Direct enzymeimmunoassay of progesterone in bovine milk

Diagnosis of pregnancy by radioimmunoassay of a pregnancy-specific protein in the plasma of dairy cows

The accuracy and efficiency of progesterone (P4) and bovine pregnancy-specific protein B (bPSPB) radioimmunoassays (RIA) in detecting pregnant and nonpregnant dairy cows were compared at different stages of pregnancy. The study included 145 French Friesian heifers and cows from a single herd. A total of 175 artificial insemination (A.I.) and blood sampling procedures were performed. Animals were bled 24 d post AI for P4 RIA. They were bled at 24, 26, 30 to 35, and 70 +/- 9 after AI for bPSPB RIA. Females were declared nonpregnant when plasma P4 concentrations were lower than 1.5 ng/ml. With the bPSPB RIA, cows were nonpregnant when at least one of the B Bo x 100 replicates was higher than 95% in the RIA. When compared with palpations per rectum at 70 d, the accuracy of positive diagnoses (no. positive and pregnant/no. positive diagnoses) by P4 RIA at Day 24 was 67.2% (82 122 ). The accuracy of negative diagnoses was 98% (52 53 ). Accuracy of positive diagnoses by bPSPB RIA increased with gestation age (P<0.05) from 86.2% (50 58 ) on Day 24 to 98.8% (83 84 ) at time of palpation per rectum. Accuracy of negative diagnoses increased (P< 0.001) from Day 24 (71.8%; 84 117 ) to Days 30 to 35 (100%, 83 83 ). Efficiency in detecting nonpregnant females was much higher (P < 0.001) with the bPSPB RIA on Days 30 to 35 (90.2%; 83 92 ) than with the P4 RIA on Day 24 (56.5%, 52 92 ). It is concluded that 30 days after AI, the bPSPB RIA is an efficient test both for pregnancy prediction and detection of nonpregnant dairy cows.

A direct antigen heterologous enzyme immunoassay for measuring progesterone in serum without using displacer

An antigen heterologous enzyme-linked immunosorbent assay (ELISA) for directly measuring progesterone in serum is described. Six combinations of antigens and enzyme conjugates were tested; the enzyme conjugate 17-alphaOH-progesterone-3-O-carboxymethyloxime-alkalinephosphatase (17-alphaOH-P-3-CMO-ALP) and the immunogen progesterone-3-carboxymethyloxime-bovine serum albumin (P-3-CMO-BSA) were found to be best. Fifty microliters of standard or serum sample and 100 microL of the 17-alphaOH-P-3-CMO-ALP enzyme conjugate were added to the antibody coated wells, and incubated for 1 h at 37 degrees C. Bound enzyme activity was measured by using p-nitrophenyl phosphate as substrate. The sensitivity of the assay was 0.11 ng/mL, and intra- and inter-assay CVs ranged from 5.1% to 9.6%. The analytical recoveries were 97-105%. The serum progesterone values obtained by this method correlated well with those obtained by radioimmunoassay; r=0.97 (n=44). Moreover, in this ELISA no displacing agent was used or special means was required to displace progesterone from corticosteroid binding globulin (CBG). Serum progesterone concentrations of subjects, with histories of recurrent spontaneous abortions were also measured, and correlated well with clinical history.

Progesterone in milk: a simple experiment illustrating the estrous cycle and enzyme immunoassay

Experiments designed for students in reproductive physiology are rare. Here, we describe a simple experiment concerning a physiological aspect of the reproductive system. Milk samples are obtained from cows in estrus, in midcycle, 21 days after insemination, and in gestation. With these samples, the gestation or estrous stage is determined according to the progesterone level in milk that is measured using enzyme immunoassay. This experiment can therefore be used to demonstrate assay techniques and to illustrate the variations in progesterone concentrations during an estrous cycle and gestation. This exercise should be given after the reproduction section of the animal physiology course so that students can apply their knowledge concerning hormonal profiles during an estrous cycle.

