Development of third-generation immunochemiluminometric assays of follitropin and lutropin and clinical application in determining pediatric reference ranges

We developed dioxatane-based immunochemiluminometric assays (ICMAs) for lutropin (LH) and follitropin (FSH), using monoclonal antibodies. These ICMAs have a minimal detectable dose (analytical sensitivity) of 0.01 IU/L, extending the lower limit of sensitivity 10-fold (from 0.10 IU/L) when compared with immunoradiometric assays (IRMA) (second generation), and thus provide a true third-generation assay. Daytime FSH and LH concentrations were measured in 236 boys and 195 girls. Unlike the previous assays, all the samples had detectable concentrations of LH and FSH. In agreement with results from earlier methods, the present results indicate that for both sexes mean FSH and LH concentrations are relatively high during the early months of life, fall to baseline prepubertal concentrations by 12-18 months, and remain low until the onset of puberty. During puberty, the mean concentrations of FSH and LH increase significantly in both girls and boys with each stage of puberty, but there is considerable overlap between stages. These third-generation FSH and LH ICMAs reliably separate daytime plasma FSH and LH concentrations of prepubertal children from those of sexually mature children, and therefore can more reliably distinguish between the major causes of precocious puberty (e.g., gonadotropin dependent and independent). Our LH assay is also useful in monitoring the gonadotropin-releasing hormone therapy of patients with gonadotropin-dependent precocious puberty.

Metabolic clearance and production rates of human luteinizing hormone in pre- and postmenopausal women

Metabolic clearance rates and production rates of human luteinizing hormone (HLH) were determined in pre- and postmenopausal women by the constant infusion technique. Highly purified HLH-(131)I was infused into the fasting subjects at a constant rate. Serial plasma samples were obtained and the radioactive hormone was precipitated by a double antibody technique. Plasma HLH-(131)I levels reached equilibrium by 4 hr after the infusion started. Metabolic clearance rates were: 24.4 +/- 1.8 (mean +/- SE) ml/min in five normal premenopausal women; 23.3 +/- 1.1 ml/min in five normal women taking norethinodrel and mestranol; and 25.6 +/- 4.1 ml/min in four postmenopausal women. Endogenous plasma HLH levels measured in the same subjects by radioimmunoassay immediately before infusion were 32.0 +/- 9.6 mU/ml in the normal women, 16.8 +/- 3.2 mU/ml in the women on oral contraceptives, and 99.2 +/- 23.2 mU/ml in the postmenopausal women. The corresponding HLH production rates were: 734 +/- 170 mU/min in the normal women: 387 +/- 86 mU/min in the women on norethinodrel and mestranol; and 2400 +/- 410 mU/min in the postmenopausal women. The metabolic clearance rate did not change after ovariectomy in one women, but the production rate rose from 583 to 1420 mU/min. Based on previously reported bioassay values for pituitary content and urinary excretion of HLH, the estimated turnover of HLH in the pituitary is about once per day and less than 5% of the total HLH produced appears in the urine in a biologically active form.

Endocrine/metabolic syndromes of cancer

In addition to producing symptoms directly by their mass or invasion of tissues, cancers may also make themselves evident by the secretion of cytokines, protein hormones, or hormone precursors, which in turn, results in recognizable clinical syndromes. This article reviews the endocrine syndromes of cancer, their pathophysiologic basis, and the means of diagnosis. Many of these protein hormones appear to be produced in small amounts by normal tissues where they act in paracrine fashion as cytokines. Furthermore, neoplastic transformation is associated with continued, or often dramatically amplified, production of paracrine substances, permitting them to circulate in the blood and to act as hormones. Thus, classical definitions of cytokines and hormones become blurred. In this context, so-called "ectopic" cancer production is not ectopic, but rather a modification of normal cell function. The majority of the endocrine syndromes of cancer are caused by cancer production of these cytokines or hormones. Except for cancers originating in the adrenals or gonads, cancers do not synthesize steroids and secrete them, although very rarely a cancer may metabolize a normal steroid precursor to produce a biologically active steroid.

Identification of a CG/LH binding site in two strains of Mycobacterium vaccae

We have previously reported the presence of a chorionic gonadotropin-like (CG-like) protein in the bacterium Xanthomonas maltophilia (X. maltophilia). We have also shown that X. maltophilia possesses a unique binding site for the native ligand and hCG, but not for human luteinizing hormone (hLH), and that binding of the native ligand or hCG to the receptor causes changes in the growth rates of culturing X. maltophilia. In this study we have characterized a CG/LH binding site in two strains of Mycobacterium vaccae. The binding site is specific for hCG and hLH, and Scatchard analysis reveals a biphasic, high affinity binding pattern. This is the second identified bacterial species to possess a CG-specific binding site.

Contrasts in the gonadotropin-releasing hormone dose-response relationships for luteinizing hormone, follicle-stimulating hormone and alpha-subunit release in young versus older men: appraisal with high-specificity immunoradiometric assay and deconvolution analysis

The secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) is regulated by gonadotropin-releasing hormone (GnRH). As men age, mean serum concentrations of immunoreactive gonadotropic hormones tend to increase, while serum testosterone concentrations tend to decline. To evaluate age-related changes in gonadotroph cell function, we have assessed the dose-dependent secretory responses of immunoreactive LH, FSH and alpha-subunit to saline versus five doses of GnRH in older and young men. Ten older men, mean age 66 years (range 61-78), and nine young men, mean age 26 years (range 22-30), received iv bolus injections of GnRH (range 10-100 micrograms) in randomized order every 2 h, except that the 100-microgram dose was always given last. Blood samples for immunoradiometric assays of serum LH, FSH and alpha-subunit concentrations were obtained every 10 min for a total of 12 h, which included a 2-h preinjection baseline. Deconvolution analysis was performed to estimate gonadotropin and alpha-subunit secretory burst mass, amplitude and duration, as well as endogenous LH, FSH and alpha-subunit half-lives. The mean (+/- SEM) baseline 2-h serum FSH (IU/I) concentration was higher in older than younger men (5.9 +/- 0.8 vs 3.8 +/- 0.5, p < 0.05). The mean 2-h serum LH concentrations after GnRH were significantly higher than corresponding values in young men at GnRH doses of 25, 50 and 75 micrograms, and in the case of FSH at GnRH doses of 10 and 25 micrograms. Non-linear curve-fitting of these dose-response relationships revealed that the calculated maximal mean 2-h serum LH concentration response (IU/l) was higher in older than young men following GnRH stimulation: 15.4 (13.5-16.2) vs 10.8 (8.7-12.1) (95% confidence interval). The maximal mean 2-h serum FSH concentration response (IU/l) was also significantly higher in older men: 11.9 (10.2-13.1) versus 8.6 (7.2-9.6). Maximal alpha-subunit responses (microgram/l) were similarly increased in the older cohort: 1.16 (0.99-1.25) vs 0.83 (0.71-0.91). The incremental LH (p < 0.05) and FSH (p < 0.01) secretory burst mass from 10 to 25 micrograms GnRH was significantly greater in older than younger men. The LH and FSH half-lives and second component alpha-subunit half-lives were similar in older and young men. In addition, secretory burst durations were invariant of age. In contrast, by non-linear curve-fitting, the calculated mass of LH secreted was higher in older men at 13.5 (11.8-15) vs 10.6 (9.2-11.7) IU/l of distribution volume (p < 0.05) for the maximal absolute mass and 11.3 (9.5-12.7) vs 7.4 (6.0-8.4) IU/l (p < 0.05) for the maximal incremental mass of LH secreted after GnRH. The estimated maximal mass of FSH secreted after GnRH also was higher in older men: 4.6 (3.4-5.5) vs 3.2 (2.9-3.4) IU/l (p < 0.01). Finally, calculated maximal GnRH-stimulated alpha-subunit secretory burst mass was statistically greater in older individuals: 2.3 (1.8-2.5) vs 1.6 (1.4-1.8) micrograms/l. In contrast, half-maximally effective GnRH doses were not different in the two age groups. We conclude that older men show significantly increased maximal and incremental gonadotropin release due to amplified secretory burst mass in response to escalating doses of GnRH with no evident differences in LH, FSH, or alpha-subunit half-lives or secretory burst durations. Increased gonadotroph responsiveness may be due to diminished gonadal hormone negative feedback or primary alterations in the hypothalamo-pituitary unit with aging.

