Immunoassays are widely used for measuring gonadotropins, including luteinizing hormone (LH), as these are both specific and sensitive. Because LH is microheterogeneous it has been claimed that the specificity of monoclonal antibodies used in two-site immunoassays can limit their clinical utility. Furthermore, we reported earlier a common genetic variant form of LH due to amino acid alterations in the LHbeta gene that is poorly or not recognized by antibodies directed against epitopes present in the intact molecule. We here report the result of an LH epitope mapping using 30 different monoclonal antibodies. The antigenic area affected by the amino acid alterations is fairly large, as antibodies to the two intact domains are able to sandwich each other. Combinations of alpha-beta or beta-beta antibodies generally provide alternatives for unbiased detection of circulating LH and some have reasonably good discrimination of human chorionic gonadotropin. The beta-beta combinations exhibit a peculiarity in urine determinations as they detect the urinary beta-core fragment. Our aims were to study the altered immunoreactivity caused by the amino acid changes and to design two-site LH assays fully capable of recognizing the biologically active LH variant. We also conclude that the variability in recognizing the universally occurring LH variant is the most important factor contributing to the widely documented LH immunoassay discrepancies.
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C Nilsson, M Seppala, and K Pettersson
D Swolin-Eide, A Nilsson, and C Ohlsson
It is well known that high levels of glucocorticoids cause osteoporosis and that physiologic levels of growth hormone (GH) are required for normal bone remodeling. It has been suggested that glucocorticoids regulate GH-responses via the regulation of GH-receptor expression. The aim of the present study was to investigate whether cortisol plays a role in the regulation of GH-receptor expression in cultured human osteoblasts. The effect of serum starvation and cortisol on GH-receptor expression was tested in human osteoblast (hOB)-like cells. Serum starvation for 24 h resulted in an increase in GH-receptor mRNA levels (90 +/- 1% over control culture). Cortisol increased GH-receptor mRNA levels in a dose-dependent manner with a maximal effect at 10(-6)M. The stimulating effect of cortisol on GH-receptor mRNA levels was time-dependent, reaching a peak 12 h after the addition of cortisol (126 +/- 29% over control culture) and remaining up to 12 h later. The increase in GH-receptor mRNA levels was accompanied by an increase in 125I-GH binding which reached a maximum at 24 h (196 +/- 87% over control culture). In conclusion, glucocorticoids increase GH-receptor expression in hOB-like cells. Further studies are needed to clarify whether glucocorticoid-induced regulation of the GH-receptor is important in human bone physiology.
J. Bentham, C. Ohlsson, A. Lindahl, O. Isaksson, and A. Nilsson
In the present study a double-staining technique was developed to investigate simultaneous GH and insulin-like growth factor-I (IGF-I) binding to chondrocytes in a monolayer cell culture.
Rat tibial epiphyseal chondrocytes were isolated by enzymatic digestion and cultured in monolayer. GH and IGF-I were labelled with biotin. The affinity of the biotin-labelled ligands was compared with unlabelled ligands in a radioreceptor assay.
To study the distribution of GH and IGF-I binding in the monolayer, chondrocytes were incubated with biotinylated ligands with or without an excess of unlabelled ligands, followed by incubation with Vectastain ABC complex, which was then reacted with diaminobenzidine (DAB). Double staining was accomplished by carrying out the first reaction with DAB in the presence of nickel ammonium sulphate to give a black precipitate, followed by incubation with the second ligand, then ABC complex and finally DAB in the absence of nickel ammonium sulphate to give a brown stain. The presence of type-II collagen was demonstrated by immunohistochemistry and used as a marker for differentiated chondrocytes.
Biotin-labelled GH and biotin-labelled IGF-I exhibited dose-dependent displacements of 125I-labelled GH and 125I-labelled IGF-I respectively from the chondrocytes in a radioreceptor assay. The displacement curves were identical to those of unlabelled ligands indicating that the affinity was unaltered. Binding of biotinylated GH to cells was seen throughout the culture in regions where there was little or no type-II collagen staining. IGF-I binding was predominantly localized to cells at high density; areas which also showed a high degree of staining for type-II collagen.
The different locations of binding suggest that epiphyseal chondrocytes in monolayer culture comprise a heterogeneous cell population and that IGF-I and GH have different target cells.
Journal of Endocrinology (1993) 137, 361–367
C. Ohlsson, A. Nilsson, O. G. P. Isaksson, and A. Lindahl
The influence of various culture conditions was studied on the effect of GH and insulin-like growth factor-I (IGF-I) on DNA and matrix synthesis in epiphyseal rat chondrocytes in monolayer culture.
Chondrocytes from enzymatically digested rat tibia epiphyseal growth plates were seeded in 48-well culture plates and precultured for 10 days in Ham's F-12 medium supplemented with 1% (v/v) newborn calf serum and 1% (v/v) of a serum substitute. After preculture, the medium was changed to Ham's F-12 medium supplemented with 1% serum from hypophysectomized rats, and the effect of GH and IGF-I on DNA synthesis ([3H]thymidine incorporation) and matrix production ([35S]sulphate uptake) was studied during an additional 96-h culture period. Isotopes were present during the last 24 h of culture.
