Somatomedin-C, physical fitness, and bone density

Somatomedin-C (Sm-C) or insulin-like growth factor-I, GH and physical fitness decline with age. Physical fitness and muscle strength are important determinants of bone density, and the age-related decline in bone density may be related in part to a decline in fitness and muscle strength. Also, Sm-C has been shown to stimulate osteoblasts in vitro and may effect skeletal muscle mass. We postulated that the age-related decline in GH and Sm-C levels may be related to an age-related decline in physical fitness and/or muscle strength, and the effect of physical fitness and muscle strength on bone may be mediated by Sm-C. We, therefore, examined the relationship between circulating GH and Sm-C levels and physical fitness, as determined by predicted maximal oxygen uptake (VO2max) in 134 normal women, 34 of whom were postmenopausal. In a subgroup of 62 women overall muscle strength was estimated as the sum of the Z-sores for biceps, quadriceps, and grip strength. Overall muscle strength correlated with GH levels (r = 0.28; P less than 0.02), but not with Sm-C levels. There was a significant positive relationship between plasma Sm-C levels and VO2max in all women (r = 0.47; P less than 0.001) and in the postmenopausal group alone (r = 0.05; P less than 0.01). Although there was a significant negative relationship between Sm-C and age (r = -0.36; P = 0.001), VO2max was a better independent predictor than age (r = 0.47; P = 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of biosynthetic human growth hormone on insulin action in individual tissues of the rat in vivo

Excessive endogenous production or exogenous administration of human growth hormone (hGH) causes insulin resistance at both the hepatic and extrahepatic levels. However, which extrahepatic tissues are involved have not been defined. We have examined the diabetogenic action of authentic biosynthetic hGH on whole body glucose disposal, hepatic glucose output, and glucose metabolism in individual peripheral tissues. The use of a highly purified preparation of the hormone allowed us to examine the isolated effects of 22K hGH. The euglycemic hyperinsulinemic (approximately 100 mU/L) clamp plus 3H-2-deoxyglucose technique was used to quantitate the effects of hGH on insulin action in vivo. Administration of biosynthetic hGH at a dose of 10 IU/kg/24 h for 48 hours in male Wistar rats (approximately 340 g) produced a highly significant decrease in the steady state clamp glucose infusion rate (GIR) when compared with controls (8.1 +/- 0.6 v 18.7 +/- 0.7 mg/kg/min, P less than .001), reduced insulin-mediated suppression of hepatic glucose output (Ra) (3.9 +/- 0.6 v 0.7 +/- 0.3 mg/kg/min, P less than .05) and a decreased clamp glucose disposal rate (Rd) (12.0 +/- 0.4 v 18.10 +/- 1.1 mg/kg/min, P less than .001). There was a significant decrease in insulin-mediated glucose uptake as indicated by tissue accumulation of [3H]-2-deoxyglucose phosphorylation in diaphragm and hindlimb muscles. Insulin action was more substantially reduced in muscles (approximately 50%) than in adipose tissues (approximately 20%). These studies confirm that the diabetogenic action of hGH in the rat is due to a combination of inhibition of insulin suppression of hepatic glucose output and inhibition of the uptake and subsequent utilization of glucose in skeletal muscles.

Formation of multilamellar vesicles by addition of tannic acid to phosphatidylcholine-containing small unilamellar vesicles

Tannic acid induces aggregation and formation of multilamellar vesicles when added to preparations of small unilamellar vesicles, specifically those containing phosphatidylcholine. Aggregation and clustering of vesicles was demonstrated by cryo-electron microscopy of thin films and by freeze-fracture technique. Turbidity measurements revealed an approximately one-to-one molar ratio between tannic acid and phosphatidylcholine necessary for a fast and massive aggregation of the small unilamellar vesicles. When tannic acid-induced aggregates were dehydrated and embedded for conventional thin-section electron microscopy, multilamellar vesicles were retrieved in thin sections. It is concluded from morphological studies, as well as previous tracer studies, that tannic acid, at least to a great extent, prevents the extraction of phosphatidylcholine. Multilamellar vesicles were also observed in tannic acid-treated vesicles prepared from total lipid extracts from either rabbit or rat hearts. Substantially more multilamellar vesicles were retrieved in the rabbit vesicle preparation. This difference can probably be explained by the difference in the proportion of the plasmalogen phosphatidylcholine, and possibly the content of sphingomyelin, in lipid extracts of rabbit and rat hearts. It is concluded that the dual effect (reduced extraction and aggregation) of tannic acid on phosphatidylcholines should be taken into consideration when tannic acid is used in tissue preparation.