Complete sequence of the gene encoding a chorionic gonadotropin-like protein from Xanthomonas maltophilia

Our laboratory has previously reported that: (i) Xanthomonas maltophilia (Xm) produces a protein which has immunological resemblance to the beta-subunit of human chorionic gonadotropin (hCG) and (ii) possesses a high-affinity receptor which binds holo hCG, and the endogenous ligand, Xm chorionic gonadotropin (xCG), but does not bind human luteinizing hormone (hLH). We have also previously published a 492-bp partial nucleotide sequence of the gene (xcg) coding for xCG. We report herein the entire xcg sequence of 1362 bp, which codes for a 48-kDa protein. This sequence confirmed the 492-bp sequence, as well as two partial amino acid (aa) sequences which we have previously reported. The sequence has a region which is homologous to aa 56-139 of the beta-subunit of hCG, and a second region homologous to the C-terminal tail of hCG. This is the first report of a prokaryotic gene homologous to the hCG beta-subunit-encoding gene.

Characterization and purification of the chorionic gonadotropin-like protein binding site in Candida albicans

Recent studies from our laboratory have shown that human chorionic gonadotropin (hCG), human luteinizing hormone (hLH), and CG-like proteins from Xanthomonas maltophilia (xCG) and Candida albicans (CaCGLP) induce Candida albicans transition from blastospores to hyphal forms. Xanthomonas maltophilia CG-like protein (xCG), hCG, and hLH also bind to Candida albicans blastospores with a high-affinity nM Kd, indicating that these substances can control Candida albicans pathogenicity. The work reported herein describes the purification of the binding site for these CG-like proteins from Candida albicans. The purification developed involved alcohol extraction followed by affinity chromatography. The product obtained was a protein of 64-69 kDa, as analyzed by sodium dodecyl sulfate-polyacrylamide electrophoresis (SDS-PAGE), Western blot and Sephadex G-100 column chromatography. This binding site reacted in a Western blot with both 125I-hCG and 125I-CaCGLP. Purified CaCGLP was able to displace specifically 125I-hCG bound to Candida albicans blastospores. Scatchard plot analysis showed that the Kd of this reaction was of high affinity in the nM range, and also indicated the presence of one single binding site. These results lead us to conclude: 1) Candida albicans possesses a binding site which is able to bind hCG, hLH and CG-like proteins from Xanthomonas maltophilia and Candida albicans; 2) This binding site is a hydrophobic protein of approximately 64 kDa and; 3) We postulate that CaCGLP is the natural ligand for this binding site and this system is used to control Candida albicans transition and, therefore, pathogenicity.

The presence of a human chorionic gonadotropin-like protein and its binding site in Saccharomyces cerevisiae

In this study, we characterize from Saccharomyces cerevisiae: 1) a protein that has immunological similarities to human chorionic gonadotropin (hCG), and 2) a binding site for this hCG-like protein which also binds hCG and human luteinizing hormone (hLH). Saccharomyces cerevisiae chorionic gonadotropin-like protein (ScCGLP) was purified in several steps. This protein when analyzed by SDS-PAGE, under nondenaturing conditions, produced two bands, one at 110-kDa, and another at 57.5-kDa. Under denaturing conditions, only the 57.5-kDa band appeared. This 57.5-kDa band also reacted in a Western blot, using a polyclonal antibody directed against hCG. Purified ScCGLP reacted in the following hCG immunoassays: 1) polyclonal rabbit anti-hCG equilibrium assay, 2) carboxyl-tail hCG equilibrium assay, 3) two equilibrium assays using monoclonal antibodies, and 4) free alpha-chain subunit equilibrium assay using a monoclonal antibody. Characterization of hCG/hLH binding sites in Saccharomyces cerevisiae was performed, and the ability of the ScCGLP to displace I125-hCG was also shown. Human CG and hLH were able to compete for I125-hCG binding to Saccharomyces cerevisiae blastospores (Kds of approximately 10(-8) M), while ScCGLP competed with higher affinity (Kd = 9.41 x 10(-10) M). The hCG-like immunoactivity was also present in Saccharomyces growth media, as well as in all brands of commercial beer studied.

Osteoporosis: pathophysiology, prevention, diagnosis, and treatment

Bone is a living tissue; throughout life, new bone formation coexists with bone resorption. Although a large number of hormones and cytokines modulate osteoblast and osteoclast function, osteoporosis results from any disorder in which bone formation becomes uncoupled from bone resorption. Many disorders are associated with the uncoupling of bone formation and resorption. The most common is loss of gonadal steroid action on bone, as occurs in menopause or in male and female hypogonadism not associated with menopause. Other relatively common causes include primary hyperparathyroidism and endogenous or exogenous hypercortisolism and thyrotoxicosis. A large number of other, less frequent disorders also cause osteoporosis. Treatment of osteoporosis consists first of removing the cause if possible, for example, abolishing hypercortisolism, thyrotoxicosis, or hyperparathyroidism. In menopausal women or hypogonadal men or women, replacement of estrogens or androgens represents effective therapy. Estrogens and androgens given to hypogonadal subjects strikingly reduce bone resorption. For patients with established osteoporosis who either cannot take gonadal steroids or who are not hypogonadal, calcitonin decreases bone resorption and may stabilize bone mass. Estrogen replacement and calcitonin are approved by the Food and Drug Administration for treatment of osteoporosis. Experimental therapies presently include 1,25-dihydroxyvitamin D (calcitriol), bisphosphonates in intermittent treatment regimes, and fluoride in lower dosages than were used in previous studies. The use of fluoride is controversial, and to some extent it has fallen into disrepute. Effective use of any treatment is predicated on understanding the pathophysiology in any particular disease setting.