The Development of a Sensitive Enzymeimmunoassay for the Determination of Estrone and Estradiol-17.BETA. in Bovine Blood Plasma based on the Same Homologous Combination with Antiserum and Steroid-Enzyme Conjugate

The development of a sensitive enzymeimmunoassay (EIA) for the determination of estrone (E1) and estradiol-17beta (E2 beta) in bovine plasma is described. The assay is a homologous double-antibody EIA with E2beta 17hemisuccinate (HS) as hapten for the immunoreactive reagent. The antiserum was raised against E2beta 17HS bovine serum albumin conjugate in the rabbit, and E2beta 17HS-horseradish peroxidase was used as steroid-enzyme conjugate. Each estrogen EIA was distinguished only by using the each working standard and sample for the EIA. Bovine plasma E1 and E2beta were extracted and purified before EIA. The antiserum was used at 1:1,750,000 dilutions for EIA. Estrone and E2beta showed high cross-reactivity with the antiserum (E1: 350.7%, E2beta:100%). The sensitivities were <0.03 pg/well for E1 and <0.12 pg/well for E2beta. Recovery rates of E1 and E2beta added to bovine blood plasma were 94.5% and 93.9%, respectively. The precision for EIA of estrogens was below 9.7%. The profiles of either estrogen as determined by EIA corresponded closely well with follicle dynamics in the cow during the estrous cycles and with placental function in pregnant animals. In conclusion, our new EIA can be applied with sufficient sensitivities, recovery and precision for the routine analysis of E1 and E2beta concentrations in bovine plasma.

A competitive enzyme immunoassay for the direct determination of mometasone furoate (SCH 32088) in human plasma

Mometasone furoate (SCH 32088) is a synthetic corticosteroid which has a topical anti-inflammatory activity with a minimal potential for suppressing hypothalamic-pituitary-adrenocortical (HPA) axis. A sensitive competitive enzyme immunoassay (EIA) for measuring SCH 32088 in unextracted human plasma has been developed. The 3-(O-carboxymethyl)oxime (CMO) of SCH 32088 was synthesized and conjugated with bovine thyroglobulin, and the product was used for the production of antibodies in rabbits. SCH 32088-3-CMO was also conjugated with horseradish peroxidase, which was used as the tracer. The EIA thus developed can detect 1 pg SCH 32088 per assay or 25 pg per ml of human plasma. It can reliably quantitate SCH 32088 in human plasma from 50 pg ml-1 to 2.5 ng ml-1 with good linearity, accuracy and precision. The assay can be extended to measure SCH 32088 in plasma of laboratory animals. The availability of this sensitive assay makes it possible to evaluate the pharmacokinetics and toxicokinetics of SCH 32088 in laboratory animals and man.

Pregnancy diagnosis in dairy goats and cows using progesterone assay kits

Early pregnancy diagnosis in dairy goats and cows was studied using enzyme immunoassays (EIA) to measure progesterone concentrations in whole milk samples collected approximately 3 weeks after mating. Two qualitative on-farm assay kits and 2 quantitative assay kits, all designed for use in the dairy cow, were tested for their accuracy with goats milk samples. Accuracy of diagnosis of goat pregnancy ranged from 83 to 88%, and of non-pregnancy from 80 to 100%. Pregnancy diagnosis with samples of cows milk using 2 quantitative kits gave accuracies of 66 to 68% for pregnancy, and 90 to 91% for non-pregnancy. Possible causes of error in the early diagnosis of pregnancy with milk samples are discussed.

Development of a simple, direct, microtitre plate enzymeimmunoassay (EIA) for progesterone determination in whole milk of buffaloes

A method of estimating progesterone in buffalo whole milk by EIA using progesterone 6 beta-OH-hemisuccinate-horseradish peroxidase as the enzyme label and an antiserum raised against progesterone-7 alpha-carboxyethyl-thioether-BSA was developed. The microtitration plates used in the assay were first coated with affinity purified sheep IgG developed against rabbit IgG. The immune reaction was performed by incubating a mixture of 1 microliter of whole milk (diluted to 20 microliters with assay buffer), 100 microliters of enzyme label and 100 microliters of antiserum for 90 min in the dark. After washing the plates, 150 microliters of the substrate solution was added. The mixture was incubated in the dark for 40 min before the reaction was stopped and the optical density was measured at 450 nm. The calibration curve was sensitive in the range 0.8-40 pg/well, corresponding to 0.8-40 ng/ml. Milk samples from cycling buffaloes were tested for progesterone concentration by running parallel EIA and RIA. A good correlation of 0.91 was obtained and the estimated values were similar using both techniques. The method has demonstrated about 10 times greater sensitivity than RIA in buffalo milk.

[Quantitation of plasma progesterone using a commercial immunoassay. Comparison with a specific radioimmunoassay]

Plasma progesterone (P) was determined by enzymeimmunology with commercially available kits. Two kits (Serono and bioMérieux) were studied. The results obtained by either enzymeimmunoassay were compared to reliable and specific radioimmunoassays. The bioMérieux kit was shown to be more appropriate than the Serono kit for plasma P assay except in patients after oral administration of micronized progesterone because of the interference of the high levels of P metabolites.

