A sensitive and specific enzymeimmunoassay for serum testosterone.

A very sensitive enzymeimmunoassay for testosterone was developed using testosterone-penicillinase conjugate and an antibody to testosterone-3-(O-carboxymethyl)oxime-bovine serum albumin. The specificity of the assay was demonstrated by the fact that estradiol-17 beta, estrone, estriol, progesterone, 17 alpha-hydroxy-progesterone, dehydroepiandrosterone, androstenedione, cortisol and cortisone were ineffective in crossreacting with testosterone while dihydrotestosterone was 8 times less crossreactive as compared to testosterone. The minimum detectable amount of testosterone was 10-15 pg per assay tube. Intra-assay and inter-assay coefficients of variation for samples containing 0.3-6ng/ml of testosterone were 6-8% and 8-10%, respectively. A high degree of correlation (r = 0.97) was observed between serum testosterone values obtained by enzymeimmunoassay and radioimmunoassay. The levels of testosterone in the sera of normal men and women and those in hypogonadal males following stimulation with human chorionic gonadotropin determined by this enzymeimmunoassay appear similar to those reported by other investigators.     

Radioimmunoassay and enzymeimmunoassay of plasma progesterone as monitors of progesterone sponge treatment in ewes

The daily plasma progesterone (P) concentrations achieved during insertion of P (750 mg) sponges into two groups of ewes were examined. Group I received prostaglandin (PG) treatment, which was required to suppress the P production (to levels of < 0.3 ng hormone/ml plasma) from the corpora lutea (CL) of a previous superovulation treatment, following which these Group I ewes and the anestrous Group II ewes were sponge treated. Radioimmunoassay (RIA) and enzymeimmunoassay (EIA) were used to measure the P levels in both groups. Progesterone (750 mg) sponges with and without citric acid impregnation were inserted into all the ewes for 12 days (d). Citric acid lowered the P levels reaching the plasma from the sponges, but it did not mask the characteristic profile (during the treatments) determined by the states of the ewes (single PG and double PG injected, Group I or in the anestrous Group II). The plasma P levels in Group I and II ewes rose to at least 7.0 ng/ml at intervals during treatment. The duration and magnitude of the P concentrations in the plasma were higher in the single PG compared with the double PG ewes during sponge insertion in Group I. The anestrous Group II ewes showed two major peaks (Day 1, P<0.01 and Days 11 to 12, P<0.05) during sponge treatment. A P level > 2.0 ng/ml was maintained over the entire treatment in the single PG and in the anestrous hormone-treated ewes, and was of shorter duration (7 d) in the double PG-treated animals. These endogenous patterns in P profiles of the ewes indicate that the hormone level during sponge insertion varies in magnitude and duration, parameters determined by the physiological/endocrinological state of the ewes at the start of the treatment. The EIA correlated significantly (P<0.001) with the RIA for the measurement of P concentration, when analyzed daily on an individual animal basis.     

A sensitive solid phase enzymeimmunoassay for testosterone in plasma and saliva.

A sensitive, solid phase enzymeimmunoassay suitable for determining testosterone concentrations in samll aliquots of plasma (20 microliter) and saliva (200 microliter) has been developed. A solid phase antiserum raised against a testosterone-11 alpha-hemisuccinate/bovine serum albumin conjugate was prepared by coupling to cyanogen bromide activated cellulose. The "enzyme label" was a covalently linked testosterone/horseradish peroxidase conjugate. The assay had a lower limit of sensitivity of 4pg/assay tube and satisfied accepted criteria of specificity and precision. Testosterone concentrations determined by enzyme-immunoassay were in excellent agreement not only with a gas liquid chromatography/mass spectrometry procedure (r=0.96, n=12) but also with the radioimmunoassay in routine use (r=0.95, n=12). The EIA can therefore replace RIA in both the small clinical laboratory and high throughput service centres for determining plasma and salivary testosterone concentrations. In normal males salivary testosterone concentrations reflected circulating steroid levels and indicated the possibility of assaying saliva rather than plasma in clinical studies.     

A simple enzymeimmunoassay of milk progesterone for monitoring fertility in dairy buffaloes

A simple, sensitive, direct (without extraction) enzymeimmunoassay (EIA) was usec to determine progesterone levels in whole milk samples of 400 Nili-Ravi dairy buffaloes. The mean progesterone values 22 d after A.I. were significantly higher in pregnant (16.6 +/- 9.2 ng/ml) than nonpregnant (below 5 ng/ml) animals. The mean progesterone values were below 0.34 +/- 0.12 (the detection limit) both at estrus and in cases of clinically diagnosed inactive ovaries, 3.18 +/- 1.9 at proestrus, 2.25 +/- 1.2 postestrus and 13.22 +/- 6.74 at Day 10 of the estrous cycle. Twenty buffaloes confirmed pregnant for 2 to 3 mo, had a mean value of 20.3 +/- 4.5 ng/ml. The EIA test is very reliable in the selection of nonpregnant buffaloes (100 %) and the confirmation of inactive ovaries and of estrus. Differential diagnosis of inactive or active ovaries can be made by analyzing two milk samples at a 7-d interval.     