Development of third-generation immunochemiluminometric assays of follitropin and lutropin and clinical application in determining pediatric reference ranges

We developed dioxatane-based immunochemiluminometric assays (ICMAs) for lutropin (LH) and follitropin (FSH), using monoclonal antibodies. These ICMAs have a minimal detectable dose (analytical sensitivity) of 0.01 IU/L, extending the lower limit of sensitivity 10-fold (from 0.10 IU/L) when compared with immunoradiometric assays (IRMA) (second generation), and thus provide a true third-generation assay. Daytime FSH and LH concentrations were measured in 236 boys and 195 girls. Unlike the previous assays, all the samples had detectable concentrations of LH and FSH. In agreement with results from earlier methods, the present results indicate that for both sexes mean FSH and LH concentrations are relatively high during the early months of life, fall to baseline prepubertal concentrations by 12-18 months, and remain low until the onset of puberty. During puberty, the mean concentrations of FSH and LH increase significantly in both girls and boys with each stage of puberty, but there is considerable overlap between stages. These third-generation FSH and LH ICMAs reliably separate daytime plasma FSH and LH concentrations of prepubertal children from those of sexually mature children, and therefore can more reliably distinguish between the major causes of precocious puberty (e.g., gonadotropin dependent and independent). Our LH assay is also useful in monitoring the gonadotropin-releasing hormone therapy of patients with gonadotropin-dependent precocious puberty.

Estradiol stimulates cortisol production by adrenal cells in estrogen-dependent primary adrenocortical nodular dysplasia

Adrenal glands from a patient with ACTH-independent Cushing's syndrome, whose symptoms worsened during pregnancy and oral contraceptive use, were cultured in different concentrations of estradiol. Estradiol stimulated cortisol secretion in a dose-response manner in the absence of ACTH. Since immunoglobulins G from this patient did not stimulate corticosterone production in a mouse adrenal bioassay, an adrenal-stimulating immunoglobulin is unlikely to be the cause of adrenal hyperfunction in this case. This is the first description of estradiol stimulation of cortisol production by cultured adrenal cells in ACTH-independent Cushing's syndrome.

A bacterial protein has homology with human chorionic gonadotropin (hCG)

Studies from our laboratory have demonstrated the presence of a 48.5 kD cell wall protein in the bacterium, Xanthomonas maltophilia, which immunologically resembles the beta subunit of human chorionic gonadotropin. Primers were designed from the amino acid sequences of enzymatically cleaved peptide fragments of this protein. These primers were used to obtain PCR amplified products, which were subsequently cloned in a PCR11TA cloning vector, and a 492 base pair nucleotide sequence was obtained with a 164 amino acid open reading frame. When this nucleotide sequence was aligned with exon 2 of genes 5 and 6 of the beta hCG gene, a 53% homology was observed. The translated protein sequence had a 35% homology with hCG and a 25% homology with human luteinizing hormone.

Evidence for an autocrine/paracrine function of chorionic gonadotropin in Xanthomonas maltophilia

In the human and all other mammalian systems studied, LH and hCG bind to a common high affinity receptor with equal affinity. We have recently reported that a unique high affinity binding site in Xanthomonas maltophilia preferentially binds hCG and a native CG-like ligand over LH or other glycoprotein hormones. In the current studies, we have analyzed the effect of hCG or the native ligand on culturing Xanthomonas maltophilia. Both the human and native ligand caused a dose-dependent alteration in the pattern of the growth cycle and a change in the morphology of the bacteria during the stationary phase of the growth cycle. The protein concentration reached during the stationary phase was significantly (P < 0.005) higher in cultures supplemented with hCG or the native ligand. When an aliquot of the culture was diluted and plated on Earl's Martin Balanced agar plates, the number of subsequent colonies was increased (P < 0.02) in the fractions supplemented with the ligands. The increased growth was significant (P < 0.05) to the lowest concentration of 50 ng/ml ligand. When grown under partially anaerobic conditions, the effects of hCG were observed earlier in the growth cycle. The active hormones, hCG and native ligand, also changed bacterial morphology. These data indicate that hCG may have an autocrine and/or paracrine function in bacteria.

Xanthoma disseminatum, a rare cause of diabetes insipidus

A 33-yr-old male developed typical symptoms and findings of diabetes insipidus. A computed tomographic scan of the hypothalamus/pituitary was normal, and he was diagnosed as having idiopathic diabetes insipidus. At age 38 yr, he developed two 1- to 2-mm reddish papules on his skin. Biopsy revealed infiltrative histiocytes laden with lipid. Bone scans and bone x-rays showed widespread osteolytic and osteoblastic disease. The disease was diagnosed as a rare disseminated histiocytic disorder, xanthoma disseminatum. A classification of histiocytic disease is presented.

Characterization of a human chorionic gonadotropin-like protein from Candida albicans

Studies from our laboratory have demonstrated that human CG (hCG), human LH, (hLH), and an hCG-like protein extracted from Xanthomonas maltophilia were able to induce Candida albicans transition from the blastospore to the germ tube stage. In the present study, we describe the characterization of an hCG-like material extracted from Candida albicans blastospores (CaCGLP), which is potent in inducing transition and presumably represents the endogenous transition-inducing substance. This material was extracted from Candida albicans blastospores with glacial acetic acid and purified by affinity chromatography using a polyclonal rabbit anti-hCG antibody. The product obtained is a 68-kilodalton single band protein, as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analysis. Under reduced conditions a protein smear is seen. Amino acid analysis showed a predominance of glycine (22%), followed by serine (12%), and glutamate (12%). This protein reacted in the following hCG immunoassays: 1) a polyclonal rabbit anti-hCG equilibrium assay, 2) a carboxyl-tail hCG equilibrium assay, 3) two hCG equilibrium assays using monoclonal antibodies (CG no. 4 and CG no. 9), 4) a free alpha-subunit equilibrium assay using a monoclonal antibody, and 5) an ultrasensitive immunoradiometric assay for hCG which does not cross-react with hLH, nor the free beta-subunit of hCG. The CaCGLP showed no reaction in a specific hLH immunoradiometric assay. When CaCGLP was tested in the transition assay, in the presence of 4% rat serum, it was found that this protein was 100 times more potent than hCG in producing Candida albicans transition. We conclude that Candida albicans produces a protein that has certain tertiary structure similarities to hCG and that this material is able to induce germ tube formation. We postulate that CaCGLP has an autocrine/paracrine effect in Candida albicans as a transition factor to control its own pathogenicity.