Dual effect of tannic acid on the preservation and ultrastructure of phosphatidyl choline vesicles

The use of tannic acid has been proposed to improve the preservation of phospholipids in tissues. We investigated the effects of tannic acid on the preservation of small unilamellar vesicles, prepared from sonicated aqueous suspensions of phospholipids. With cryo-electron microscopy it is demonstrated that small unilamellar vesicles are formed after sonication of the phospholipid suspensions. Fixation of vesicles without tannic acid results in extraction of the phospholipids during dehydration and embedding. Fixation of vesicles containing phosphatidyl choline with tannic acid, with or without glutaraldehyde, results in a fast (within a second) aggregation of the vesicles and the resulting sediment can be dehydrated and embedded when a postfixation in osmium tetroxide is carried out. Small unilamellar vesicles fixed in this way are retrieved in thin sections as multilamellar vesicles with a periodicity of about 5 nm for dimyristoylphosphatidyl choline and about 6 nm for dioleoylphosphatidyl choline. By using 14C-phosphatidyl choline it was also demonstrated that tannic acid prevents to a large extent the extraction of phosphatidyl choline during fixation, dehydration and embedding. This dual effect of tannic acid on phosphatidyl choline, aggregation and fixation, should be considered when using tannic acid in tissue preparation.

Quantification of urinary growth hormone (GH) excretion by centrifugal ultrafiltration and radioimmunoassay: appraisal of the relationship between 24 h urinary GH and mean 24 h serum GH levels in normal and abnormal states of GH secretion

We have applied a simple method for the quantification of 24 h urinary GH excretion (24 h UGH), combining centrifugal ultrafiltration and radio-immunoassay (RIA), to an appraisal of the relationship between 24 h UGH and mean 24 h serum GH levels in normal and abnormal states of GH secretion. Forty-four subjects, comprising 13 normal adults, 12 short-statured subjects and 19 subjects with active acromegaly, underwent blood sampling at 20-min intervals and concurrent urine collection for 24 h. Mean 24 h serum GH and 24 h UGH were also determined in four post-menopausal women before and during cyclical oestrogen replacement therapy, and 24 h UGH was measured in six normal men prior to and following the subcutaneous administration of biosynthetic GH (0.2 IU/kg). Each subject's mean 24 h serum GH level was determined by assaying a 'pooled' sample, derived from equal aliquots of the 73 serum samples obtained during the 24 h study. The method for quantification of 24 h UGH employs centrifugal microconcentrators, and involves a 50-fold concentration of urine, followed by dialysis and RIA. Surface adsorptive hormone loss during sample collection and ultrafiltration is minimized by the prior addition of bovine serum albumin to the urine collection container. Immunoreactive GH in ultrafiltered urine dilutes in parallel with the RIA standard curve. GH is stable in urine stored at - 20 degrees C for at least 12 months. There was a highly significant correlation between 24 h UGH and mean 24 h serum GH values obtained from the combined population of normal adults (including the post-menopausal women during oestrogen therapy) and short-statured subjects (r = 0.69, P less than 0.0001). A significant correlation was also found in short-statured subjects alone (r = 0.63, P less than 0.05). In contrast, there was no significant correlation between 24 h UGH and mean 24 h serum GH in subjects with active acromegaly, and their 24 h UGH values were not distinguishable from those of the 'non-acromegalic' subjects. A significant increase in 24 h UGH occurred in the post-menopausal women given cyclical oestrogen replacement therapy (9.7 +/- 2.6 (mean +/- SE) to 24.6 +/- 1.0 muIU/mmol creatinine, P less than 0.02), reflecting the increase in their mean 24 h serum GH levels (0.8 +/- 0.3 to 5.3 +/- 0.7 mIU/l, P less than 0.01). Twenty-four hour UGH increased from 4.6 +/- 0.6 to 17.1 +/- 2.1 muIU/mmol creatinine (P less than 0.002) in the men given biosynthetic GH. Twenty-four hour UGH measurements reflect mean 24 h serum GH levels in normal adults and short-statured subjects. While the measurement of 24 h UGH shows promise as an investigative tool, our results cast doubt on its use in the diagnosis of acromegaly.