Both hGH and IGF-I stimulated DNA synthesis in a dose-dependent manner. A maximal effect of GH was seen at a concentration of 25 μg/l (60 ± 11% stimulation over control) and for IGF-I at 10 μg/l (162 ± 12%). The stimulatory effects of the same concentrations of human GH (hGH) and IGF-I on [35S]sulphate uptake were 135 ± 25 and 320 ± 42% respectively. In-vitro pulse labelling revealed that GH did not produce a response during the first 3 days of culture (after addition of GH) but was effective during days 4 and 5 of culture. In contrast, IGF-I was effective throughout the culture period. Pretreatment of cells with GH or IGF-I for 2·5 days showed that GH but not IGF-I produced a sustained effect on [3H]thymidine uptake.
In order to study the influence of cell density on the effect of GH and IGF-I on DNA synthesis, the effect of added peptides was evaluated after different preculture periods (5–15 days). A maximal stimulatory effect of hGH was seen at a cell density of 150 000–300 000 cells/cm2. GH had no significant effect at a low (< 100 000 cells/cm2) or a high (>400 000 cells/cm2) cell density. The magnitude of the stimulatory effect of IGF-I was the same at densities between 10 000 and 250 000 cells/cm2, but was reduced at higher cell densities (over 250 000 cells/cm2).
Chondrogenic properties of cells that had been cultured for 15 days were verified in vitro by positive alcian blue staining and identification of type II collagen, and in vivo by development of cartilage nodules in nude mice.
The results from the present study clearly show that GH and IGF-I both stimulate DNA synthesis and matrix production in epiphyseal chondrocytes in monolayer culture. The results also demonstrate that expression of the effect of GH is highly dependent upon the culture conditions.
Journal of Endocrinology (1992) 133, 291–300
C. Ohlsson, A. Nilsson, O. Isaksson, J. Bentham, and A. Lindahl
The effects of tri-iodothyronine (T3) and insulin-like growth factor-I (IGF-I) on [3H]thymidine incorporation, alkaline phosphatase (ALP) activity and IGF-I receptor mRNA levels were studied in rat epiphyseal chondrocytes cultured in monolayer.
Chondrocytes from enzymatically digested rat tibia epiphyseal growth plates were seeded in monolayer culture and precultured for 7–14 days in Ham's F-12 medium supplemented with 10% (v/v) newborn calf serum and 1% (v/v) of a serum substitute. After preculture the medium was changed to Ham's F-12 medium containing 1% (v/v) serum from hypophysectomized rats, and the effects of T3 and/or IGF-I on DNA synthesis ([3H]thymidine incorporation), ALP activity (a late marker of differentiated epiphyseal chondrocytes) and IGF-I receptor mRNA levels were studied.
ALP activity was increased by T3 in a dose-dependent manner with a maximal response at 10 μg T3/1 (678 ±86% compared with control culture). The increase in ALP activity was accompanied by a concomitant decrease in [3H]thymidine incorporation (52 ±14% compared with control culture). Human GH (hGH; 50 μg/l) and IGF-I (25 μg/l) had no stimulatory effect on ALP activity. However IGF-I (10 μg/l) exerted an inhibition on the T3 (10 μg/l)-induced increase in ALP activity (64 ± 9% compared with T3-treated culture). T3 (3 μg/l) inhibited the increase in [3H]thymidine incorporation caused by 25 μg IGF-I/l(51 ± 13% compared with IGF-I-treated culture). Furthermore, IGF-I receptor mRNA levels were increased by 10 μg T3/l (137 ±4·2% compared with control culture) while no effect of hGH (50 μg/l) or IGF-I (25 μg/l) was demonstrated.
Both T3 and IGF-I were shown to interact with epiphyseal chondrocytes and both substances seemed to affect cell proliferation and maturation and therefore longitudinal bone growth. Furthermore, the results indicated that IGF-I is important for proliferation of the cells while T3 initiates the terminal differentiation of epiphyseal chondrocytes.
Journal of Endocrinology (1992) 135, 115–123
JM Kindblom, O Nilsson, T Hurme, C Ohlsson, and L Savendahl
Indian Hedgehog (Ihh) has been reported to control the rate of cartilage differentiation during skeletal morphogenesis in rodents through a negative feedback loop involving parathyroid hormone related protein (PTHrP). The role of Ihh and PTHrP in the regulation of human epiphyseal chondrocytes is unknown. The aim of the current study was to examine the expression and localization of Ihh and PTHrP in the human growth plate at various pubertal stages. Growth plate biopsies were obtained from patients subjected to epiphyseal surgery and the expression of Ihh and PTHrP was detected by immunohistochemistry. We show that Ihh and PTHrP are expressed mainly in early hypertrophic chondrocytes in the human growth plate. The levels of expression of Ihh and PTHrP are higher in early stages of puberty than later. Our results suggest that Ihh and PTHrP are present in the human growth plate and that Ihh and PTHrP may be involved in the regulation of pubertal growth in humans.