A comparison of alkaline phosphatase, beta-galactosidase, penicillinase and peroxidase used as labels for progesterone determination in milk by heterologous microtitre plate enzymeimmunoassay

Assays for alkaline phospatase, beta-galactosidase, penicillinase and peroxidase were optimised for quantitation in microtitre plate wells. Their value as labels in microtitre plate enzymeimmunoassay (EIA) for progesterone was assessed following coupling with 11 alpha-hydroxyprogesterone 11-glucuronide using an active ester procedure. Bridge-heterologous antiserum (11 alpha-hydroxyprogesterone 11-hemisuccinate-bovine serum albumin as immunogen) was used to minimize bridge recognition. The limits of detection of the enzymes were in the order penicillinase greater than peroxidase greater than alkaline phosphatase greater than beta-galactosidase. Under appropriate conditions it was possible to achieve greater than 50% displacement of label with 50 pg of progesterone for all four labels.

The influence of heterology, enzyme label and assay conditions on the sensitivity of microtitre plate enzymeimmunoassays for progesterone in milk

Seven antisera raised against 11 alpha-hydroxyprogesterone 11-hemisuccinate (P11-HS) were used in microtitre plate enzymeimmunoassays (EIAs) for progesterone to identify improvements in sensitivity achievable by using various heterologous labels. EIAs using beta-galactosidase linked to P11-HS, 11 alpha-hydroxyprogesterone 11-hemimaleate (P11-HM), 11 alpha-hydroxyprogesterone 11-glucuronide (P11-Glu) or progesterone 3-(o-carboxymethyl) oxime (P3-CMO) were compared. Loss of sensitivity through bridge recognition was least evident using the P11-Glu derivative. The same seven antisera were used to evaluate assay sensitivity using beta-galactosidase, alkaline phosphatase, penicillinase and peroxidase linked to P11-HS or P11-Glu as label. Consistent improvements were achieved with the heterologous assays in the order penicillinase greater than alkaline phosphatase/peroxidase greater than beta-galactosidase: with penicillinase, sensitivity generally exceeded that of RIA. These data provide evidence for the general efficacy of the combination 11 alpha-hemisuccinate (immunogen bridge) and 11 alpha-glucuronide (label bridge) in reducing bridge recognition. EIA performed at 4 degrees C provided greater sensitivity than at ambient temperature (21 degrees C) or 40 degrees C, however, ambient temperature incubation provided a practical compromise. Equilibrium was not achieved under any of the conditions investigated.

A rapid approach to 11 alpha-hemisuccinylprogesterone synthesis

The synthetic hapten 11 alpha-hemisuccinylprogesterone (11 alpha-hemisuccinyl-pregn-4-ene-3,20-dione), when linked to the appropriate macromolecular carrier, has been used successfully as a solid-phase antigen for progesterone detection in immunoassay. In this study the synthesis of 11 alpha-hemisuccinylprogesterone from 11 alpha-hydroxyprogesterone has been improved by using 4-dimethylaminopyridine (DMAP in refluxing dioxane, a highly nucleophilic polar solvent.

On-farm milk progesterone tests

Results from milk progesterone assays can provide ovarian information, making it possible to monitor the reproductive status of the cow. Rapid, simple, and accurate on-farm milk progesterone tests are commercially available. Procedures for performing milk progesterone tests are specific for each test; however, principles of testing are similar. On-farm tests are designed to determine the relative progesterone concentration ("high" or "low") rather than obtaining a precise concentration. Evaluation of results is based on either a color or agglutination reaction with comparison to known standards. Potential uses of progesterone testing in a reproductive management program are: 1) identifying errors in detection of estrus, 2) predicting time of estrus, 3) assisting in pregnancy diagnosis, 4) differentiating types of ovarian cysts, and 5) evaluating response to endocrine therapy.