The pharmacokinetics, safety and endocrine effects of authentic biosynthetic human growth hormone in normal subjects

The pharmacokinetics, safety and endocrine effects of an authentic human growth hormone (bio-hGH), produced by the expression of genomic hGH in a mammalian cell line, were studied in six healthy young men who were administered 0.2 U/kg/day subcutaneously for five consecutive days. Changes in sodium balance and in thyroid function were studied during the week of bio-hGH administration and safety parameters were monitored over a 3-week period. Growth hormone levels reached a mean (+/- SD) peak of 106 +/- 10 mIU/l at 3.3 +/- 0.5 h following the first dose and resulted in a significant rise of somatomedin C. free fatty acids, fasting blood glucose and insulin concentrations. Bio-hGH administration resulted in a significant increase in body weight (80.0 +/- 4.5 to 81.1 +/- 4.3 kg; P less than 0.01) which was associated with a marked reduction in urinary sodium excretion (196 +/- 38 to 45 +/- 20 mmol/day; P less than 0.025). Serum T3 increased during bio-hGH administration and was associated with reciprocal changes in free thyroxine and TSH concentrations. Cardiac, hepatic, renal, biochemical, haematological, endocrinological and immunological functions remained normal throughout the study. No antibodies to hGH or to host cell protein developed during the study. The results show that bio-hGH is safe in the short term, well tolerated, possesses pharmacokinetic and biological properties similar to pituitary hGH, and has distinct effects on sodium balance and on thyroid function. This study stresses the need to monitor patients for effects on sodium retention, carbohydrate metabolism and thyroid function when using hGH doses of 1.0 U/kg/week (40 U/m2/week) or more in patients with GH responsive short stature.

Intermediary structures during membrane fusion as observed by cryo-electron microscopy

Lipidic phases, containing 'lipidic particles' (dioleoylphosphatidylethanolamine/cholesterol/dioleoylphosphatidylcho lin e and cardiolipin/dimyristoylphosphatidylcholine in the presence of Ca2+) have been investigated by preparing thin films from a suspension of sonicated vesicles. These thin films were vitrified and observed 'directly' by cryo-electron microscopy in their hydrated form. The thin films show various fusion products and fusion intermediates such as lipidic particles.

Specificity of two-site immunoassays

When cross-reaction in two-site immunoassays was investigated both theoretically and experimentally it was found that such systems do not always result in enhanced specificity. Computer simulation studies indicated that substances which display negligible cross-reaction in a radioimmunoassay could produce an assay response identical to that of the analyte in a two-site immunoassay using excess antibody. Cross-reactivity in two differing two-site immunoassays was compared to that obtained in radioimmunoassays using the same monoclonal antibodies for human chorionic gonadotrophin. In addition to the effects of excess antibody, cross-reactivity was observed in one of the two-site immunoassays which could not have been predicted from the specificity of the antibodies or cross-reactivity in the radioimmunoassays. The unexpected cross-reaction of the beta subunit of human chorionic gonadotrophin in the assay resulted from an apparent alteration in the specificity of one of the antibodies following binding of the beta subunit to the second antibody. These studies emphasise the complexity of binding reactions in two-site immunoassays.

Phospholipid, nature's own slide and cover slip for cryo-electron microscopy

Thin films of surface-active compounds, with or without particulate material, can be obtained by immersing and withdrawing a bare specimen grid from a solution/suspension of the compound. Immediately after withdrawing the grid, thinning of the film starts. Thinning is initially powered by gravity and capillary forces and will proceed in thin films (less than 100 nm) driven by intermolecular forces until the London-van der Waals attractive forces come to an equilibrium with electrostatic repulsion of similarly charged surfaces of the film. With small unilamellar vesicles prepared from the phospholipid dimyristoyl phosphatidyl choline (DMPC) the draining behaviour of these films was studied by cryo-electron microscopy. Small unilamellar vesicles were observed within the film as well as the coalescence of these vesicles into sheets ('leaky' membrane fusion). Sheets dominate the images when films are allowed to drain for longer periods (greater than 3 min). Thin films were formed on grids from catalase crystals suspended in a DMPC suspension and vitrified by cooling. High-resolution information was obtained by electron diffraction at low temperature and under low-dose conditions from catalase crystals surrounded by small vesicles as well as from catalase crystals surrounded by sheets of DMPC. In the latter case the water content drops from 99% (DMPC in small vesicles) to less than 30% (DMPC in sheets) during draining. Ferritin was added to a DMPC suspension and thin films were prepared and vitrified. After prolonged draining ferritin molecules were deposited in layers with a stepwise increase in thickness. Draining of thin films has thus a dehydrating effect as well as a sorting and ordering effect. These effects must be considered when using surface-active compounds at air-water interfaces as a slide and cover slip for electron microscopy.

