Biological Activity Of Luteinizing Hormone Research Articles

Biological function of the LH receptor is associated with slow receptor rotational diffusion

The biological activity of luteinizing hormone (LH) receptors can be affected by modifications to the receptor’s amino acid sequence or by binding of hormone antagonists such as deglycosylated hCG. Here we have compared rotational diffusion of LH receptors capable of activating adenylate cyclase with that of non-functional hormone-occupied receptors at 4°C and 37°C using time-resolved phosphorescence anisotropy techniques. Binding of hCG to the rat wild-type receptor expressed on 293 cells (LHR-wt cells) or to the LH receptor on MA-10 cells produces functional receptors which exhibit rotational correlation times longer than 1000 μs. However, modification of the LH receptor by substitution of Lys583→Arg (LHR-K583R) results in a receptor that is non-functional and which has a significantly shorter rotational correlation time of 130±12 μs following binding of hCG. When these receptors are treated with deglycosylated hCG, an inactive form of hCG, the rotational correlation times for the LH receptors on LHR-wt and MA-10 cells are also shorter, namely 64±8 and 76±14 μs, respectively. Finally, a biologically active truncated form of the rat LH receptor expressed in 293 cells (LHR-t631) has slow rotational diffusion, greater than 1000 μs, when occupied by hCG and a significantly shorter rotational correlation time of 103±12 μs when occupied by deglycosylated hCG. The effects of rat LH binding to LH receptors on these various cell lines were similar to those of hCG although the magnitude of the changes in receptor rotational diffusion were less pronounced. We suggest that functional LH receptors are present in membrane complexes that exhibit slow rotational diffusion or are rotationally immobile. Shorter rotational correlation times for non-functional hormone–receptor complexes may reflect the absence of essential interactions between these complexes and other membrane proteins.

Hormonal Ergogenic Aids

Most hormonal agents used for nonmedical purposes in athletes have legitimate medical uses. This review introduces each compound by its pharmacology, clinical pharmacology, and legitimate medical use and reviews information on its abuse. Human growth hormone is presently available in virtually unlimited quantities due to its production by recombinant DNA technology. Its use in athletes is considered for its muscle-building, fat-depleting properties. Erythropoietin is a kidney hormone that increases red cell mass. It is used for renal dialysis patients to avoid blood transfusions. Its use in athletes is to raise red blood cell mass in an attempt to augment maximal oxygen capacity and the ability to do endurance work. Human chorionic gonadotropin has the biological activity of luteinizing hormone to increase testosterone synthesis and to maintain (partially) testicular volume when exogenous androgens are taken. Clenbuterol is a beta2adrenergic agonist with muscle-building properties that are seemingly specific to striated muscle; clenbuterol may cause reduction in body fat.

Time-resolved fluoroimmunoassay compared with radioimmunoassay of luteinizing hormone

To determine if fluoroimmunoassay (FIA) of serum luteinizing hormone (LH) is more useful clinically than a conventional radioimmunoassay (RIA) because it has been suggested that FIA closely reflects biological activity. Comparison of serum LH measurements by RIA and FIA during various perturbations in normal ovulatory women and in women with polycystic ovarian syndrome (PCOS). Normal ovulatory subjects were healthy volunteers and women with PCOS were untreated and newly diagnosed outpatients in our Reproductive Endocrinology/Infertility Clinic, Women's Hospital, at the Los Angeles County+University of Southern California Medical Center. Fifty-three normal ovulatory women, ages 20 to 35, and 27 women with PCOS, ages 21 to 35. All were in good health and received no other medications during the study period. Fluoroimmunoassay of serum LH reflected status of known altered bioactivity better than with a conventional RIA. This was most evident during conditions of gonadotropin suppression and in patients with PCOS. An excellent correlation was found between values of FIA and RIA. The measurement of LH by FIA is clinically useful, specifically when a change in biological activity of LH is sought.

Biological activity of luteinizing hormone in uraemic children: spontaneous nocturnal secretion and changes after administration of exogenous pulsatile luteinizing hormone-releasing hormone ? preliminary observations