Partial nucleotide sequence of the Xanthomonas maltophilia chorionic gonadotropin-like receptor

Xanthomonas maltophilia possesses a unique high-affinity binding site which binds human chorionic gonadotropin (hCG), but not human luteinizing hormone (hLH) or other glycoprotein hormones. We designed primers from the known nucleotide sequence of the human LH/CG receptor, spanning an area extending from transmembrane region 2 to transmembrane region 6. Genomic DNA extracted from Xanthomonas maltophilia was used to obtain a PCR amplified product using the above primers. The primary amplification product was cloned in a pCR11 TA cloning vector, and the partial nucleotide sequence of the gene determined. This determined sequence showed 73% identity with the human, as well as the rat LH/CG receptor. Comparison of the translated protein sequence with the human, rat and porcine receptor protein sequences showed a 52% similarity.

Characterization of the 48.5 kDa chorionic gonadotropin-like protein from Xanthomonas maltophilia

Our laboratory has previously reported the isolation of a 48.5 kDa membrane protein from Xanthomonas maltophilia (ATCC 13637) which immunologically cross-reacts with the beta-subunit of human chorionic gonadotropin (hCG) in both polyclonal and monoclonal radioimmunoassays (RIA) (1). The protein showed no reaction in RIAs for human LH, TSH, or the free alpha subunit of hCG. We have now improved the protein purification procedure and have obtained adequate bacterial protein to characterize the pure protein (designated xCG) in RIAs and also to obtain amino acid composition and partial sequence. We present these data and compare homology to hCG. An RIA for the bacterial protein has also been developed.

Enhanced transdermal delivery of testosterone across nonscrotal skin produces physiological concentrations of testosterone and its metabolites in hypogonadal men

None of the current or experimental androgen treatment modalities for male hypogonadism has been reported to produce physiological concentrations or circadian variations in testosterone (T) and its metabolites, dihydrotestosterone (DHT) and estradiol (E2). This investigation describes a novel transdermal dosage form designed to enhance the delivery of native T across nonscrotal skin. The main objective was to determine whether the nightly application of two experimental transdermal patches to different sites on the body (e.g. back, chest, arms, etc.) would result in normal plasma levels of T, DHT, and E2 for men and mimic the normal circadian variation. Six hypogonadal males (aged 24-66 yr) were studied 4 weeks after stopping T ester treatment. After single application of two patches, T levels increased from a pretreatment baseline of 5.8 +/- 0.94 nmol/L (mean +/- SE; 167 +/- 27 ng/dL) to an average peak concentration of 44.1 +/- 4.8 nmol/L (1273 +/- 138 ng/dL) 5.7 +/- 0.6 h after application and reached a 24-h level of 16.9 +/- 2.9 nmol/L (488 +/- 85 ng/dL). DHT and E2 levels exhibited parallel variations within the normal reference ranges. During 4 weeks of daily evening application to various sites on the torso, the mean delivery of T from two patches was 5.2 +/- 0.1 mg/day (approximately 20% of the patch content), and morning T levels were within the normal limits. On day 28 of treatment, the 24-h plasma profiles of T, DHT, and E2 (obtained with two patches on the back) approximately mimicked the normal circadian variations reported in healthy young men. The time-averaged T level was 21.8 +/- 2.9 nmol/L (629 +/- 84 ng/dL), and the plasma concentration ratios of DHT/T (0.07 +/- 0.01) and E2/T (0.005 +/- 0.001) were within the normal range. SHBG concentrations were not significantly altered over the 4 weeks of treatment. The patches were well tolerated, except for one patient who developed a local reaction to an excipient during the third week of treatment. Two of the patients (one with Klinefelter's syndrome) completed several months of continuous therapy. T, DHT, and E2 have remained in the range of normal, and plasma LH levels in the patient with Klinefelter's syndrome became normal. Subjective improvement in symptoms has continued, and tolerability has been good in both patients. These results indicate that the enhanced transdermal delivery of T across nonscrotal skin is a patient-friendly androgen replacement modality and produces physiological concentrations of T and its metabolites, which are unattainable with other treatment modalities.

Partial characterization of the 30 kD Ig-binding protein from Pseudomonas maltophilia

We have previously demonstrated that Pseudomonas maltophilia (ATCC 13637) possess a 30 kDa cell wall protein which binds various subclasses of IgG's and IgA by their Fc region. The protein was solubilized by papain and purified by affinity chromatography on cyanogen bromide activated sepharose beads conjugated with human IgG. The eluent was electrophoresed on a 12% polyacrylamide gel under denaturing conditions, and the immunoactive bands identified by Western blot analysis, a second gel was stained with Coomassie blue. The affinity purified eluent was electrophoresed on a one-dimensional 15% polyacrylamide gel and stained with Coomassie blue. The protein band of interest was cut. The protein band was then digested in situ with Staphylococcus aureus V-8 protease. The peptide bands were separated by electrophoresis on a second one dimensional 15% polyacrylamide gel and then electroblotted into a polyvinylidine difluoride membrane. The bands were visualized by staining with Coomassie blue, cut out, and sequenced using an automated gas phase sequencer. Minimal amino acid composition was determined in a similar fashion. We have thus obtained partial N-terminal amino acid sequence data from the above method.

ACTH immunoactivity in normal rat tissues: modulation by hypophysectomy and adrenalectomy

This study investigates the effect of pertubation of the normal pituitary-adrenal axis on concentrations of adrenocorticotropin (ACTH)-like immunoactivity in peripheral tissues. We used a polyclonal antibody (West antibody) to measure ACTH-like immunoactivity in glacial acetic acid extracts of five tissues in adult male rats at increasing times (1, 7, 14, and 28 days) after hypophysectomy or adrenalectomy, and in normal control rats. Concentrations of ACTH-like immunoactivity were similar to those previously reported in liver, colon, heart, and small intestine and were not significantly affected by either hypophysectomy or adrenalectomy. While hypophysectomy also had no effect in the kidney, adrenalectomy resulted in a four-fold increase in extractable immunoactivity, first noticeable at seven days (p less than 0.005), but increasing progressively to 28 days (p less than 0.0005). Gel filtration showed that most of the increase in activity in kidneys of adrenalectomized rats corresponded to the 4.5 kD form comprising most of the serum ACTH immunoactivity and suggesting that the activity increase in kidney was largely due to ACTH derived from blood.

A bacterial binding site which binds human chorionic gonadotropin but not human luteinizing hormone

Exposed sites on Pseudomonas maltophilia (ATC #1637), which bind both human chorionic gonadotropin (hCG) and a native hCG-like ligand with equal high affinity, are described. This high-affinity binding site (Kd = 1.3 x 10(-10) binds hCG, but does not bind human luteinizing hormone (hLH), nor related human glycoprotein hormones, thyrotropin, and follicle stimulating hormone. A lower affinity, 2.3 x 10(-9), is also described which binds hLH and hCG equally well. This is the first description of a high-affinity binding site in nature, which distinguishes hCG from hLH.