Heterophilic antibodies: a problem for all immunoassays

We verified that antibody-binding substances in serum that interfere in two-site immunoassays involving murine antibodies are heterophilic antibodies. Incubation of serum containing heterophilic antibodies and a murine monoclonal antibody to human choriogonadotropin (hCG) leads to formation of a series of soluble immune complexes. We investigated the recognition of hCG by reagent antibody in the presence of heterophilic antibodies and found this recognition to be diminished. Consequently, about 30% of serum samples containing heterophilic antibodies falsely appear to contain increased concentrations of hCG. The effect on analyte recognition probably results from steric inhibition of hCG binding to complexed antibody. Heterophilic antibodies detected with a murine antibody also bound immunoglobulin from several other species but did not bind all of those tested.

Heterophilic antibodies: a problem for all immunoassays

We verified that antibody-binding substances in serum that interfere in two-site immunoassays involving murine antibodies are heterophilic antibodies. Incubation of serum containing heterophilic antibodies and a murine monoclonal antibody to human choriogonadotropin (hCG) leads to formation of a series of soluble immune complexes. We investigated the recognition of hCG by reagent antibody in the presence of heterophilic antibodies and found this recognition to be diminished. Consequently, about 30% of serum samples containing heterophilic antibodies falsely appear to contain increased concentrations of hCG. The effect on analyte recognition probably results from steric inhibition of hCG binding to complexed antibody. Heterophilic antibodies detected with a murine antibody also bound immunoglobulin from several other species but did not bind all of those tested.

Incidence and specificity of interference in two-site immunoassays

Using a modified "two-site" immunoradiometric assay, termed an "interference assay," we have demonstrated the occurrence of non-analyte antibody-binding substances in approximately 40% of serum samples. These substances multivalently bind antibodies from any of several species at a site other than the antigen-binding site. Using a two-site immunoradiometric assay for human choriogonadotropin, we have investigated their effect on analyte quantification. In this system these antibody-binding substances mimic the presence of analyte; when analyte is actually present, they can also cause over- or underestimates. Addition of excess nonspecific immunoglobulin from an appropriate species eliminates this interference. However, the amount of nonspecific immunoglobulin added to an assay system may not always be enough to block interference in all samples.

Incidence and specificity of interference in two-site immunoassays

Using a modified "two-site" immunoradiometric assay, termed an "interference assay," we have demonstrated the occurrence of non-analyte antibody-binding substances in approximately 40% of serum samples. These substances multivalently bind antibodies from any of several species at a site other than the antigen-binding site. Using a two-site immunoradiometric assay for human choriogonadotropin, we have investigated their effect on analyte quantification. In this system these antibody-binding substances mimic the presence of analyte; when analyte is actually present, they can also cause over- or underestimates. Addition of excess nonspecific immunoglobulin from an appropriate species eliminates this interference. However, the amount of nonspecific immunoglobulin added to an assay system may not always be enough to block interference in all samples.

Error in laboratory reference limits as shown in a collaborative quality-assurance program

Laboratories participate in collaborative quality-assurance programs to maintain and improve the quality of their diagnostic assays, but little attention has been paid to diagnostic quality in these programs. We used a national quality-assurance program to assess the quality of laboratory reference intervals as exemplified by triiodothyronine, thyroxin, and thyrotropin immunoassays. The limits of the reference intervals used by laboratories bear virtually no relationship to laboratory bias, i.e., whether assays read "high" or "low." Further, correcting assay results from different laboratories for the reference limits used increases rather than decreases interlaboratory scatter. We conclude that the analytical quality of immunoassays now exceeds the quality of the reference limits supplied to clinicians to assist diagnosis, and that nationally or internationally defined reference limits would therefore provide more information at less cost than do individual laboratory reference limits.

