A sensitive enzyme-linked immunosorbent assay (ELISA) for testosterone: use of a novel heterologous hapten conjugated to penicillinase.

A microplate enzyme-linked immunosorbent assay (ELISA) has been developed for the measurement of testosterone in plasma. The assay uses a heterologous system consisting of a novel hapten 4-(17 beta-hydroxy-3-oxoestra-4,9-dien-11 beta-yl)butanoic acid (1) conjugated to penicillinase (beta-lactamase). The key reaction in the synthesis of the hapten was the cuprate-mediated 1,4-conjugate addition on 3,3,17,17-bis-ethylenedioxy-5 alpha,10 alpha-oxido-estr-9(11)-ene by the Grignard reagent derived from trimethyl 4-bromoorthobutyrate; this regiospecifically introduces the 11 beta-butanoate function. The hapten-penicillinase conjugate was used in the assay in conjunction with the immunoglobulin G (IgG) fraction derived from a previously characterized, highly specific, antitestosterone serum raised against a testosterone-19-O-carboxymethyl ether-bovine serum albumin (T-19-O-CME-BSA) conjugate. This unique system represents one incorporating three elements of structural heterology: bridge, site, and ring heterology between the antigen hapten and enzyme-linked hapten. The limit of detection was 10 pg of testosterone with a sensitivity range between 15 and 1,000 pg. A low level of cross-reactivity with 5 alpha-dihydrotestosterone (6.17%) and 11 beta-hydroxytestosterone (1.03%) was noted. No interference was noted with other common androgens, estradiol, or progesterone. The sensitivity and selectivity observed in the assay may be attributable to the selection of penicillinase as the enzyme marker and the elements of conformational heterology between the antigen-linked and enzyme-conjugated steroid haptens.     

Development and validation of competitive ELISA to determine follicular fluid progesterone concentrations

A simple, direct and reliable heterologous ELISA was developed and validated to determine follicular fluid progesterone concentrations in 10- to 20-mm antral follicles in heifers. A competitive ELISA was developed, using a policlonal antisera raised in New Zealand white rabbits and horseradish peroxidase as label. Standard curve covered a range between 0 and 1 ng per well. The intra- and inter-assay coefficients of variation (CV) were 6.54 and 8.27%, respectively (n = 10). The low detection limit was 1 pg per well with a sensitivity of 50% binding 83.17 pg per well. Comparison of ELISA with RIA showed a correlation coefficient of 0.98. A total of 34 follicles obtained from heifers in the follicular phase of the estrous cycle were tested, and the mean progesterone concentration was 86.72 +/- 20.39 ng/ml. These results were similar to those previously reported for the same species, age, follicular size and stage of cycle.     

Ultra sensitive quantitation of endogenous oxytocin in rat and human plasma using a two-dimensional liquid chromatography-tandem mass spectrometry assay

Oxytocin (OT) is a neuropeptide with an extremely low endogenous level (low pg/ml) in human plasma. It is very challenging to develop a highly sensitive assay to measure endogenous OT, including radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA). Electrospray ionization (ESI) liquid chromatography–tandem mass spectrometry (LC–MS/MS) can provide high-throughput and selective methods for quantification of peptides in biological samples. A novel and highly sensitive two-dimensional LC–MS/MS (2D-LC–MS/MS) assay combining solid-phase extraction (SPE) has been developed and validated for the determination of endogenous OT in both human and rat plasma. The lower limit of quantification (LLOQ) was 1.00 pg/ml for human and 50.0 pg/ml for rat. Human plasma diluted with water (1:6, v/v) was successfully optimized as a surrogate matrix for human to prepare standard curves without endogenous interference. The extraction efficiency and absolute recovery were above 65.8% using the HLB SPE procedure, and matrix effects were lower than 12%. The method was validated in the range of 1.00–250 pg/ml for human plasma and 50.0–10,000 pg/ml for rat plasma with precision less than 12.7% and accuracy less than 7%.     