Stimulation of Candida albicans transition by human chorionic gonadotrophin and a bacterial protein

Candida albicans, a dimorphic fungus, is involved commonly in human infections with the mycelium form more associated with pathogenicity. The influence of various hormones and a bacterial protein on the transition from blastospore to mycelium was assessed. Human luteinizing hormone (hLH), chorionic gonadotrophin (hCG), and an hCG-like material purified from a bacteria, Xanthomonas maltophilia (PCG), were able to increase the rate of transition when compared with the controls. The effect of the two hormones and the bacterial peptide were specific, as human follicle stimulating hormone (hFSH), thyroid stimulating hormone (hTSH), growth hormone (hGH), prolactin (hPrl) and rat and bovine LH (rLH, bLH), and bovine albumin and gamma globulin did not affect the transition. The binding of 125I-hCG or 125I-LH to spheroplasts of Candida albicans were competitively displaced by hCG, hLH, and PCG. Scatchard analysis of binding of all three ligands revealed two binding sites with a high-affinity nM Kd. Thus, hCG, hLH, and PCG induce transition of Candida albicans from a blastospore state to a mycelium form, suggesting that these hormones may modify the pathogenicity of Candida albicans.

Ultrasensitive, specific, two-antibody immunoradiometric assay that detects free alpha subunits of glycoprotein hormones in blood of nonpregnant humans

This noncompetitive, sensitive, immunoradiometric assay of the free alpha subunit of human pituitary glycoprotein hormones is based on two monoclonal antibodies and an avidin-biotin separation system. The affinity of the first antibody, mouse anti-alpha subunit covalently conjugated to biotin, is 3.8 x 10(11) L/mol. The second antibody, radiolabeled with 125I, has an affinity of 5.4 x 10(11) L/mol. A polystyrene ball coated with avidin serves as the separation system. Tests of "purified" immunochemical-grade intact human glycoprotein hormones yielded cross-reactions of approximately 2% in the assay. Sephadex G-100 column chromatography showed that this "cross-reaction" was caused by contamination of the various hormone preparations with free alpha subunit. When the intact glycoprotein hormones were further purified with specific anti-alpha monoclonal antibody, their reaction in the alpha subunit assay was undetectable (less than 0.01%). Interassay CV averaged 3.5%, and intra-assay CV averaged 7.5% at low concentrations of subunit. The detection limit of the assay (0.01 micrograms/L) is adequate to detect free alpha subunit in the blood of normal humans. Mean (SD) concentrations of free alpha subunit in normal humans were as follows: eugonadal men = 437 (35) ng/L; postmenopausal women = 1231 (40) ng/L; eugonadal women, follicular phase = 1061 (40) ng/L; eugonadal luteal phase = 780 (45) ng/L.

Isolation of a 30 kDa immunoglobulin binding protein from Pseudomonas maltophilia

We have demonstrated that Pseudomonas maltophilia (ATCC No. 13637) possesses an exposed, immunologically accessible protein which binds to the Fc region of several species of immunoglobulins. Whole bacteria suspensions were incubated for 18 h with purified 125I-labelled antibodies with and without added non-labelled immunoglobulins. The suspensions were centrifuged for 30 min and the pellet containing bacteria was assessed for radioactivity. Using this crude assay, the whole organism bound 125I-labelled rabbit and mouse immunoglobulins and the purified Fc portion of human IgG. All of these labelled preparations were competitively displaced by unlabelled rabbit and mouse immunoglobulins, and Fc of human IgG, as well as human immunoglobulin subclasses. The organism was sonicated to solubilize this immunoglobulin binding protein. Using this sonicated preparation, it was shown that unlabelled Fc of IgG, unlabelled mouse and rabbit immunoglobulins, all competitively displaced 125I-labelled human Fc of IgG in a dose-response manner. A partially purified protein was prepared by Sephacryl S-300 followed by Sephadex G-100 column chromatography. This preparation was incubated with 125I-Fc gamma and with the following purified unlabelled preparations: F(ab')2 of IgG, Fc of IgG, murine monoclonal IgA, IgG1, IgG2, IgG3, and IgG4. All except F(ab')2 of IgG produced dose response competitive displacement. The molecular weight, as estimated by SDS-PAGE and Western blot, was 30,000 daltons. In Western blots, Fc gamma, murine monoclonal IgA, and human immunoglobulin subclasses, all showed affinity for the immobilized protein. Human F(ab')2 fragments did not show affinity for the protein. Radioiodinated pseudomonal Ig-binding protein showed affinity for human IgG coupled to Sepharose, and was displaced by unlabelled pseudomonal Ig-binding protein. Scatchard analysis of binding showed two binding affinities: two distinct types of Ig-binding proteins were obtained, a high affinity with Kd = 1.54 x 10(-10) and a lower affinity with Kd = 2.36 x 10(-8). This immunoglobulin binding protein may be useful in immunoglobulin purification or identification.

Isolation of a 48.5-kDa membrane protein from Pseudomonas maltophilia which exhibits immunologic cross-reaction to the beta-subunit of human chorionic gonadotropin

In separate studies we have shown that Pseudomonas maltophilia (American Type Culture Collection 13637) possesses an immunoglobulin Fc-binding protein. We have found that this protein prevents the application of immunoassays using monoclonal antibodies to study possible production of a CG-like material by this bacteria. Employing an immunoglobulin saturation technique to block this protein as well as a zwitterion detergent membrane solubilization technique, we now report the isolation of a membrane protein from Pseudomonas maltophilia which shows immunological relationships to the beta-subunit and carboxyl tail of human pregnancy CG. This pseudomonas immunoreactive material produced dose-response curves in the following CG immunoassays: 1) a polyclonal rabbit anti-CG equilibrium assay, 2) carboxyl tail CG equilibrium assay, and 3) two CG equilibrium assays using monoclonal antibodies. The pseudomonas CG-like protein did not react in equilibrium assays for human TSH, human LH, or free alpha-subunit of CG. The pseudomonas CG-like protein was purified by affinity chromatography. The purified protein showed only 0.25% cross-reaction with pregnancy CG in the monoclonal antibody equilibrium assays. Furthermore, the purified protein showed no binding to rat testicular CG/LH receptors, but showed avid binding to the pseudomonas CG-binding protein previously described by Richert and Ryan. The pseudomonas protein showed no binding to Concanavalin-A, which avidly binds pregnancy CG. When assessed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting, this protein had a mol wt of 48,500 daltons, which is larger than the mol wt of the unglycosylated beta-subunit of pregnancy CG. We conclude that pseudomonas contain a protein that has partial homology to the beta-subunit of pregnancy CG. This material does not bind to mammalian CG receptors, but does bind to a pseudomonas CG-binding site. The latter suggests it has a function, as yet unknown, in pseudomonas.

Ectopic ACTH secretion. A misnomer

Ectopic ACTH production is a common cause of Cushing's syndrome. In most patients, the neoplasm is obvious and is readily identified as the source of ACTH. However, in some patients, the neoplasm is not obvious and differentiating the tumor from a pituitary source is difficult. Current data demonstrate that virtually all normal tissues produce small amounts of a biologically inactive precursor ACTH molecule, probably proopiomelanocortin (POMC). All cancers produce this same substance in increased quantities. Selected cancers, correlated with histologic type, convert POMC to biologically active ACTH to produce the so-called ectopic ACTH syndrome. In this context, ectopic ACTH production is not ectopic.

