A rapid, solid-phase microtitre plate enzyme immunoassay (EIA) for progesterone is described using progesterone 3-O-carboxymethyloxime-horseradish peroxidase as the label and an antiserum raised in rabbits to a progesterone 11 alpha-hemisuccinyl-bovine serum albumin immunogen. A competitive reaction was used with a reaction time of 2 h. Antibody-bound and free steroid were separated in a simple washing step of the antibody-adsorbed well surface. 2,2'-Azino-di-(3-ethylbenzthiazoline sulphonic acid) diammonium salt was used as the substrate with a reaction time of 1 h. A lower limit of sensitivity of 0.25 pg/well was obtained with the response being linear (logit/log) through 1000 pg/well. Results obtained by EIA and radioimmunoassay in several species gave excellent agreement (r = 0.98). This assay system allows accurate determination of progesterone in plasma with good specificity, precision and accuracy, and is suitable for the rapid assessment of luteal function and reproductive status in both clinical and research situations in a wide variety of species.

Paired daily blood and urine samples were collected from 10 apparently healthy premenopausal women to compare the hormone profiles of estradiol (E2) and progesterone in serum with those of estrone conjugates (E1Conj) and pregnanediol-3-glucuronide (PdG) in urine. Serum hormones were measured by radioimmunoassay (RIA) kits, whereas the urinary steroid metabolites were assessed by both RIA and enzyme immunoassay (EIA). RIA and EIA values for urinary E1Conj and PdG were not different, and both methods produced urinary profiles that paralleled the profile of the parent steroid in serum. However, the simplicity, flexibility, and economy of EIA will make this method more widely applicable. Mean E1Conj values lagged behind concentrations of serum E2 by one day or less, whereas daily urinary PdG profiles lagged behind serum progesterone by one to two days. Mean urinary profiles of E1Conj were similar whether or not creatinine was used to adjust for urine volume; however, creatinine indexing was beneficial when urinary profiles in individual cycles were compared with changes of serum E2.

Ovarian follicular dynamics were determined in adult llamas by ultrasonography and palpation per rectum and hormone analysis (estradiol-17 beta and estrogen conjugates) of plasma and urine. The relationship of gonadotropin secretion to follicular development was determined by the analysis of plasma FSH and LH concentrations. Progesterone analysis of plasma was used to verify or deny the presence of CL. Final follicular development (from 3 mm) averaged 4.8 days, while the duration of the mature follicle (8-12 mm) averaged 5.0 days; regression of the follicle occurred over about 4 days. The development of a subsequent dominant follicle usually began within 2-3 days after onset of regression of the dominant follicle. While several follicles were present at the time of the demise of the dominant follicle, only one follicle continued to develop. The interval between ovarian follicle waves averaged 11.1 days. Dominant follicle activity alternated between ovaries in 81% of the cycles. The occurrence of dominant follicles was evenly distributed between ovaries. While plasma estradiol and estrogen conjugate concentrations were positively associated (p less than 0.05) with follicular activity, urinary estrogen conjugate concentrations best reflected ovarian follicular dynamics (p less than 0.001). Daily FSH concentrations in plasma were not correlated with follicular activity. LH concentrations in plasma were low in all animals throughout the study, indicating estrogen from developing ovarian follicles does not induce the release of LH. Progesterone values were low during the study, indicating that the llama does not spontaneously ovulate, at least under the conditions of this study. In summary, llamas have overlapping ovarian follicle waves that occur at about 11-day intervals.(ABSTRACT TRUNCATED AT 250 WORDS)

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