Normal pubertal progression is associated with quantitative and qualitative changes in gonadotrophin release. Uraemic children show a delayed or disturbed puberty. We have therefore examined nocturnal gonadotrophin and sex steroid secretion in seven males and three females [age 11-15 years, pubertal stage (PS) 1-3] with chronic renal failure on conservative treatment. In addition to immunoreactive luteinizing hormone (i-LH) we have measured the biological activity of LH (b-LH). Nine children aged 12-17 years with PS 1-3 and normal renal function served as a control group. In two uraemic children, i-LH, b-LH, follicle stimulating hormone and sex steroids were evaluated before and 7 days after pulsatile LH-releasing hormone (LHRH) administration (150 ng/kg body weight subcutaneously every 120 min). Mean i-LH levels were higher in uraemic children than in controls. An increase in i-LH during sleep was found in all controls and in eight of ten uraemic subjects. Mean b-LH levels were lower during sleep and the b/i LH ratio was reduced in uraemic children with PS 2-3 whether asleep or awake compared with controls. Pulsatile administration of LHRH provoked a rise of i-LH and b-LH levels with an increased b/i LH ratio, suggesting an intact pituitary responsiveness. These preliminary data indicate that the gonadotrophin control of LH is abnormal in uraemic children, and that biopotency of LH secretion might be improved after short-term pulsatile LHRH administration.

Lemur Species Show Differences in Immunological and Biological Activity of Luteinizing Hormone

Lemur Species Show Differences in Immunological and Biological Activity of Luteinizing Hormone

The Pulsatile Secretion of Gonadotropins and Growth Hormone, and the Biological Activity of Luteinizing Hormone in Men Acutely Intoxicated with Ethanol

The effects of acute alcohol ingestion were studied on pulsatile secretion of immunoreactive luteinizing hormone (LH), follicle-stimulating hormone (FSH), and growth hormone (GH), and on serum bioactive LH, testosterone, cortisol, and prolactin. A dose of 1.5 g ethanol per kg of body weight was administered by mouth to eight healthy male volunteers (aged 20 to 26 years) during 3 hr from 1800 to 2100 hr. Blood samples were collected every 20 min for 20 hr until 1400 hr of the following day. Each subject served as his own control in an identical experiment without ethanol, carried out at least 1 month later. Ethanol ingestion decreased serum testosterone concentration on average by 23% (p less than 0.05) between 10 and 16 hr after starting the drinking. The mean levels of LH and FSH and the mean number and amplitude of LH and FSH pulses remained unchanged. Ethanol ingestion did not affect the biological activity of LH. In each subject alcohol administration reduced the nightly peak of GH secretion, and in addition, changed the timing of this peak in most subjects. Only marginal changes were found in the prolactin levels but ethanol ingestion increased the cortisol levels on average by 36% (p less than 0.05) between 11 and 14 hr after the start of drinking. We conclude that the decrement in serum testosterone evoked by ethanol is not attributable to impaired pulsatile secretion of gonadotropins nor to reduced biological activity of LH. In contrast, ethanol profoundly suppressed the pulsatile secretion of growth hormone.

Biological activity of LH during the peripartum period and the estrous cycle of the ewe

Biological activity of luteinizing hormone (LH) is related to the degree of glycosylation of the glycoprotein hormone. The objectives of this study were to determine changes in biologically (BLH) and immunologically (ILH) active LH concentrations in plasma ( in vitro bioassay and radioimmunoassay, respectively) and in the ratio of BLH to ILH (B:I) during the peripartum period and during the estrous cycle of the ewe. Blood samples were collected daily 4 days before through 4 days after parturition and during one estrous cycle. Also, samples were collected at 15-min intervals for 6 hr on Days 3 and 12 of the estrous cycle to quantify the influence of an elevated plasma concentration of progesterone (P) on the episodic secretion profiles of BLH. Progesterone concentration was determined on the 4th days pre- and post-partum, on each day of the estrous cycle and at hourly intervals on Days 3 and 12 of the cycle to investigate the hypothesis of an inverse relationship between P and BLH. The BLH and ILH concentrations were low during the peripartum period, and the B:I ratio did not increase by the 4th day postpartum. Mean ILH concentration was greater (P<.05) in the postpartum than during the prepartum period. During the estrous cycle, mean daily B:I ratio was consistently above unity except for the day of estrus. The pre-ovulatory LH surge (BLH and ILH) was associated with a decrease (P<.05) in the mean B:I ratio to 0.065. Mean concentrations of BLH and ILH in plasma samples collected every 15 min on Day 12 were similar to Day 3 of the cycle. On Day 12 the frequency of BLH and ILH pulses decreased (P<.05), but the peak height was not different from Day 3. These data indicate that both biological and immunological activity of LH are suppressed during late gestation and the escape from the suppressive effects of gestation is more rapid for immunological than for biological activity of LH. In addition, the change in B:I ratio during estrus demonstrates differences in biological potency of LH associated with the preovulatory LH surge. We suggest that factors of placental and ovarian origin may influence biological activity of LH in the ewe.