Purified preparations of human luteinizing hormone are contaminated with small amounts of a chorionic gonadotropin-like material

We have identified a CG-like protein contaminating a purified human LH preparation of immunochemical grade. This CG-like material is estimated to comprise 0.17%, by weight, of the LH and reacts in specific, sequential-type, two-monoclonal antibody, immunoradiometric assays for CG as well as in the carboxyl-tail CG RIA. The CG-like material is not separable from LH by size exclusion or ion exchange chromatography. The LH can be freed of this small contamination of CG-like material by immunopurification employing specific monoclonal antibodies. Sephadex G-100 chromatography shows this material to have a mol wt of 40.0K. Western blot analysis of the LH run under nonreducing conditions, using an anti-CG carboxyl-tail primary antibody, reveals two bands of this CG-like material, one at 60.8K and one at 50.7K. When electrophoresed under reducing conditions, the material reacts with the anti-CG carboxyl-tail antibody at several mol wt, ranging from 10.5-64K.

A chorionic gonadotropin-secreting human pituitary cell

Recent data from our laboratory show that hCG is secreted in a pulsatile manner in parallel with human LH (hLH) in nonpregnant normal humans. Furthermore, GnRH stimulates hCG and hLH release. Using a monoclonal antibody specific for the beta-chain of hCG and not reacting with hLH, we have identified a heretofore unknown cell type in human pituitaries which stains only for hCG. The light microscopic, immunocytochemical, and ultrastructural features are described. These data coupled to those from multiple earlier studies indicate that hCG is secreted by these cells in normal nonpregnant humans.

Uterine binding sites for LH/hCG can be modulated by hormonal status in rabbits and rats

High-affinity LH/hCG binding sites have been identified in both porcine and rabbit uteri. We have now identified these binding sites in rat uteri. We have assessed the binding site specificity and modulation and have searched for binding sites for a related glycoprotein. Radioreceptor assays were performed with membrane homogenates of uterine tissue, and were analysed for binding site specificity, affinity, and capacity. The rabbit and rat LH/hCG binding sites did not bind human TSH or human FSH. Rabbit uterine tissue contained no binding sites for FSH, as determined with 125I-labelled FSH and unlabelled FSH. Pretreatment of rabbits with hCG decreased their uterine binding site capacity from 1.30 +/- 0.29 to 0.46 +/- 0.01 fmol/mg protein. Pretreatment of castrated rabbits with estrogen or estrogen combined with progesterone did not alter the binding site affinity or capacity. In rats, the uterine binding site number was shown to vary inversely with the serum LH concentration and directly with the ovarian LH/hCG binding site number during the estrus cycle. Hypophysectomy resulted in a significant increase in uterine binding site capacity in rats. Estrogen treatment prevented this hypophysectomy-induced increase. The function of these LH/hCG binding sites remains uncertain; however, the lack of binding sites for a related glycoprotein and the modulation of these binding sites by hormonal factors strengthen the concept that uterine tissue might respond in a specific manner to direct LH/hCG stimulation.

Chorionic gonadotropin secretion in normal, nonpregnant humans

A chorionic gonadotropinlike material is present in blood and urine of normal, nonpregnant humans, is secreted in pulsatile fashion in parallel with luteinizing hormone, is stimulated by gonadotropin-releasing hormone, and is suppressed by GnRH agonists and estrogen. The source is probably the pituitary gland.

Secretion of chorionic gonadotropin by cultured human pituitary cells

To investigate the possibility that the human pituitary gland secretes CG, we used a highly specific, two-site, double monoclonal immunoradiometric assay to measure CG in the medium in which the dispersed cells of pituitary glands from human fetuses of 20-24 weeks gestation were cultured. The cross-reactivity of immunopurified human LH in the CG assay was less than 0.03%. LH was also measured by a double monoclonal immunoradiometric assay. Secretion of CG by the cultured fetal pituitary cells was readily detectable, although in gradually decreasing amounts, for the 11 days of culture. LH secretion paralleled CG secretion and was much greater in magnitude. Pituitary cells from female fetuses generally secreted more CG as well as more LH than those from male fetuses. Dilutions of the medium showed that the secreted CG exhibited parallelism with the CG standard. Chromatofocusing of the medium across a pH 6-9 gradient yielded several peaks of LH immunoreactivity between pH 6.5 and 8.5, but no peaks of CG. Chromatofocusing of the medium across a pH 3-7 gradient yielded peaks of CG, but not LH, between pH 4.0-5.5. These data indicate that CG immunoreactivity, distinct and separable from LH immunoreactivity, is secreted by the dispersed cells of fetal human pituitary glands.

Prolactin inhibition of pregnant mare's serum stimulated follicle development in the rat ovary

Prolactin (PRL) effects on the female reproductive system have been presumed to occur primarily at the hypothalamic-pituitary level. The following studies were designed to evaluate whether PRL can directly alter gonadotropin actions at the ovarian level. In the first experiment, 10 groups of 7 cycling adult female rats were given a daily dose of pregnant mare's serum (PMS: 25 IU) and either saline (SAL) or PRL (0.25, 0.8, 2.5, 8, or 25 micrograms) twice daily for 4 days. In the second experiment, PMS (6 doses: 0-75 IU/d; 16 animals/dose) was administered to all animals while half the animals at each PMS dose received PRL (25 micrograms twice daily) and half received an equal volume of diluent. Finally, hypophysectomized (hypox) adult rats (n = 5-6/group) received 25 IU PMS/d and PRL (0-75 micrograms) twice daily. An additional group received 0 PRL and 0 PMS. Ovarian weight and histology were evaluated at the completion of each study. In the first experiment, PRL inhibited PMS-stimulated ovarian weight gain in a dose-dependent manner (p less than 0.01). Numbers of preantral (p less than 0.005) and antral (p less than 0.05) follicles were decreased in animals receiving an inhibitory dose of PRL (25 micrograms BID) compared to controls. In the second experiment PRL (25 micrograms BID) again inhibited PMS-stimulated ovarian weight (p less than 0.01) at all doses of PMS. Finally, in hypox animals, PRL inhibited PMS-stimulated ovarian weight gain (25 and 75 micrograms PRL: p = 0.001), and mean number (p less than 0.001) and diameter (p less than 0.001) of antral ovarian follicles (8-75 micrograms PRL) compared to controls. In summary, administration of PRL inhibited PMS-stimulated ovarian weight gain, and antral follicle diameter (in hypox animals only) and number in adult female rats suggesting that in states of hyperprolactinemia, PRL alters gonadotropin-mediated activities (i.e., folliculogenesis) directly at the ovarian level in addition to its hypothalamic and pituitary actions.