A radioimmunoassay for rat ghrelin: evaluation of method and effects of nonylphenol on ghrelin secretion in force-fed young rats

Antiserum YJC 13-31 against the rat ghrelin conjugated to bovine serum albumin (BSA) was produced in the rabbit and a double antibody radioimmunoassay (RIA) for ghrelin has been developed. Characterization results of this antiserum revealed no cross-reaction with human growth hormone and somatostatin. Weak cross-reactions with insulin (0.1%), rat growth hormone (0.1%) and glucagon (0.3%) were observed, which scarcely interfered the assay system. The sensitivity of this RIA was 5 pg per assay tube. With the rat serum samples, the within-assay precision was 7.1% and the between-assay precision was 12.3%. The RIA was also available to detect the ghrelin in rat tissue extracts with good parallelism to the rat ghrelin standard. In application, the serum ghrelin and corticosterone levels in weaned rats were measured by RIA. Gavage of saline was sufficient to raise serum ghrelin from 2.6 +/- 0.18 to 6.7 +/- 0.7 ng/ml (P < 0.01). Gavage with nonylphenol (NP) suppressed the elevation of serum ghrelin levels in a dose-dependent manner. Besides, gavages of saline elevated the serum levels of corticosterone from 108.8 +/- 13.5 to 188.7 +/- 23.5 ng/ml (P < 0.01) but the elevation effects of corticosterone from gavages were overcome by NP in the low dose of 50 mg/kg. It can be speculated that ingestion of NP is harmful to young animals during growth and environmental adaptation.     

Radioimmunoassay of arginine vasopressin in the plasma and urine.

We introduced the radioimmunoassay (RIA) of arginine vasopressin (AVP) with standard AVP and antiserum to AVP (both Calibiochem). The sensitivity of the system was increased from the declared 4pg to 1 pg per tube by preparing AVP-125I of high specific activity (about 1,500 mCi/mg) and by modifying the reaction conditions. The sensitivity of the method was adequate for measuring AVP in urine and in concentrated plasma extracts, even under physiological conditions. Reliability of the results depended upon maintenance of approximately the same osmolarity in all the RIA samples. The mean plasma AVP level, uncorrected for AVP extraction losses, was 1.52 +/- 0.20 pg/ml for an ad libitum fluid intake; in fluid deprivation it rose in proportion to the osmolarity of the plasma to 5.83 +/- 0.42 pg/ml at 12 hours and to 19.09 +/- 4.51 pg/ml at 36 hours. Extraction recovery of added AVP was about 63%. The urinary AVP concentration varied according to the patients' state of hydratation from undetectable values at UOsm less than 200 mOsm/1 to a mean 16.5 +/- 7.9 pg/ml in the presence of an ad libitum fluid intake and to 29.1 +/- 7.5 pg/ml after 12 hours' and 117.2 +/- 13.7 pg/ml after 36 hours' deprivation of fluids.     

Radioimmunoassay of 7 alpha-methyl-19-nortestosterone and investigation of its pharmacokinetics in animals

A method for the measurement of 7 alpha-methyl-19-nortestosterone (7MENT) in serum/plasma by radioimmunoassay (RIA) is described. The antiserum, raised against 7 alpha-methyl-19-nortestosterone-3-O-oxime-bovine serum albumin, had a low titer (final dilution = 1:4500) and low affinity (Ka = 1.17 x 10(9) l/mol) but showed little or no cross-reactivity with several of the steroids tested. The sensitivity of the RIA was 28.2 pg/ml and the mean recovery of added cold steroid was 86 to 100%. Intra- and inter-assay coefficients of variation ranged from 4.3 to 7.3% and 7.3 to 8.4%, respectively. This RIA was used to follow plasma 7MENT levels after a single i.v. injection of the steroid in rats and rabbits. The metabolic clearance rates (MCR) of 7MENT as determined from the plasma disappearance curve for rats and rabbits were 50 l/day and 336 l/day, respectively. The MCR of 7MENT in rats and rabbits lies in the same range as for testosterone. When compared to other nortestosterone derivatives such as norethisterone, 7MENT is metabolized relatively faster.     

