF. IGF-I-down-regulated decreased (P less than 0.05) receptor numbers were further decreased (p less than 0.05) in the presence of EGF. These results suggested that the synergistic effect of EGF and IGF-I seen in hPL secretion by placental cells is not due to direct heterologous hormone-receptor interactive effects. However, the effects seen may be due to a differentiating effect of EGF sensitizing the cells for responsiveness to IGF-I.

Increased autophosphorylation of insulin-like growth factor-I and insulin receptors in placentas of diabetic women.

Autophosphorylation of insulin and insulin-like growth factor (IGF)-I receptors were measured in lectin purified receptor preparations from placentas of normal and diabetic patients. The basal and insulin or IGF-I stimulated phosphorylation of the approximately 94 kD protein, corresponding to beta-subunit of the insulin and IGF-I receptors, were approximately 2 times greater (p less than 0.05) in placentas from diabetic patients with poor glycemic control (as judged by their serum HbA1c level) compared to the normals. The magnitude of IGF-I or insulin stimulation of the phosphorylation of the 94 kD protein was comparable in placentas from both diabetic and normal patients. Immunoprecipitation and immunodepletion of IGF-I receptor by alpha-IR3, a monoclonal antibody to IGF-I receptor, revealed the increased basal phosphorylation of the approximately 94 kD protein in placentas of diabetic patients to be associated with IGF-I and insulin receptors. The magnitude of IGF-I and insulin stimulated phosphorylation of the immunoprecipitated and immunodepleted IGF-I receptor, respectively, was the same in both normal and diabetic patients. These results suggested that the increased basal phosphorylation of the 94 kD protein in placentas from diabetic patients may be intrinsic to IGF-I and insulin receptor, however, the regulatory mechanisms effecting the increase may not be dependent on IGF-I or insulin.

Parallel effects of insulin-like growth factor-II and insulin on glucose metabolism of developing mouse embryonic limb buds in culture.

The present study was undertaken to evaluate the functional significance of the previously observed increase in the level of IGF-II receptors despite the loss of growth promoting activity of IGF-II in differentiated limb buds in organ culture. In the present study IGF-II and insulin at similar concentration (0.1-1 microgram/ml) stimulated the glucose uptake by the tissue and incorporation into glycogen (approximately 2 and 4 times control) and stimulated the activity of glycogen synthase (approximately 2 times control) of the limb buds irrespective of the differentiation stage of the tissues. IGF-I had little or no effect. None of the hormones (IGF-I, II or insulin) had any effect on the CO2 production by the limb buds. These results suggest a regulatory role of IGF-II, complementary or overlapping with insulin, in glucose metabolism of the developing limb buds. The absence of the effects of both IGF-II and insulin on CO2 production by the tissue, however, indicate that the IGF-II and insulin regulation of glucose metabolism of the limb buds is predominantly on glycogen synthesis.

Altered placental insulin and insulin-like growth factor-I receptors in diabetes.

We have compared the characteristics of IGF-I and insulin receptors in placentas of normals and insulin dependent diabetic patients. Specific binding of both IGF-I and insulin in placental membranes from patients with good glycemic control (as reflected by blood hemoglobin content) was unaltered while that in the placental membranes from the patients with poor glycemic control was increased to approximately 20% of the normals. This observed small but significant (p less than 0.05) increase in binding of IGF-I and insulin to placental membranes from diabetic patients with poor glycemic control was further magnified, approximately twice (p less than 0.001) the normal, when the membrane receptors were purified by lectin chromatography. The kinetic analysis of IGF-I and insulin binding in both membranes and lectin purified receptors revealed that the increased binding of insulin and IGF-I to the placentas from diabetic patients with poor glycemic control was due to an approximately 2 fold increase (p less than 0.001-0.05) in the receptor numbers without any significant changes of the affinities. The molecular characteristics of the receptors in these diabetic patients, as revealed by the cross-linking studies, did not reveal any changes when compared to the normals. The parallel changes of IGF-I and insulin receptors, shown here, are in accordance with the homologous nature of these two receptors. The increased receptor numbers of these two interrelated hormones in placentas of diabetics with poor glycemic control may be relevant to the altered placental functions in diabetic pregnancy.

Mouse placental receptor for basic somatomedin following maternal ethanol administration.