Pulsatile secretion of chorionic gonadotropin during the normal menstrual cycle

Several groups of investigators have previously reported that small amounts of hCG are present in blood and urine of nonpregnant eugonadal women and men. We have developed highly sensitive and specific, two-monoclonal antibody, sandwich-type assays which can quantify both hCG and LH in sera from postmenopausal women, women at all phases of the menstrual cycle, and men. Using these assays we have also reported that hCG is secreted in a pulsatile fashion in postmenopausal women, is stimulated by GnRH in both men and postmenopausal women, and is suppressed by a GnRH agonist in castrate men. Employing these same sandwich assays, we report herein that hCG is secreted in a pulsatile manner during the follicular and luteal phases of the normal menstrual cycle. During the follicular phase 0.68 +/- 09 (+/- SEM) pulses of hCG occurred each hour, while 0.62 +/- 0.08 pulses of LH occurred. Pulse durations during the follicular phase for hCG and LH, respectively, were 38.3 +/- 4.4 and 62.5 +/- 11.1 min (P less than or equal to 0.05). During the luteal phase there were 0.42 +/- 0.16 pulses/h of hCG and 0.38 +/- 0.08 pulses of LH (P greater than 0.05). Pulse durations were 22.3 +/- 7.5 and 126.4 +/- 19.0 min for hCG and LH, respectively (P less than 0.01). The t1/2 of hCG disappearance was 37.2 +/- 3.8 min during the follicular phase and 22.9 +/- 4.6 min during the luteal phase. The t1/2 values of LH were 82.9 +/- 5.7 and 67.5 +/- 5.12 min during follicular and luteal phases, respectively. The t1/2 of LH was greater than the t1/2 of hCG (P less than 0.01). We conclude that small amounts of hCG are secreted in a pulsatile manner during follicular and luteal phases of the human menstrual cycle.

Inability to demonstrate an ultrashort loop feedback mechanism for luteinizing hormone in humans

hCG has biological properties similar to those of LH, but can be measured separately from LH by current radioimmunometric assays. To investigate the possible existence of an autoregulatory mechanism for LH in humans, we compared the basal LH concentrations and the LH response to a GnRH stimulus with and without prior administration of hCG. On two separate occasions, at least 1 week apart, six normal (eugonadal) males and six normal postmenopausal females were given, in random order, either 10,000 IU hCG or saline followed by iv injection of a 200-micrograms bolus of GnRH. Blood samples were then taken 30, 60, 90, 120, 180, 240, and 300 min after GnRH. Serum concentrations of LH and hCG were measured at each time by two monoclonal antibody sandwich assays developed in our laboratory. After exogenous hCG, serum hCG concentrations rose rapidly to 200-500 IU/L (15,000-35,000 pg/mL) in both the men and women, remaining at this high level throughout the study. In the men, sex steroid concentrations did not change in response to the hCG during the 9 study hours. Compared to saline-treated controls, hCG had no significant effect in either men or postmenopausal women on the basal LH concentration or the response to a GnRH bolus, as determined by peak response and area under the LH/time curve between 0-300 min after GnRH. We conclude that an ultrashort loop feedback mechanism for LH on its own secretion does not exist in humans, as assessed by the present protocol.

Secretion of multiple forms of human luteinizing hormone by cultured fetal human pituitary cells

Previous studies of the heterogeneity of human LH have employed LH stored within the pituitary gland. In this study we characterized LH secreted by dispersed fetal human pituitary cells. Chromatofocusing across a pH 9-6 gradient of the medium in which fetal pituitary cells had been grown yielded at least eight distinct peaks of LH immunoreactivity. The more basic LH peaks bound more strongly to Concanavalin-A-Sepharose than did the more acidic ones, suggesting that the more basic LH molecules contain more hybrid oligosaccharides, in which one antenna terminates in a mannose, and that the more acidic human LH molecules contain more complex oligosaccharides, in which both antennae terminate in negatively charged groups, sialic acid and/or N-acetylgalactosamine-sulfate. The biological/immunological activity (B/I) ratios of the secreted LH varied directly and dramatically with the pI, from 8.1 at pI 8.4 to 1.1 at pI 6.3. Secreted LH, therefore, exhibits similar heterogeneity of glycosylated forms as does stored LH, raising the possibility that the hormones that control overall LH secretion could affect the secretion of some isohormones more than others and thereby influence LH biological activity to a degree not predicted by measuring total LH immunoreactivity.

Immunoradiometric assay of corticotropin with use of avidin-biotin separation

We have developed a "sandwich"-type immunoradiometric assay for corticotropin (ACTH), with a detection limit of 2 ng/L. Two antibodies are used: a mouse monoclonal antibody directed against ACTH[1-17] and labeled with 125I; and a purified polyclonal goat antibody directed against ACTH[34-39] and conjugated to biotin. We could separate 125I-labeled antibody bound to ACTH from 125I-labeled antibody not bound to ACTH by using an avidin-biotin bridge, with avidin bound to a polystyrene ball. This assay reacts with ACTH[1-39] but shows no reaction with ACTH fragments [1-24], [1-17], or [34-39], or with melanotropin, endorphins, or lipotropin. This assay is sensitive enough to detect ACTH in plasma of all normal adults. Concentrations measured in 94 adults between 0800 and 1000 hours were normally distributed on a log scale, with a mean of 19.5 ng/L and a 95% range of 7.1 to 53.8 ng/L. Dexamethasone given at 2300 hours to 14 adults suppressed ACTH to less than 4 ng/L in 13 of the subjects and to 8 ng/L in the 14th. Metyrapone given to 13 adults at 2300 hours increased ACTH to 245.3 ng/L (95% range, 90.1 to 667.7 ng/L). This assay accurately classified patients with disorders of the adrenal system.

Immunoradiometric assay of corticotropin with use of avidin-biotin separation

We have developed a "sandwich"-type immunoradiometric assay for corticotropin (ACTH), with a detection limit of 2 ng/L. Two antibodies are used: a mouse monoclonal antibody directed against ACTH[1-17] and labeled with 125I; and a purified polyclonal goat antibody directed against ACTH[34-39] and conjugated to biotin. We could separate 125I-labeled antibody bound to ACTH from 125I-labeled antibody not bound to ACTH by using an avidin-biotin bridge, with avidin bound to a polystyrene ball. This assay reacts with ACTH[1-39] but shows no reaction with ACTH fragments [1-24], [1-17], or [34-39], or with melanotropin, endorphins, or lipotropin. This assay is sensitive enough to detect ACTH in plasma of all normal adults. Concentrations measured in 94 adults between 0800 and 1000 hours were normally distributed on a log scale, with a mean of 19.5 ng/L and a 95% range of 7.1 to 53.8 ng/L. Dexamethasone given at 2300 hours to 14 adults suppressed ACTH to less than 4 ng/L in 13 of the subjects and to 8 ng/L in the 14th. Metyrapone given to 13 adults at 2300 hours increased ACTH to 245.3 ng/L (95% range, 90.1 to 667.7 ng/L). This assay accurately classified patients with disorders of the adrenal system.