Radioimmunoassay for insulin-like growth factor I (IGF-I) using biosynthetic IGF-I

We produced antiserum to insulin-like growth factor I (IGF-I), and developed a specific and sensitive radioimmunoassay (RIA) for IGF-I using the biosynthetic IGF-I. This antiserum to IGF-I was specific for IGF-I; no cross-reactivities with multiplication stimulating activity, porcine insulin or human growth hormone (hGH) were detected. The sensitivity was 10-25 pg/tube with 50% displacement at 125 pg/tube. The intra- and inter-assay coefficients of variation for IGF-I were 5.4 and 9.7%, respectively. The plasma IGF-I levels as determined by RIA in normal adults (N = 46), patients with active acromegaly (N = 31), and pituitary dwarfs (N = 31) were 21.6 +/- 1.0, 157.3 +/- 17.0, and 2.5 +/- 0.3 ng/ml (Mean +/- SEM), respectively, indicating the levels were GH-dependent. The plasma IGF-I levels were significantly increased from 2.2 +/- 0.2 to 26.5 +/- 3.2 ng/ml after hGH administrations for three consecutive days in five pituitary dwarfs. The IGF-I levels were low in patients with hypothyroidism and liver cirrhosis, but were normal in patients with chronic renal failure. These data confirm previous reports and this radioimmunoassay proves useful in evaluating plasma IGF-I levels.     

二氢玉米素核苷组细胞分裂素的放射免疫测定法

本文报道二氢玉米素核苷（ＤＨＺＲ）组细胞分裂素放射免疫测定法（ＲＩＡ）的研制结果。以（３Ｈ）二氢玉米素作示踪剂,测得免抗ＤＨＺＲ抗血清的效价为１：１３７０（Ｂ％＝３０％）。该抗血清主要与本组细胞分裂素发生交叉反应。回收率为９６．９％,灵敏度为１２ｆｍｏｌ ＤＨＺＲ／管,检测线性范围为０．１￣１００ｐｍｏｌＤＨＺＲ／管。批内误差ＣＶ＝４．３,批间误差ＣＶ＝２．０％。对基于同一免抗血清的ＤＨＺＲ组细胞     

The measurement of neuropeptide Y in discrete hypothalamic and limbic regions of male rhesus macaques with a human NPY-directed antiserum

The distribution of neuropeptide Y (NPY) in microdissected brain regions of male macaques was quantified with a specific radioimmunoassay (RIA). The RIA consisted of a specific antiserum (R31) against human NPY that could detect 7 pg/tube with an IC50 of 125 pg/tube at a final dilution of 1:20,000. Varying amounts of rabbit and monkey mediobasal hypothalami yielded parallel [125I]NPY displacement curves in the assay and similar chromatographic elution profiles with those of synthetic human NPY. The NPY activity in acid extracts of discrete brain regions in castrate and castrated-testosterone-treated rhesus males was highest in mediobasal hypothalamus, followed by more rostral hypothalamic regions and amygdaloid nuclei. Testosterone did not alter NPY levels in any of the brain areas that we examined.     

Determination of 9alpha, 11beta prostaglandin F2 in human urine. combination of solid-phase extraction and radioimmunoassay