Error in laboratory reference limits as shown in a collaborative quality-assurance program

Laboratories participate in collaborative quality-assurance programs to maintain and improve the quality of their diagnostic assays, but little attention has been paid to diagnostic quality in these programs. We used a national quality-assurance program to assess the quality of laboratory reference intervals as exemplified by triiodothyronine, thyroxin, and thyrotropin immunoassays. The limits of the reference intervals used by laboratories bear virtually no relationship to laboratory bias, i.e., whether assays read "high" or "low." Further, correcting assay results from different laboratories for the reference limits used increases rather than decreases interlaboratory scatter. We conclude that the analytical quality of immunoassays now exceeds the quality of the reference limits supplied to clinicians to assist diagnosis, and that nationally or internationally defined reference limits would therefore provide more information at less cost than do individual laboratory reference limits.

Localization of human pituitary hormones by multiple immunoenzyme staining procedures using monoclonal and polyclonal antibodies

Mouse monoclonal and rabbit polyclonal antibodies to human pituitary hormones were applied together to sections of normal and neoplastic human pituitary tissue. Binding sites were revealed with species-specific immune reagents combined with various enzymes (peroxidase, alkaline phosphatase, and beta-D-galactosidase). The enzymes were developed separately to give differently colored end-products. Where two hormones were present in the same cell, a mixed color was produced. Up to four hormones could be immunostained in a single section. Multiple immunoenzymatic staining has great potential for the analysis of plural antigen production by single cells and relationships between cells producing different antigens.

Circulating insulin-like growth factor I levels in newborn premature and full-term infants followed longitudinally

Longitudinal circulating levels of insulin-like growth factor I (IGF-I) were measured by radioimmunoassay after acid/ethanol extraction of serum or plasma in 44 appropriate-for-gestational age (AGA) premature infants, 7 small-for-gestational age (SGA) premature infants and 9 AGA full-term infants. The subjects were divided into cohorts with gestational age at birth 26-29 weeks, 30-33 weeks, 34-37 weeks and 38-42 weeks (full-term). The premature infants in this study exhibited diminished growth as compared with normal intrauterine growth. In all but the earliest premature infant cohort there was an immediate fall from the mean fetal IGF-I level, as reflected by the cord value, to a basal postnatal circulating level of IGF-I. The basal level of circulating IGF-I in premature infants was related only to gestational age. It increased slowly from 25 weeks gestation until four weeks after full-term equivalent and was independent of time of birth. Full-term infants were distinguished from early premature infants by the occurrence of a prominent postnatal surge in circulating IGF-I levels that was characterised by a significant (P less than 0.02) increase between day 1 and days 10-15. The SGA and AGA infants in the 34-37 week cohort showed similar profiles of circulating IGF-I with no significant difference in cord values between the two groups.

Covert cross reactants in a two-site immunoassay studied with monoclonal antibodies

A one-step two-site immunoradiometric assay for the measurement of free beta subunit of human chorionic gonadotrophin (beta-hCG) was developed using monoclonal antibodies. The immobilized antibody was specific for free beta subunit and the radiolabeled antibody recognized both intact human chorionic gonadotrophin (hCG) and free beta subunit. Although the level of hCG "cross-reaction" was low when studied using conventional techniques, the apparent beta-hCG content of samples was found to be inversely proportional to the hCG level. From both experimental evidence and computer simulation studies this was found to be due to the binding of hCG to the limited amount of 125I-labeled antibody present. The term covert cross reactants has been introduced to describe substances which bind to only one of the antibodies in a two-site immunoassay. When establishing such an assay the effect of covert cross reactants on the response of an analyte should be investigated.

The production of monoclonal antibodies to human chorionic gonadotrophin and its subunits

The difficulties encountered in producing highly specific antisera to human chorionic gonadotrophin (hCG) were overcome by the use of hybridoma technology. A panel of monoclonal antibodies directed toward hCG and its subunits was produced. Of the four antibodies which were fully characterized, one recognized the intact hCG molecule only, a second recognized only the free beta-subunit, a third recognized only the free alpha-subunit and the fourth bound to the beta-subunit of hCG both when it was in the free form and when it was associated with the alpha-subunit forming the intact hCG molecule. There was no significant cross-reaction of any of these antibodies with the pituitary glycoprotein hormones. The four antibodies had high binding affinities which should permit their use in immunoassays for measurement of circulating levels of hCG and its subunits.