Direct enzymeimmunoassay of progesterone in bovine milk

A sensitive enzymeimmunoassay has been developed for measuring progesterone in unextracted bovine milk. An N-hydroxysuccinimide ester of 11 alpha -hydroxyprogesterone 11-hemisuccinate has been synthesised and used to form conjugates with beta-galactosidase in buffer at pH 7.0. The degree of incorporation of progesterone into the enzyme was demonstrated using (14C)-labelled steroid and by radioimmunoassay binding inhibition. Standard curves of comparable range and sensitivity to radioimmunoassay were obtained in the presence of whole milk taken from a cow at oestrus. These advances have allowed the development of a simple micro-titre plate enzymeimmunoassay of progesterone in whole milk and will be of particular value in determination of pregnancy, prediction of the day of oestrus and diagnosis of reproductive disorders.     

A specific, non-chromatographic radioimmunoassay for human plasma cortisol.

A radioimmunoassay technique has been developed for the measurement of cortisol in a single methylene chloride extract of human plasma without chromatography. The antiserum, obtained by immunizing rabbits with cortisol-3-carboxymethyl-oxime conjugated to bovine serum albumin, had a high affinity (KA = 1.8 X 10(9) 1/mole) and capacity (2.3 X 10(-6) moles/L undiluted serum) for cortisol. The minimum detectable amount determined at the lower 95% confidence limit of the buffer control tubes was 8.3 +/- 4.7 pg/tube and a log dose - logit response standard curve was linear between 20 pg and 20 ng/tube. The antiserum was highly specific for cortisol with only corticosterone, cortisone, 11-deoxycortisol and 21-deoxycortisol showing significant cross-reaction (12.4, 6.6, 3.8 and 3.7%, respectively). The cross-reaction for the other tested naturally occurring and synthetic steroids did not exceed 1%. Regression analysis of cortisol concentration estimates obtained on 20 samples before and after Sephadex LH-20 column chromatography gave a coefficient of correlation (r) of 0.995 and a regression coefficient (b) of 1.04. Recovery of cortisol added to plasma samples was quantitative. The intra-assay error was 8.5% and the inter-assay error averaged 5.7%. The method is simple requiring a single solvent extraction of plasma, therefore permitting large numbers of samples to be handled efficiently by a single technician.     

Oestrus control and early pregnancy diagnosis in the swamp buffalo: comparison of enzymeimmunoassay and radioummunoassay for plasma progesterone

A preliminary study has been undertaken, in order to investigate the suitability of a progesterone assay in blood plasma for oestrus control and pregnancy diagnosis in the swamp buffalo (Bubalus bubalis ). Progesterone was determined both by radioimmunoassay (RIA) and by enzymeimmunoassay (EIA). Values obtained by EIA were considerably lower than values obtained by RIA. This may be partly due to the fact that only RIA values were corrected for procedural losses. Blood samples were taken on day 1 (= day of insemination) and on days 24, 27 and 30 after insemination (p.i.). Additional samples from pregnant animals were taken around day 170 p.i.. Normal progesterone values during oestrus were lower than 0.5 ng/ml, and generally the same low values were found in case of non-pregnancy at days 24, 27 and 30 p.i.. Pregnant animals showed in all cases progesterone concentrations higher than 0.5 ng/ml at days 24, 27 and 30, as well as around day 170 p.i.. These preliminary results indicate that the analysis of progesterone in plasma may be suitable for fertility control in the swamp buffalo. Furthermore we suggest that a modified EIA method can be used as a simple and rapid oestrus detection test under field conditions.     

A quantitative solid-phase enzymeimmunoassay for 13,14-dihydro-15-keto- prostaglandin F2 alpha in plasma.