An enzyme-linked immunoassay of milk progesterone as a diagnostic aid in embryo transfer programs

The objective of this study was to use an enzyme-linked immunosorbent assay to measure progesterone (P(4)) in donor cows as an indicator of reproductive normality and response to superovulatory treatment. Forty-eight Holstein cows were superovulated, and blood and milk samples were collected four times: 1) at initial follicle stimulating hormone treatment, 2) just prior to administration of prostaglandin F(2)-alpha, 3) at estrus and 4) at the time of embryo recovery, 6 to 7 d after estrus. Cows were inseminated twice during estrus. The P(4) profiles (ng/ml) obtained at the four collections, were, respectively, as follows: blood plasma, 2.4, 2.7, 0.2 and 11.2; defatted milk analyzed by radioimmunoassay, 3.7, 3.8, 0.5 and 14.6; preserved whole milk analyzed by ELISA, 6.3, 7.8, 0.7 and 19.1; frozen whole milk analyzed by ELISA, 9.8, 10.0, 0.8 and 21.1. All four assays resulted in the expected pattern of P(4) values for most cows at the four stages sampled. Approximately 10% of the cows had P(4) concentrations outside of the expected range of values. A majority of these cows were aberrant, based upon behavior and palpation of the reproductive organs. The rapidly available P(4) results from the ELISA were useful in making appropriate decisions regarding management of donor cows.

Characterization of the caprine estrous cycle using enzyme immunoassay for the determination of whole blood progesterone concentration

Eighteen mature female dairy goats were used to determine the feasibility of enzyme immunoassay for the measurement of progesterone in this species. Both quantitative and qualitative enzyme immunoassay kits were used to measure progesterone concentration in unextracted whole blood. Progesterone profiles were similar to those previously reported using either protein-binding or radioimmunoassay as the test. A Pearson's correlation coefficient comparison of our enzyme immunoassay values with radioimmunoassay values gave a correlation coefficient of 0.95. Using the qualitative test, 100% of the samples with high progesterone concentrations had quantitative values greater than 4.00 ng/ml progesterone with a mean of 12.13 ng/ml. Estrus samples had a mean progesterone concentration of 0.70 ng/ml.

A highly sensitive microtitre plate enzyme immunoassay for oestradiol-17 beta

A specific and sensitive solid-phase microtitre plate enzyme-linked immunosorbent assay for oestradiol-17 beta (E2) is described. After coating with an IgG anti-E2 fraction, we used E2-6-carboxymethyl-oxime-beta-galactosidase in a competitive binding assay and revealed the bound activity with a fluorogenic substrate. Two methods for the competitive binding assay were tested: (1) a classical one (method A) defined as a 'two-step competition' because the E2 sample was first incubated alone, and then E2-beta-galactosidase conjugate was added; (2) and a new one (method B) also performed in two steps but in which the E2 sample was evaporated to dryness. The detection limit of method A was 100 pg/ml (9 pg/well). Method B was more sensitive since 1 pg/ml (0.3 pg/well) was statistically different from 0 pg/ml. Specificity was equivalent with both methods while precision was better in B. Thus, this new method may be able to measure very low levels of oestradiol-17 beta in, for example, the blood of domestic mammals.

Comparison of on-farm laboratory milk progesterone assays for identifying errors in detection of estrus and diagnosis of pregnancy

A field study was conducted in 10 commercial dairy herds to test the efficacy of a rapid enzyme-linked immunosorbent assay to identify errors in detection of estrus and diagnosis of pregnancy. Milk samples were collected at the milking following detection of estrus and on d 21 postinsemination. Progesterone was measured on-farm by an enzyme-linked immunosorbent assay and in the laboratory by radioimmunoassay. Agreement between the two methods of progesterone analysis (n = 820) was 89.8%. There were 93 cows (18.7%) by laboratory analysis and 126 cows (25.4%) by on-farm analysis for which concentration of progesterone in the sample collected at suspected estrus (n = 497) was higher than normal estrual values. Exclusion of these cases increased the overall accuracy of pregnancy diagnosis by 6.8 and 6.4% for laboratory and on-farm methods. Overall agreement between pregnancy diagnosis by milk progesterone at d 21 postinsemination and diagnosis by return to estrus or palpation of reproductive organs was 80.5 and 75.8% for laboratory and on-farm methods (75.0% and 69.7% for pregnant cows and 94.5 and 93.9% for nonpregnant cows). These results indicate that an enzyme-linked immunosorbent assay for milk progesterone performed on-farm was equal in accuracy to a laboratory radioimmunoassay for identifying errors in detection of estrus and diagnosis of pregnancy.