We have previously reported a reduction in the basic somatomedin (B-SM) binding activity of day-15 mouse placental membranes following 3 days of acute maternal ethanol administration. In the present experiments, we have investigated the effects of acute maternal ethanol administration early in gestation on the subsequent development of the placental B-SM receptor, and its relationship to alcohol-related embryofetal growth deficits. Following administration of aqueous ethanol (0.0, 3.6, 5.5 or 7.1 ml/kg) by gavage on days 7, 8 and 9 of gestation, there was no evidence of reproductive impairment in alcohol-treated dams, but there was a significant reduction in day-15 embryonic body weight. Crown-rump length was unaffected. There was no treatment-related difference in the percentage specific binding of [125I]-B-SM by day-15 placental membranes, or in maternal serum B-SM concentrations. These observations suggest that embryofetal growth restriction following maternal ethanol administration is not mediated directly by peripheral unresponsiveness of the B-SM receptor, at least when the exposure occurs early in or prior to placental receptor ontogeny.

Binding and degradation of insulin-like growth factors I and II by rat kidney membrane.

We have investigated the binding and degradation of insulin-like growth factors (IGF)/somatomedin by rat kidney membrane using 125I-labeled IGF-I and IGF-II. The binding of IGF-I and IGF-II were specific to their respective kidney membrane receptors with indicated Mr of 130,000 and 250,000, respectively. The IGF-I and IGF-II degrading activities of the kidney membrane were also found to be specific for the respective hormones. Comparison of the binding and degrading kinetics suggested the two systems to be separate. The characterization of the degrading activities revealed the activities to be neutral sulfhydryl proteases which are different from insulin neutral protease. Identity of these proteases as separate from the insulin protease was revealed from the specificity of the degrading enzymes for IGF and the differential inhibitory effect of N-ethylmaleimide on the enzymes compared to insulin protease. In summary, the IGF binding and degrading activities of kidney membrane are two independent systems with specificity for IGF-I or IGF-II, respectively. Additionally, the characterized IGF-degrading systems revealed the enzymes to be different from the previously described insulin protease.

The effects of insulin-like growth factor-I and insulin on placental lactogen production by human term placental explants.

The effects of insulin-like growth factor (IGF)-I and insulin on placental lactogen production (hPL) by term human placental explants were studied. The hPL content in medium and explant decreased rapidly after first 24 hours of culture. The decrease thereafter was gradual and reached a plateau by day 4 of culture. The decrease of HPL content in placental culture has previously been suggested being due to the depletion of a rapidly secreting preformed pool of hPL. Addition of IGF-I (0.1-10 micrograms/ml) and insulin (1-20 micrograms/ml) stimulated the decreased level of hPL in tissue and medium after 24 hours in culture. IGF-I was 10 times more potent than insulin in stimulating hPL. These findings suggest that IGF-I and insulin effects the production of hPL by placenta. The lower potency of insulin may indicate that the effect of insulin on hPL production is via IGF-I receptor.

Insulin-like growth factors (IGF) in liver disease: differential changes of IGF-I and IGF-II.

IGFs are growth hormone-dependent, serum growth factors which are secreted primarily by liver, although other tissues contribute. We have measured IGF levels in serum of patients with primary biliary cirrhosis (n = 28), primary sclerosing cholangitis (n = 10), and alcohol-induced liver disease (n = 16), and compared them to a group of healthy controls (n = 25). Serum IGF-I as measured by radioimmunoassay was significantly decreased in all patient groups to 30% of control. After acid gel chromatography, IGF-II, measured by radioreceptor assay, was slightly decreased (p less than 0.05) in primary sclerosing cholangitis patients, but not in the other liver disease patients, when compared to the controls. The regression of IGF-II vs IGF-I for primary biliary cirrhosis patients was significant, with r = 0.62, p less than 0.01 (n = 27). The mean ratio of IGF-II/IGF-I was significantly different for histologic stage 2 vs stage 3 vs stage 4 primary biliary cirrhosis patients, but stage 2 was not different from control. We suggest low IGF-I values may reflect compromised hepatocyte function, and secretion of IGF-I and IGF-II may be from different cell populations, or controlled by different mechanisms.

Receptors for insulin-like growth factors I and II in developing embryonic mouse limb bud.