Effects of prolactin on luteinizing hormone-stimulated testosterone secretion in isolated perfused rat testis

The direct peripheral effect of prolactin on LH-stimulated testosterone secretion was re-evaluated using the intact, isolated, perfused rat testis. In paired experiments, one testis was infused with the hormones being studied; the other testis of the same rat was used as the control. A dose-response curve of LH-stimulated testosterone secretion was established first. A dose of 300 ng of LH, which was on the ascending portion of the dose-response curve, was selected so that both stimulatory and inhibitory effects of prolactin could be observed. Prolactin doses ranging from 0 ng to 3000 ng were then tested to determine alterations in LH-stimulated testosterone secretion. Prolactin inhibited LH-stimulated testosterone secretion at low doses (less than 300 ng), but augmented LH action at high doses (greater than 1000 ng). These results showed that prolactin and LH interact with each other in a biphasic dose-dependent manner.

Identification of LH/hCG receptors in rabbit uterus

Luteinizing hormone (LH) is believed to act via specific receptors to control gonadal steroidogenesis and reproductive processes. Recently A. J. Ziecik, P. D. Stanchev, and J. E. Tilton (Endocrinology 119:1159, 1986) reported surprisingly that LH/hCG receptors were present in porcine uterus, a tissue not known to be a target for LH action. We report herein the identification of high-affinity LH receptors in the rabbit uterus. Uteri from adult New Zealand white rabbits were homogenized in Tris-HCl, 0.25 M sucrose. After filtration and sequential centrifugation, a partially purified pellet containing receptors was obtained. This preparation was incubated with a trace (1300 cpm) (50 pg) 125I-labeled chorionic gonadotropin and with various unlabeled protein hormones. Receptor bound was separated from free hormone by centrifugation at 1000 g. Affinity was estimated by Woolf plot analysis. Specific binding sites for LH/hCG were identified. The following Kd's were calculated: human LH, 1.6 X 10(-11); hCG, 0.5 X 10(-11); human TSH, 1.3 X 10(-9); and human FSH, 7.85 X 10(-9). The reaction of human FSH and TSH with the receptor is best explained by LH contamination of these hormones. A similar preparation of rat liver showed that no binding sites were present. Rabbit ovarian LH receptors had a Kd slightly higher at 4.1 X 10(-11) than that of the uterine LH receptors. Rabbit ovarian receptors were present at 2.27 X 10(-13) M/mg protein compared to uterine receptors at 4.65 X 10(-15) M/mg protein. We conclude specific- and high-affinity binding sites (receptors) for LH are present in the rabbit uterus. The function of these receptors remains unknown.

Pulsatile secretion of human chorionic gonadotropin in normal adults

We used very sensitive and specific monoclonal-antibody sandwich assays for human chorionic gonadotropin (hCG) and human luteinizing hormone (hLH) to measure both hormones in serum samples from normal men and women. When single serum samples from 92 men were studied, 73 percent had detectable hCG. In normal men, the amount of detectable hCG averaged 8.9 pg per milliliter, with a range of less than 3.0 to 160 pg per milliliter (biologic potency = 13,450 IU per milligram). In postmenopausal women the hCG level averaged 111 pg per milliliter and ranged from 32 to 510. In women of reproductive age the hCG level varied with the menstrual cycle. Gonadotropin-releasing hormone administered to 10 normal men increased both hCG and hLH. When daily serum samples were studied throughout a normal menstrual cycle, hCG concentrations paralleled those of hLH; follicular-phase concentrations were higher than those of the luteal phase, and there was a midcycle ovulatory peak of hCG coincident with the hLH peak. When hCG was measured every 10 minutes for six hours in eight postmenopausal women, distinct pulses were detected in parallel with those of hLH: hLH pulsed at a mean (+/- SEM) frequency of 0.56 +/- 0.08 pulses per hour; hCG pulsed at 0.54 +/- 0.07 pulses per hour. The mean pulse durations were 89 +/- 22 and 56 +/- 20 minutes for hLH and hCG, respectively. We conclude that hCG is produced in a pulsatile fashion, probably by the pituitary, in all normal adults.

Ultrasensitive immunoradiometric assay for chorionic gonadotropin which does not cross-react with luteinizing hormone nor free beta chain of hCG and which detects hCG in blood of non-pregnant humans

We have developed a sensitive, non-competitive, two-monoclonal antibody, sandwich-type or immunoradiometric assay for human chorionic gonadotropin (hCG) which shows no cross-reaction with the free beta chain of hCG nor with human luteinizing hormone (LH). In the assay procedure, two, highly selected monoclonal antibodies reacted in solution with hCG to be quantified. One antibody was covalently conjugated to biotin. This antibody was specific for the beta subunit of hCG, and showed no reaction with LH nor the alpha subunit. The second antibody was labelled with 125I and was specific for intact hCG and LH, showing no cross-reaction with beta hCG nor the alpha subunit. The separation system was a polystyrene ball conjugated with biotin. This ball bound via an avidin bridge the monoclonal 'sandwich' containing hCG. Counts per minute bound to the ball were directly proportional to the amount of hCG present. The assay was specific for whole hCG and showed no reaction with beta hCG, beta LH, intact LH nor the free alpha subunit. Sensitivity was adequate to detect 'hCG-like' material in all post menopausal women and, when single samples were obtained, in over 2/3 of normal men. When multiple samples were obtained, 'hCG-like' material was detectable in all eugonadal adults studied.

Two-monoclonal-antibody "sandwich"-type assay of human lutropin, with no cross reaction with choriogonadotropin

We have developed a sensitive, specific, noncompetitive sandwich-type assay for human lutropin (hLH). Two monoclonal antibodies are used, and there is no cross reaction with human choriogonadotropin (hCG) or human follitropin (hFSH), and little or none with human thyrotropin (hTSH). There also is no reaction with the free beta chains of hLH and hCG. The detection limit is less than 0.5 int. units of hLH per liter of serum, and the dose-response curve is linear between 0 and 10 int. units/L. The intra-assay CV averaged 5.4% at low doses of hLH; the interassay CV averaged 12.5%.

Two-monoclonal-antibody "sandwich"-type assay of human lutropin, with no cross reaction with choriogonadotropin

We have developed a sensitive, specific, noncompetitive sandwich-type assay for human lutropin (hLH). Two monoclonal antibodies are used, and there is no cross reaction with human choriogonadotropin (hCG) or human follitropin (hFSH), and little or none with human thyrotropin (hTSH). There also is no reaction with the free beta chains of hLH and hCG. The detection limit is less than 0.5 int. units of hLH per liter of serum, and the dose-response curve is linear between 0 and 10 int. units/L. The intra-assay CV averaged 5.4% at low doses of hLH; the interassay CV averaged 12.5%.