A simple procedure for enzyme labelling of progesterone derivatives: application of active esters formed using N,N'-disuccinimidyl carbonate

N,N'-Disuccinimidyl carbonate was used to synthesize N-hydroxysuccinimide esters of 11 alpha-hydroxyprogesterone 11-[1,4-14C]hemisuccinate (P11-HS) and 11 alpha-hydroxyprogesterone 11-glucuronide (P11-Glu) in a one-step procedure at room temperature. Enzyme-labelled progesterone was subsequently formed by reaction of the ester, without purification, with alkaline phosphatase. Labels produced by this simple procedure compared favourably with those formed using an established method of ester synthesis when assessed in enzyme immunoassay (EIA).

Use of enzyme-linked immunosorbent assay for measurement of bovine serum and milk progesterone without extraction

An enzyme immunoassay for progesterone, using horseradish peroxidase as the label, was adapted for direct measurement of progesterone in serum or milk. Values obtained by direct measurement are highly correlated with values measured in extracts and are usable for convenient, rapid, accurate monitoring of the reproductive status of dairy cows. The assay is sensitive (ca. 1 pg), rapidly performed (3.5 h), and allows 92% accuracy in assessment of pregnancy status by direct measurement of progesterone in paired milk samples collected at breeding and 21 d later.

A simple enzyme-linked immunosorbent assay for testosterone

A new, enzyme-linked, immunosorbent assay for testosterone is described. The assay uses horseradish peroxidase coupled to testosterone as the tracer and offers the same sensitivity and reliability but greater convenience than radioimmunoassay. The assay is also simpler and more rapidly completed than previously described assays for testosterone.

Steroid determination in milk by enzyme immunoassay (EIA)

A simple and sensitive enzyme immunoassay for progesterone using a homologous system was developed covering the range of 30-3000 fmol/test tube (9.4-944 pg) and applied to extracts from milk fat and bovine serum. By changing the incubation procedure the sensitivity of the assay was increased to measure milk from cows directly without extraction. The influence of milk fat is tolerable and does not falsify physiological results concerning corpus luteum activity or inactivity. The EIA can also be used to follow the change of progesterone under physiological, pathological and therapeutic conditions in samples of human blood and saliva after extraction and in serum directly.

Development of a direct enzyme immunoassay of milk progesterone and its application to pregnancy diagnosis in cows

The purposes of this study were to develop an enzyme immunoassay (EIA) for determination of progesterone in unextracted whole milk and to apply it to pregnancy diagnosis. Paper fibers covalently coupled to antibody specifically and competitively bound 3H-progesterone and 11 alpha-hydroxyprogesterone hemisuccinate-horseradish peroxidase and were stable for 9 mo at -20 degrees C. The sensitivity, recovery, precision, and cross reactivity of the EIA and a radioimmunoassay (RIA) of milk progesterone were evaluated, and showed that this EIA was comparable to the RIA. Milk samples were collected once daily for one estrous cycle from ten lactating Holstein cows and the progesterone levels were determined by RIA. Milk progesterone in 70 samples measured by EIA were highly correlated (r = 0.90) with the values of RIA for the same samples. Milk samples for pregnancy diagnosis by EIA of milk progesterone were obtained daily from days 20 to 24 after 115 artificial inseminations of 85 lactating Holstein cows. Pregnancy diagnosis by EIA was confirmed by rectal palpation at 30 to 60 days after insemination or return to estrus. The accuracy based on single, two, three, four, and five consecutive samples was from 67.2 to 80.0%, 77.3 to 84.0%, 79.2 to 87.5%, 82.0 to 85.4%, and 85.4%, respectively, for pregnancy diagnosis; and from 95.0 to 98.3% for nonpregnancy.

Use of milk progesterone enzyme immunoassay for early pregnancy diagnosis in cows

An enzyme immunoassay using beta-galactosidase as the tracer was applied to determine milk progesterone level in cows. The novel method was reliable and practicable and required only a spectrophotometer and a centrifuge as major equipment. The milk progesterone enzyme immunoassay successfully diagnosed early pregnancy in cows. Milk samples were collected from 268 Holstein-Friesian cows in commercial dairy herds on 20, 21 or 22 days(usually 21 days) after insemination. Progesterone level in skim milk higher than 1.0 ng/ml indi-cated pregnancy. Pregnancy was confirmed by rectal palpation on 60 to 120 days after insemination. The accuracy of the milk progesterone test was 60.0 % (132 220 ) for a positive diagnosis and 100 % (48 48 ) for a negative result. A high incidence of embryonic death, 27.9 % (51 183 ), may have reduced accuracy for a positive test result. The enzyme immunoassay may be an alternative to radioimmunoassay in milk progesterone analysis for pregnancy diagnosis.