This paper describes a new iodine-125 radioimmunoassay of 9alpha ,11beta-PGF2, and its use for the determination of urinary 9alpha,11beta-prostaglandin F2 after a selective one-step solid-phase extraction. The newly reported immunoassay is based on the use of 125I-tyrosyl methyl ester derivative of 9alpha,11beta-PGF2 and specific polyclonal antibody raised in rabbits.The assay detected as lowas 0.85 pg/tube 9alpha,11beta-PGF2, and the antibodyshowed lessthan 0.01 cross-reaction with PGF-ring metabolites (e.g., 8-iso-PGF2alpha, PGF2alpha 2,3-dinor-6-keto-PGF1alpha, and 5 more PGF-ring compounds). Both the intra-assay, and inter-assay CVs were lessthan 20% for internal controls containing low, medium and high concentrations of 9alpha,11beta-PGF2. Immuno-HPLC analysis showed a very low ratio of specific immunoreactivity in both non-extracted urine (6.5%), and in urine extracted on C18-silicacartridge (14.8%). By contrast, approximately 80% specific immunoreactivity could be achieved by using C2-silicaas the sorbent, acetonitrile: water (15:85, v/v) as wash solvent, and ethyl acetate as eluent of 9alpha,11beta-PGF2.This extraction procedure enabled a reasonably high extraction efficiency of 80.4 +/- 0.855 (mean +/- SEM, n=82), as determined by 3H-9alpha,11beta-PGF2. The new SPE/RIA method was applied for the determination of urinary 9alpha,11beta-PGF2 values in 50 healthy human volunteers. For the concentration and for the excretion rate 37.52 +/- 4.61 pg/ml (mean +/- SEM), and 3.50 + 0.35 ng/mmol creatinine (mean +/- SEM), respectively, was measured.The specificity of the SPE/RIA method was supported by the observed 69% decrease in 9alpha, 11beta-PGF2 excretion rate after acetylsalicylic acid treatment. The effect of nicotinic acid, a PGD2-stimulatory agent, was monitored by the urinary excretion of 9alpha ,11beta-PGF2 in 6 patients, by using the new SPE/RIA method. In patients responding with flushing symptoms nicotinic acid induced an increase of the urinary excretion of 9alpha,11beta-PGF2 in the range between 11% and 187%. In summary, the combination of the newly developed specific [125I] radioimmunoassay with solid-phase extraction on C2-silica cartridges enables the specific, sensitive, and reliable determination of 9alpha,11beta-PGF2 in human urine without the need for further laborious chromatographic purification before radioimmunoassay.     

Radioimmunoassay of nafarelin ([ 6-(3-(2-naphthyl)-D-alanine)]-luteinizing hormone-releasing hormone) in plasma or serum

A procedure which is suitable for the radioimmunoassay (RIA) of nafarelin [( 6-(3-(2-naphthyl)-D-alanine)]-luteinizing hormone-releasing hormone) in plasma or serum at concentrations as low as 50 pg/ml is described. Antiserum was prepared by replacing the pyroglutamyl portion of nafarelin with glutaric acid, coupling the product to keyhole limpet hemocyanin, and immunizing rabbits with the resulting conjugate. At a dilution of 1:30,000 the binding was approximately 50%. The antibodies did not cross react with luteinizing hormone-releasing hormone. For RIA, 125I-labeled analyte was used as the tracer and charcoal was used to separate the free and the bound fractions. No purification of samples was required prior to RIA. Accuracy of the method was assessed by adding known quantities of nafarelin to nafarelin-free plasma and determining the ratio of measured to added analyte. Linear regression analysis for the concentration range 0.050-5.00 ng/ml yielded a regression equation of y = 1.01x - 0.066 and a correlation coefficient of 0.997. At 0.050 ng/ml the CV was 11.3% (interassay). Additional validation was obtained from an in vivo study in which [3H]nafarelin was administered to monkeys and plasma profiles were determined by RIA, by high-performance liquid chromatography (HPLC), and by an HPLC-radiochemical method. The results obtained by RIA agreed well with those obtained by the HPLC methods.     

Effects of phytoestrogen-coumestrol on lipid and carbohydrate metabolism in young ovariectomized rats may be independent of its estrogenicity

Two groups of young ovariectomized female rats received one of two treatments. The first group was fed coumestrol in lab chow (200 microg of coumestrol per day) for 14 days; the second group received coumestrol (40 mg/L) via perfusion medium. There was a significant increase (78% compared with the control group) in the uterine weight after coumestrol treatment, which supports the estrogen-like activity of coumestrol. Phytoestrogen diminished the liver and skeletal muscle glycogen contents by 18% and 29%, respectively, and increased the blood glucose level by 24%. Glycogenolytic activity of coumestrol was observed when it acted directly on the liver areas. Although phytoestrogen did not influence insulin and glucagon blood level, liver and to some degree muscle susceptibility to insulin (measured as hormone binding by insulin receptors) was decreased. Coumestrol increased the content of triglycerides in muscle by 113% and enhanced the liver lipid synthesis from glucose by 179%. Liver cholesterol concentration was increased both after coumestrol feeding (by 12%) and when it acted directly on the liver (by 16%). These observations suggest that coumestrol is in general anabolic with regard to lipid and catabolic within-carbohydrate metabolism of young ovariectomized female rats. Based on the results of this study, it is concluded that influence of coumestrol on lipid and carbohydrate metabolism of ovariectomized rats is in part not related to its estrogenic action.     