The production of high affinity monoclonal antibodies to human growth hormone

The primary aim of this work was to produce specific monoclonal antibodies to human growth hormone (hGH) for use in a diagnostic RIA of hGH levels in serum. Three different schedules were used for immunization of BALB/c mice and the splenocytes from each mouse were fused with myeloma cells Sp 2/0 Ag 14. Each fusion resulted in the production of hundreds of hybridomas secreting hGH-directed antibodies. Six antibodies have been fully characterized and have been grouped into pairs which recognize 3 different epitopes on the hGH molecule. One pair exhibits no cross reaction with the structurally related placental hormone, human placental lactogen (hPL), a second pair has low cross reaction with hPL (1.6-3%) and a third pair reacts equally well with hGH and hPL indicating binding to a common epitope in the 2 molecules. The highest affinity antibody, 74/6, which has an affinity constant of 4.4 X 10(10) l/mol and 3% cross-reactivity with hPL, has been used to establish a RIA for serum hGH measurements. Evidence is provided that hGH levels measured in this assay correlate well with those obtained in a conventional rabbit antiserum assay.

Use of immunoaffinity chromatography for purification of 125I-labeled human prolactin

We assessed a simple method for purifying 125I-labeled human prolactin, taking advantage of the abundant supplies of monoclonal antibodies available. 125I-Labeled human prolactin purified by immunoaffinity chromatography is compared with that purified by gel filtration on Sephadex G-100. We used monoclonal antibodies to prolactin to prepare the affinity chromatography columns. Prolactin was radiolabeled by the Chloramine T method, purified by each of the above procedures, and the binding and displacement characteristics were studied in radioimmunoassays in which either monoclonal antibodies or a rabbit anti-prolactin serum was the first antibody. A nonimmune fraction of 125I-labeled prolactin that co-eluted with the immunoreactive hormone from Sephadex G-100 was removed by affinity chromatography, which increased the antibody binding of 125I-labeled prolactin in the radioimmunoassay in the absence of unlabeled antigen (B/T0, in percent) twofold or more, increased the assay sensitivity, and increased the slope of antigen displacement measured by the 50% intercept. Several advantages make this the purification method of choice.

Use of immunoaffinity chromatography for purification of 125I-labeled human prolactin

We assessed a simple method for purifying 125I-labeled human prolactin, taking advantage of the abundant supplies of monoclonal antibodies available. 125I-Labeled human prolactin purified by immunoaffinity chromatography is compared with that purified by gel filtration on Sephadex G-100. We used monoclonal antibodies to prolactin to prepare the affinity chromatography columns. Prolactin was radiolabeled by the Chloramine T method, purified by each of the above procedures, and the binding and displacement characteristics were studied in radioimmunoassays in which either monoclonal antibodies or a rabbit anti-prolactin serum was the first antibody. A nonimmune fraction of 125I-labeled prolactin that co-eluted with the immunoreactive hormone from Sephadex G-100 was removed by affinity chromatography, which increased the antibody binding of 125I-labeled prolactin in the radioimmunoassay in the absence of unlabeled antigen (B/T0, in percent) twofold or more, increased the assay sensitivity, and increased the slope of antigen displacement measured by the 50% intercept. Several advantages make this the purification method of choice.

A monoclonal antibody suitable for the radioimmunoassay of prolactin in human serum

Monoclonal antibodies directed toward human PRL (hPRL) have been produced by fusion of mouse myeloma cells (Sp2/0-Ag 14) with spleen cells from mice immunized with hPRL. Total immunizing doses of 20 microgram and 64 microgram hPRL resulted in the production of three highly specific hPRL antibodies. The high affinity antibody, with a Ka value of 0.23 X 10(10) M-1, was used to establish a RIA highly suitable for the measurement of hPRL levels in human serum. The correlation of serum hPRL levels measured using the antibody and those in a conventional rabbit anti-hPRL assay was 0.99 (y = 1.16 - 7.2). These results demonstrate that using the mouse hybridoma technique, it is possible to produce high affinity monospecific monoclonal antibody suitable for the measurement of hPRL in human serum.

Lectins used to prepare serum free of glycoprotein hormones for use as a matrix in radioimmunoassay

Hormone-free serum is required for use as a matrix for standards in the radioimmunoassay of hormones. The glycoprotein hormones are difficult to remove from serum by conventional techniques. We exploited the specific binding of carbohydrates by lectins to extract glycoprotein hormones from human serum. Passing serum over Concanavalin A Sepharose efficiently removed lutropin and the beta subunit of choriogonadotropin. Wheat-Germ Lectin Sepharose completely removed these, and also follitropin and thyrotropin. The latter treatment is shown to provide a suitable matrix for standards in radioimmunoassays of the four hormones.