Enzymeimmunoassays (EIA) can be viable alternatives to radioimmunoassays (RIA). Indeed, from an environmental perspective, EIA are preferable to RIA. Therefore, the purpose of this project was to develop a quantitative EIA for 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) in bovine plasma. Acetylcholine esterase bound covalently to PGFM, rabbit anti-PGFM, mouse monoclonal anti-rabbit IgG, and PGFM were the principle reagents used for the EIA. Validation experiments indicated that: 1) PGFM standard curves, with doses ranging from 391 to 200,000 fg per microtiter well, were linear; 2) assay sensitivity averaged 391 fg per well; 3) for satisfactory results, PGFM had to be extracted from plasma; 4) content of PGFM in ethyl ether extracts of aliquots from serial dilutions of whole plasma with unknown amounts of PGFM and charcoal-stripped plasma supplemented with known amounts of PGFM did not deviate from parallelism with PGFM standard curves in buffer; 5) correlation between EIA and RIA measurements of PGFM in the same plasma samples was .95; 6) the regression of EIA data on RIA data was linear (Y = .93 x + 83.9; r2 = .91); 7) intra- and interassay coefficients of variation were 3.3 and 10.6%, respectively. The EIA developed in this project is a valid and reliable method for quantitating PGFM in extracts of bovine plasma.     

Development of a sensitive enzymeimmunoassay (EIA) for progesterone determination in unextracted bovine plasma using the second antibody technique

A simple direct enzymeimmunoassay (EIA) on microtiter plates for plasma progesterone using the second antibody coating technique and horseradish peroxidase (HRP) as the enzyme label (EIA-HRP) is described and compared with an identical EIA procedure which employed alkaline phosphatase (AP) as the enzyme label (EIA-AP). The assays used antiserum raised against progesterone-7-carboxyethlthioether-BSA in rabbits. Both systems were further compared with the conventional direct progesterone radioimmunoassay (RIA) in regular use. The enzymes HRP and AP were coupled to progesterone-6 beta-hydroxy-hemisuccinate by a mixed anhydride method. While the precision of EIA-HRP was comparable to RIA, the sensitivity in terms of the lowest detection limit obtained in EIA-HRP was about 10 times better than that seen in RIA. Progesterone estimates from plasma samples in EIA-HRP showed good correlation (r = 0.94) with the RIA values and the levels measured in the two systems were identical. Progesterone estimates from plasma samples in EIA-AP were at least three times higher than those obtained by either EIA-HRP or RIA. Thus, only the EIA-HRP but not the EIA-AP was suitable for the reliable direct measurement of progesterone in plasma.     

A sensitive solid phase enzymeimmunoassay for norethisterone (norethindrone) in saliva and plasma

A sensitive, solid phase enzymeimmunoassay suitable for determining norethisterone in small aliquots of plasma (10 μl) and saliva (100 μ1) has been developed. A solid phase antiserum raised against a norethisterone-llα-hemi-succinyl/bovine serum albumin conjugate was prepared by coupling to cyanogen bromide activated cellulose. A norethisterone/horseradish peroxidase conjugate was used as enzyme label, o?-phenylenediamine/hydrogen peroxide being the substrate for colour development. The assay had a lower limit of sensitivity of 3 pg/assay tube and satisfied accepted validation criteria. Norethisterone concentrations determined by enzymeimmunoassay and by a well established radioimmunoassay were in excellent agreement in both plasma (r = 0.993, n = 20) and saliva (r = 0.989, n = 15). Plasma and salivary norethisterone concentrations determined in healthy volunteers reached peak values at about 1 hour after administering a norethisterone-containing oral contraceptive preparation. The maximum values achieved in saliva (775–1430 pmol/l) were only approximately 3% of those observed in plasma. Since salivary norethisterone concentrations reflected those in plasma, they may be useful in fertility control programmes and pharmacokinetic studies.     

A solid-phase radioimmunoassay for plasma progesterone

A detailed procedure is presented for the assay of plasma progesterone. The routine assay is based on the use of antiserum which is covalently linked to microcrystalline cellulose, the double-antibody method being used as a reference separation system. This procedure gives high precision accompanied by small and acceptable losses of antiserum titre but without loss of sensitivity when compared with the double-antibody method. Ethanol is first added to the plasma (10vol. of plasma+1vol. of ethanol) after which a single extraction with light petroleum yields a constant recovery [92.4+/-1.2 (s.d.)% of added [(3)H]progesterone] and obviates the need for tracer recoveries on each sample being assayed. Distortions of the response curve owing to solvent residues have been almost eliminated. The assay can measure progesterone at all stages of the menstrual cycle when volumes of 200mul of plasma are used and this permits the detection of the periovulatory rise at its inception. Detailed specificity studies are presented for the assay end point itself and these are related to the responses to be expected in extracts of plasma. Progesterone-like activity was found in urine and a fourfold increase in excretion rates was observed between the follicular and luteal phase of the normal menstrual cycle.     