Radioimmunoassay for insulin-like growth factor II (IGF-II)

Insulin-like growth factor II (IGF-II) levels in human plasma were measured in physiological and pathological conditions by radioimmunoassay (RIA) with biosynthetic IGF-II. This RIA was specific for IGF-II and cross-reactivity with IGF-I was 1%. The sensitivity was 15 pg/tube with 50% displacement at 50 pg/tube. The intra- and inter-assay coefficients of variation for IGF-II were 6.3 and 9.3%, respectively. The plasma IGF-II levels in normal adults, patients with hypopituitarism and patients with active acromegaly were 589.6 +/- 15.8, 800.9 +/- 45.6 and 330.3 +/- 24.3 ng/ml, respectively. After human growth hormone (hGH) treatment in hypopituitarism, IGF-II slightly increased, but not significantly. After adenomectomy in patients with acromegaly, IGF-II significantly decreased. These data indicate that IGF-II concentrations in plasma were partially GH dependent. This GH dependency was less than that of IGF-I. IGF-II was low in patients with anorexia nervosa and with liver cirrhosis and high in patients with renal failure. In two cases with extrapancreatic tumor-associated hypoglycemia, plasma IGF-II was increased to 1123.8 and 843.5 ng/ml, and returned to normal after tumor resection. These data showed that IGF-II was partly dependent on GH and nutritional conditions and that IGF-II was the most likely cause of some cases of hypoglycemia with extrapancreatic tumor. This specific and sensitive RIA of IGF-II would be useful in evaluating its physiological and pathological role in plasma and tissue.     

A non-chromatographic radioimmunoassay of prugesterone in serum

Convenient methodology based on separation of progesterone from alcoholic neutral steroids by means of a sulfation-procedure has been developed for the radioimmunoassay (RIA) of progesterone in male and female serum. When coordinated with our previously published nonchromatographic procedure for the RIA of estrone and estradiol in serum, all 3 seteroids can be determined in the same specimen. Validation of the procedure was based on: 1. Agreement between results obtained using TLC and sultation to fractionate progesterone (r=0.98; b=0.86), 2. accurate recovery of different quantities of progesterone added to serum, 3. independence of the concentration of progesterone and volume of serum used for assay, 4. low procedural blanks (3.6 ± 1.3 pg), 5. low intraassay (9.7 – 10.3%) and interassay (11.0 – 11.6%) variability and 6. correspondence of observed values for progesterone in male serum (108 ± 20 pg/ml) and in female serum (follicular, 285 ± 149 pg/ml; luteal, 3.46±1.45 ng/ml) with those reported previously by others.     

Fluorescence and chemiluminescence enzyme immunoassays of 17 alpha-hydroxyprogesterone in dried blood spotted on filter paper

Enzyme immunoassays for 17 alpha-hydroxyprogesterone (17-OHP) were developed. Horseradish peroxidase (HRP), glucose oxidase (GOD), invertase (INV) and glucose-6-phosphate dehydrogenase (G6PDH) were used as label enzymes. Double antibody coated beads or tubes were used for separating the bound and free fractions. Antisera used were prepared by using 4-carboxyethylthio-17-OHP and 3-carboxymethyl oxime-17-OHP-bovine serum albumin as immunogens. The bridge heterologous system was more sensitive than other site heterologous and homologous systems. The minimum amounts of 17-OHP detected were 0.25 and 1.0 pg/tube for fluorescence EIAs using HRP and GOD, and 0.1, 10 and 0.1 pg/tube for chemiluminescence EIAs using GOD, INV and G6PDH, respectively. The reproducibility and correlation with RIA were also studied. The present study demonstrates the feasibility of a neonatal screening for congenital adrenal hyperplasia.     