D Swolin-Eide, J Dahlgren, C Nilsson, K Albertsson Wikland, A Holmang, and C Ohlsson
Events occurring early in life or prenatally are able to play important roles in the pathogenesis of diseases in adult life. Different sorts of stress or hormonal influences, during particular periods of pregnancy, may result in persisting or transient changes in physiology. Glucocorticoids are used for the treatment of a variety of diseases, to promote organ maturation and to prevent preterm delivery. Glucocorticoids are also known to affect skeletal growth and adult bone metabolism. The aim of the present study was to investigate whether exposure to dexamethasone (Dex) during fetal life has any effect on skeletal growth and/or bone mineral density in adult rat offspring. Pregnant rats were given injections of either Dex (100 micro g/kg) or vehicle on days 9, 11 and 13 of gestation. Dex-exposed male but not female rat offspring showed transient increases in crown-rump length and tibia and femur lengths at 3-6 weeks of age. In contrast, the cortical bone dimensions were altered in 12-week-old female but not male Dex-exposed offspring. The areal bone mineral densities of the long bones and the spine, as determined by dual X-ray absorptiometry, and trabecular as well as cortical volumetric bone mineral density, as measured using peripheral quantitative computerized tomography, were unchanged in both male and female Dex-exposed offspring. In conclusion, prenatal Dex exposure affects skeletal growth in a gender-specific manner, while the mineralization of bones is unaffected in both male and female offspring.
C Nilsson, D Swolin-Eide, C Ohlsson, E Eriksson, HP Ho, P Bjorntorp, and A Holmang
Leptin is involved in regulating food intake, energy balance and bone formation. Increasing evidence suggests that leptin is also involved in fetal growth and development. The aim of this study was to determine if increased maternal leptin is followed by changes in body composition, skeletal growth or hormonal regulation in the adult rat offspring. Pregnant rats were given injections of either human recombinant leptin (3.5 mg/kg, i.p.) or vehicle on days 8, 10 and 12 of gestation. Both genders of leptin-exposed offspring showed significantly reduced adipose tIssue weight at adult age. Skeletal growth and cortical bone dimensions were significantly reduced. Circulating testosterone levels were significantly increased in female leptin-exposed offspring, and male leptin-exposed offspring had significant testicular enlargement. No significant effects were seen on circulating leptin levels or hypothalamic protein levels of the leptin receptor. The results demonstrate that maternally administered leptin is involved in fetal growth and development, leading to lean offspring with reduced skeletal growth.
Patricia Forcinito, Anenisia C Andrade, Gabriela P Finkielstain, Jeffrey Baron, Ola Nilsson, and Julian C Lui
The mammalian growth plate undergoes programed senescence during juvenile life, causing skeletal growth to slow with age. We previously found that hypothyroidism in rats slowed both growth plate chondrocyte proliferation and growth plate senescence, suggesting that senescence is not dependent on age per se but rather on chondrocyte proliferation. However, one alternative explanation is that the observed slowing of growth plate senescence is a specific consequence of hypothyroidism. We reasoned that, if delayed senescence is a general consequence of growth inhibition, rather than a specific result of hypothyroidism, then senescence would also be slowed by other growth-inhibiting conditions. In this study, we therefore used tryptophan deficiency to temporarily inhibit growth in newborn rats for 4 weeks. We then allowed the animals to recover and studied the effects on growth plate senescence. We found that structural, functional, and molecular markers of growth plate senescence were delayed by prior tryptophan deficiency, indicating that the developmental program of senescence had occurred more slowly during the period of growth inhibition. Taken together with previous studies in hypothyroid rats, our findings support the hypothesis that delayed senescence is a general consequence of growth inhibition and hence that growth plate senescence is not simply a function of time per se but rather depends on growth.
C Andersson, ML Lydrup, M Ferno, I Idvall, J Gustafsson, and BO Nilsson
The role of oestrogen receptor (ER) beta in vascular function remains unclear. With the use of a specific ERbeta antibody we have now, using immunocytochemistry, visualized ERbeta in different parts of the vascular tree. In about 70% of medial smooth muscle cells of female rat aorta, tail artery and uterine artery, nuclear immunoreactivity to ERbeta was observed. In these vessels endothelial cells also expressed ERbeta. Vascular expression of the ERalpha subtype was lower than that of ERbeta. In aorta and tail artery, no immunoreactivity towards ERalpha was observed, while in uterine vessels occasional medial smooth muscle and endothelial cells expressed this ER subtype. ERbeta and alpha expression in uterine vessels was independent of the stage of the oestrous cycle, suggesting that variations in uterine blood flow occurring during the cycle are independent of ER density. The regional distribution of ERalpha, as determined by immunocytochemistry, was supported by measurements of ERalpha levels by enzyme immunoassay. In the uterine artery, the level of ERalpha was several times higher (P<0.001) than that of aorta and tail artery (10.1+/-1.7 fmol/mg protein in the uterine artery vs 3.3+/-1.0 and 0.5+/-0.5 fmol/mg protein in aorta and tail artery respectively). Thus, a prominent nuclear expression of ERbeta was observed in the vascular wall of several parts of the vascular tree, while ERalpha predominantly was expressed in uterine vessels, suggesting that ERbeta and alpha may have different roles in vascular function.