Development of a sensitive enzymeimmunoassay for oxytocin determination in bovine plasma

A highly sensitive and specific second antibody enzymeimmunoassay (EIA) on microtiterplates for oxytocin determination in bovine plasma using the biotin–streptavidin amplification system was developed. Biotin was coupled to oxytocin and used to bridge between streptavidin-peroxidase and the immobilized oxytocin antiserum in the competitive assay. The assay was carried out directly in 200 μl of bovine plasma. Oxytocin standards prepared in hormone-free plasma were used. The sensitivity of the assay was 0.25 pg/well which corresponded to 1.25 pg/ml plasma; the 50% relative binding was seen at 2.8 pg/well. Plasma volumes for the assay ranging from 50 to 200 μl did not influence the shape of the oxytocin standard curve; however a distinct drop in the OD₄₅₀ was observed with higher plasma volumes. The oxytocin antiserum used in the assay showed no significant cross-reaction with other octapeptides tested. The assay was compared with a radioimmunoassay (RIA) procedure employing prior solvent extraction of plasma samples. The oxytocin concentrations assayed by EIA and RIA in plasma samples obtained from four cows before, during and after milking were highly correlated and very similar (r=0.97). Hence the assay developed offers an attractive alternative to the RIA since no prior laborious plasma extraction is needed. Further, the assay has the distinct advantage of being non-radioactive in nature.     

A specific assay for subnanogram concentrations of reserpine in human plasma

A sensitive analytical procedure was developed for the measurement of reserpine in human plasma. The method is based on thin layer chromatography followed by development of a fluorophor with acetic acid vapor. The thin layer plates were scanned with a Vitatron “flying spot” densitometer. Use of an internal standard minimized errors in quantitative spotting. Plasma levels were measured in healthy subjects after single oral and intramuscular doses of 1 mg of reserpine.     

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).     

A rapid specific radioimmunoassay for unconjugated estriol in plasma.

A rapid, non-chromatographic radioimmunossaay for unconjugated estriol in pregnancy plasma has been developed which utilizes a commonly available antiestrogen antisera. Estradiol-17beta and estrone demonstrate 135% relative cross-reactivity with our antiserum, as compared with 100% for estriol. Specificity is achieved by purification of estriol with solvent partitioning using benzene: petroleum ether (1:1). The results obtained using this method are similar to a radioimmunoassay utilizing a highly specific, but commercially unavailable, antiestriol antiserum. The method is precise, with coefficients of variation ranging from 3.0 to 8.2%.     

A sensitive enzymeimmunoassay with a fluorimetric end-point for the determination of testosterone in female plasma and saliva

A fluorimetric enzymeimmunoassay has been developed having the sensitivity (50O fg/assay tube) required for determining testosterone concentrations in female plasma and saliva samples. The assay featured a solid-phase antiserum raised against an llα-hydroxytestosterone-11-hemisuccinate bovine serum albumin conjugate, an llα-hydroxytestosterone-11-hemisuccinate horseradish peroxidase conjugate as the “enzyme label” and p-hydroxyphenylacetic acid as the substrate for the development of fluorescence. Specificity was ensured by “extracting” testosterone from samples with a solid-phase anti testosterone-3-¦O-carboxymethyl¦-oxime serum. The assay was shown to satisfy accepted validation criteria providing results in good agreement with routine radioimmunoassay procedures in both plasma (r > 0.98, n = 28) and saliva (r > 0.99, n = 28). In saliva samples collected at 2 hourly intervals by normal healthy women (n = 5) testosterone concentrations showed a well defined circadian rhythm: the mean testosterone concentration in early morning samples (174 pmol/litre) fell by 83% in late evening collections. In healthy female volunteers (n = 7), mean salivary testosterone concentrations in samples collected daily throughout one complete cycle ranged from 5O to 218 pmol/litre. Following dexamethasone administration testosterone concentrations in plasma fell by approximately 50% and salivary concentrations were undetectable after one hour. This enzymeimmunoassay may be useful in studies of female infertility.     

A rapid and precise method for measurement of physiological variations of human plasma progesterone

A practical and precise radioimmunoassay for plasma progesterone (P) is described using a highly specific antiserum produced in the sheep immunized against progesterone-11α-succinyl-BSA. Purification of the extracts was achieved by a rapid efficient chromatography on small Sephadex LH-20 columns whereby a dye is included to monitor the P fraction. Recovery of ³H-P after extraction and chromatography was 63 ± 7.9 (S.D.), The sensitivity of the assay was 10 pg. The intra and inter-assay coefficients of variation were 7.7 and 15.1% respectively. Mean values of plasma P were 9.5 ± 6.5 (S.D.) in males and 8.5 ± 6.6 ng/100ml in females during follicular phase of the menstrual cycle. There was no significant difference between the two groups. Plasma samples obtained during luteal phase (day 17–26) varied from 119 to 1697 ng/100ml. In all instances, non-chromatographed samples yielded consistently higher values, thus emphasizing the need for adequate purification if precise P values are needed for physiological studies.