Effect of forage on the content of phyto-oestrogens in bovine milk

Phyto-oestrogens are believed to have a range of beneficial effects on predominant Western diseases. A few studies on phyto-oestrogens in milk exist and show that the composition can be affected by feeding. Therefore, the aim was to study how feeding of lucerne and grass/clover silages (GCSs) affects the concentration of phyto-oestrogens in bovine milk. Sixteen Danish Holstein cows were assigned to a 4 × 4 latin square design with four cows per treatment per period of 3 weeks. The four treatment diets were lucerne silage (LS), 2/3 lucerne silage and 1/3 maize silage (2/3LS), 1/3 lucerne silage and 2/3 maize silage (1/3LS) and GCS. Milk was collected at the end of each period and feed samples on day 6, 13 and 20 in each experimental period. Milk and pooled feed samples were analysed for the concentration of isoflavones, coumestans and lignans. The content of isoflavones was higher and the content of coumestrol lower in the GCS diet than in LS, 2/3LS and 1/3LS diets. For the LS, 2/3LS and 1/3LS diets, the concentration of coumestrol and secoisolariciresinol increased with the proportion of lucerne while the concentration of isoflavones was similar across the diets. The concentrations of the formononetin, daidzein and equol in the milk were significantly higher for the GCS diet than for the LS, 2/3LS and 1/3LS diets. In particular, the concentration of equol was 62-291 times higher for GCS. The concentration of coumestrol was significantly lower for the GCS diet compared to the LS, 2/3LS and 1/3LS diets. No pattern for the concentration of lignans was observed. In conclusion, a high concentration of isoflavones, particularly equol, and a low concentration of coumestrol were measured in the milk from the GCS diet. In contrast, a low concentration of isoflavones and a high concentration of coumestrol were measured in the milk from the LS, 2/3LS and 1/3LS diets. However, the concentration of phyto-oestrogens in bovine milk is low compared to food sources rich in phyto-oestrogens but the high concentration of equol could possibly be of therapeutic importance.     

Elisa for salivary and plasma estriol in pregnancy

A competitive, sensitive, and rapid enzyme-linked immunoadsorbent assay (ELISA) was developed for the determination of estriol in saliva and in plasma. Horseradish peroxidase (HRP) was used as the label enzyme; separation between free and bound steroid was carried out by insolubilized antibody prepared by adsorbing purified IgG of rabbit anti-6-oxoestriol-6-(0-carboxymethyl)oxime-BSA on polystyrene balls. The enzyme activity was measured by a colorimetric reaction using o-phenylenediamine dihydrochloride and hydrogen peroxide as substrate. The sensitivity of the assay was 12 pg/tube.In order to compare ELISA to RIA estriol estimations in different biological fluids, we selected six women during normal pregnancy, from the 30th to the 40th week of gestation. Salivary estriol was assayed by direct and extraction methods, while the corresponding plasma samples of the same subjects were analyzed only for unconjugated estriol by an extraction method.A good agreement was found between the results obtained by RIA and ELISA: r=0.897, p <0.001 between direct RIA and direct ELISA in saliva; r=0.909, p < 0.001 between extraction RIA and direct ELISA in saliva; and r=0.916, p < 0.001 between extraction RIA and extraction ELISA in plasma. A good correlation (r=0.793, p<0.001) was present between plasma samples by RIA and saliva samples by ELISA (direct method).These results indicate that: 1. ELISA is a reliable method for the determination of estriol in plasma and saliva. 2. Saliva samples can be used for the assay of estriol and therefore for the assessment of fetal conditions during pregnancy.     

Radioimmunoassay for a new phenothiazine derivative and its application.