Insulin-like growth factors (IGF) or somatomedins (SM) have been classically defined as promoting the actions of growth hormone in skeletal growth. IGF is divided into two groups, IGF-I and II, and are presumed to act via IGF type I (higher affinity for IGF-I and II and very low affinity for insulin) and II (higher affinity for IGF-II than I and no affinity for insulin) receptors, respectively. Recently, a switchover role of IGF-II to I during fetal to adult growth has been suggested. We have investigated the possible transitional role of IGF-II to I in a developing mouse embryonic limb bud organ culture model. In this in vitro system, limb bud develops from the blastoma stage to a well-differentiated cartilage tissue. Both IGF type I and II receptors were found to be present in limb buds at all stages of differentiation. Type I receptor decreased with differentiation while Type II receptor increased. The effect of IGF-I on [3H]thymidine and [35S]sulfate uptake by the tissue increased with differentiation while the effect of IGF-II on [3H]thymidine uptake of the undifferentiated tissue was abolished with differentiation of the tissue. The increase of the IGF-I response with decreased type I receptor may reflect an altered receptor sensitivity (occupancy) during differentiation. The decrease of the IGF-II response with increased type II receptor with differentiation may on the other hand suggest that IGF-II in differentiated tissue no longer acts as a classical growth factor. These results tend to support the hypothesis of the switchover role of IGF-I and II during fetal and adult growth, however, confirmation of the precise role of IGF-I and II in biological growth may have to wait until further studies clarifying the significance of the increased IGF type II receptor in differentiated tissue are made.

Insulin-like growth factors (IGF) I and II in diabetic pregnancy: suppression of normal pregnancy-induced rise of IGF-I.

The concentrations of somatomedins/insulin-like growth factors were measured by a specific radioimmunoassay for insulin-like growth factor-I and a specific radioreceptor assay for insulin-like growth factor-II in sera of term normal and Type 1 (insulin-dependent) diabetic pregnant women and in various cord sera of their newborn infants. Serum insulin-like growth factor-I levels in normal (non-diabetic) maternal serum were higher than in non-pregnant women (486 +/- 26 versus 215 +/- 26 ng/ml). The normal pregnancy-induced increment of insulin-like growth factor-I was markedly reduced in diabetic pregnancy. It was not different in patients with good or poor glycaemic control, as judged by normal or elevated blood levels of haemoglobin A1c content. Insulin-like growth factor-I levels in cord serum of infants of diabetic women with good glycaemic control (86 +/- 11 ng/ml) and poor glycaemic control (91 +/- 19 ng/ml) were significantly higher (p less than 0.01) than in infants of non-diabetic women (43 +/- 42 ng/ml). The fetal birth weight ratios were not significantly correlated with insulin-like growth factor-I levels in cord serum. Serum insulin-like growth factor-II levels in maternal and cord serum in diabetic and normal pregnancy were not different from each other or from normal non-pregnant women. The increment in insulin-like growth factor-I levels in maternal serum in pregnancy may influence placental structure and function. Lack of this increment in maternal diabetes may have direct implication in placental abnormalities in diabetes and indirect implications on fetal development and metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced binding of basic somatomedin by mouse placental membranes following maternal alcohol administration.

The effects of 3 days of maternal ethanol administration on the placenta and on basic somatomedin (B-SM) were investigated in the mouse. Following administration of aqueous ethanol by gavage on days 13, 14 and 15 of gestation, there was no treatment-related difference in embyonic growth or placental weight as seen on day 15. There was a significant reduction in the specific binding of [125I]B-SM by day 15 placental membranes, but no difference in serum B-SM concentrations or in the frequency or severity of degenerative changes in the placenta. We have shown that changing levels of serum B-SM over the normal course of pregnancy correspond closely to patterns of cellular proliferation and aging in the placenta. It is possible that impairment in the binding activity of B-SM receptors contributes to the premature aging observed in term placentas exposed to alcohol during pregnancy in the rodent.

Ontogeny and characterization of basic somatomedin receptors in rat placenta.

We investigated the binding of [125I]basic somatomedin (B-SM) (insulin-like growth factor-I/SM-C in rat placenta. Low but specific [125I]B-SM binding to placenta was detected in rats from the end of the second week (14 days) of gestation. The binding increased until about 17 days of gestation and then reached a plateau. Binding characteristics did not alter during gestation. In contrast to previous observations [125I]B-SM binding to the tissue was competed more effectively by B-SM than multiplication stimulating activity (a rat counterpart of IGF-II). Insulin competed for the binding at a higher concentration. The Scatchard plot derived from the binding competition data was curvilinear. Autoradiograms of affinity labeled B-SM receptors in placentas at different gestational age subsequent to sodium dodecyl sulfate-gel (7.5%) electrophoresis revealed labeled constituents with approximate mol wt greater than 330 K and 140 K in the presence of reductant and greater than 330 K in the absence of reductant. Detailed analysis of the receptor in term placenta subsequent to 5-13% gradient gel containing sodium dodecyl sulfate revealed two more labeled components (mol wt, 250 K and 36 K) irrespective of the reductant. However, the intensity of the 250 K and 36K was low compared to 140 K and 330 K components. These results suggest that B-SM receptor in rat placenta, similar to human placenta, binds preferentially to type I or 140 K subunit of the 330 K oligomeric SM receptor.