Fluphenazine-4-chlorophenoxy-isobutyrate ester, a new phenothiazine derivative was synthesized in the Institute for Drug Research Budapest. Radioimmunoassay was developed for the therapeutic monitoring of the drug level after intramuscular depot injection. The fluphenazine hapten was coupled to BSA by mixed-anhydride method. Antisera were produced to this conjugation in New-Zealand white rabbits and were tested for the antibody-titer. The specificity was tested by the cross-reaction with phenothiazine-analogues and other psychotropics. Strong cross-reaction was found with compounds possessing piperazine in side chain (trifluoperazine, perphenazine), but other psychotropic drugs did not react. Tritium-labelled trifluoperazine (spec. activity: 3.5 TBq/mmol) was used as a tracer in the radioimmunoassay. The detection limit was 75 pg with a CV of < 5% in 50 microliters plasma sample (equivalent to 1.5 ng/ml concentration) and a standard curve in the 3 ng/ml-50 ng/ml GYKI-22441 concentration range showed a CV of < 10%. Preliminary pharmacokinetic study was performed in Beagle dogs after intramuscular depot injection with GYKI-22441 in sesame oil in a dose of 0.1 mg/kg. The GYKI-22441 concentration of the plasma samples were measured by the RIA method during a 28-day interval after the treatment and was evaluated by the MultiCalc Immunoassay Data Management program (Pharmacia).     

A novel radioimmunoassay of 7-oxo-DHEA and its physiological levels

A novel radioimmunoassay (RIA) of unconjugated 7-oxo-dehydroepiandrosterone (7-oxo-DHEA) in human serum was developed for the first time. This steroid is an intermediate in the biosynthesis of immunomodulatory 7-hydroxylated DHEA metabolites, and has been shown to possess thermogenic properties. The method employs polyclonal rabbit antiserum to (19E)-3beta-hydroxy-7,17,19-trione-19-O-(carboxymethyloxime):BSA conjugate and a homologous radioiodinated derivative with tyrosine methyl ester. The cross reactivity of the antiserum with structurally closest 7-hydroxyepimers of DHEA was lower than 1.7%, with DHEA 0.4%, with all other related steroid less than 0.4%. The method includes ether extraction of serum (0.5 ml), followed by RIA. Its detection limit was 0.06 pmol (18 pg)/tube, the average intra- and inter-assay coefficients of variation were 4.1% and 8.3%, respectively. Mean recovery of serum spiked with 7-oxo-DHEA varied between 78.8% and 112%. Its levels in three serum pools were compared with a low-resolution gas chromatography-mass spectrometry method with satisfactory results. The method has been used for determination of 7-oxo-DHEA in serum samples of 215 subjects (91 males and 124 females) without overt endocrine disorders, aged 5-71 years. The over-all mean+/-S.D. was 0.280+/-0.227, the median 0.239 nmol/l. No significant sex differences were recorded. The only group which differed significantly from all other ones were males below 10 years, significantly lower values than in other age groups were found also in the first two age groups of females.     

Development of a sensitive enzymeimmunoassay (EIA) for FSH determination in bovine plasma.

A highly sensitive enzymeimmunoassay (EIA) procedure for FSH determination in bovine plasma on microtiterplates using the biotin-streptavidin amplification system and the second antibody coating was developed. Biotin was coupled to FSH and used to bridge between streptavidin-peroxidase and the immobilized antiserum in the competitive assay. The EIA was carried out directly in 50 microl of bovine plasma and compared with an established radioimmunoassay (RIA) employing 100 microl plasma. Same FSH standards and FSH specific antiserum were used in both procedures. FSH standards prepared in hormone free plasma were used. The sensitivity of the EIA procedure was 6.25 pg/well FSH which corresponded to 125 pg/ml plasma; the 50% relative binding sensitivity was seen at 200 pg/well. In comparison to RIA, the EIA was at least four times more sensitive besides requiring 6 times less FSH specific antiserum. Plasma volumes for the EIA ranging from 12.5 to 50 microl did not influence the shape of the standard curve even though a slight drop in the OD450 was seen with higher plasma volumes. When both EIA and RIA methods were used to measure FSH in cows, the levels were detectable only by the EIA procedure. The assay detects high and low plasma FSH levels within the physiological variation as well as changes in plasma FSH after stimulation with a GnRH analog. In conclusion, in addition to being non-radioactive and low cost in nature, the method offers several advantages over the conventional FSH RIA procedure; these are (a) higher sensitivity, (b) less labour and time saving, (c) more economical use of precious FSH antiserum and (d) long shelf-life of the biotinyl-FSH label (in contrast to the short half life of iodinated FSH in RIA).