Biological activity of luteinizing hormone in the peripartum cow: least activity at parturition with an increase throughout the postpartum interval.

The biological (B) and immunological (I) activities of luteinizing hormone (LH) were determined during four peripartum periods in the cow. The sampling periods were PRE-5 (approximately 5 days prior to parturition), POST-3 (Day 2 or 3 postpartum), POST-12 (Day 11 or 12 postpartum) and LUTEAL (Day 11 or 12 following the first observed postpartum estrus). Blood samples were collected at 10-min intervals for either 8 h (PRE-5, POST-3, and POST-12) or 6 h (LUTEAL). Four hours prior to the end of each sampling period, 100 micrograms of luteinizing hormone-releasing hormone (LHRH) was injected i.v. Plasma concentrations of LH were analyzed by a validated bioassay (rat interstitial cell testosterone) and a radioimmunoassay. Area under the LHRH-induced LH release curve was calculated by the trapezoidal rule, and endogenous LH was determined by averaging the pre-LHRH treatment values. Paired t-analyses were used to compare LH release between periods. The periods of lowest (p less than 0.05) bioactive LH (BLH) were PRE-5 and POST-3. During POST-12, BLH was maximal. Endogenous immunoactive LH (ILH) was maximal during the POST-12 period, with PRE-5, POST-3, and LUTEAL being the least (p less than 0.05). The B:I ratio was lowest (p less than 0.05) around the time of parturition (PRE-5 and POST-3), then increased (p less than 0.05) by Day 12 postpartum. The ratio then increased (p less than 0.05) again by the LUTEAL period. These data suggest that the biological quality of LH changes throughout the puerperium. We infer from these data that the low biological activity of LH (subquality LH) may contribute to the postpartum infertility in the cow.

Biological activity of Luteinizing Hormone (LH) during the estrous cycle of mares

Equine luteinizing hormone (LH) contains a high proportion of carbohydrate (27%) and large compliment of sialic acid residues (6%), and anterior pituitary stores exhibit high physiochemical polymorphism. We initiated studies to determine whether polymorphism in the pituitary was reflected in secretory forms of LH as divergence between biopotency and immunoreactivity. Serum samples were collected daily from mares throughout the estrous cycle. In addition, the dynamics of LH secretion was monitored during intensive collection periods during estrus and the mid-luteal phase. Immunoreactive LH (iLH) was evaluated using conventional radioimmunoassay procedures. The biological activity of LH (bLH) was determined using a mouse interstitial cell-testosterone bioassay. The relative biopotency of equine LH (bLH/iLH,B/I) is significantly (P<0.05) greater during the preovulatory (1.69 ± 0.11) and luteal (1.45 ± 0.07) phases of the cycle than during the period of luteal regression (1.11 ± 0.07). These data indicate that the secretory forms of equine LH vary through the estrous cycle and suggest that gonadal steroids may influence the processing of the hormone at the pituitary or at an extra-hypophyseal locus.

Differences in immunological and biological activity of serum luteinizing hormone during the bovine estrous cycle

Although immunological luteinizing hormone (LH) profiles have been extensively characterized in several species, an awareness has developed that these immunological LH measurements may not adequately describe the biological activity or stimulation of the target tissue. The objective of this study was to compare serum LH at different stages of the bovine estrous cycle as measured by both bioassay and radioimmunoassay. Blood samples were collected from 5 cows at 10 min intervals for 10 hr on days 3, 10 and 19 of the estrous cycle; for 24 hr at estrus on day 0 (natural preovulatory LH surge, NS); and for 8 hr following administration of luteinizing hormone-releasing hormone (induced LH surge) on day 10 of that cycle. Immunological activity of LH was determined by a previously validated radioimmunoassay. A sensitive and specific in vitro mouse Leydig cell bioassay in which testosterone production was an index of added LH was used to assess biological activity of LH. The same preparation (NIAMDD-bLH4) served as the standard for each assay system. Patterns of biological active LH closely followed those of immunological LH, although biological LH values tended to be lower. Although the pulse frequency (pulses/hr) of immunological LH was lower (P<.05) on day 10 ( .48 ± .07; x ± SE ) than day 3 or 19 (.88 ± .09 and .88 ± .15, respectively), no changes in biological LH pulse frequency were noted (P>.05). The mean biological to immunological (B:I) ratios were greater (P<.05) on days 3 and 10 (0.91 ± .16 and 0.93 ± .12, respectively) than day 19 (0.64 ± .05) and day 0 (0.43 ± .07). The B:I ratios of the natural LH surge and induced LH surge were not different from each other (P>.05). These observations demonstrate that biological LH exhibits a pattern similar to, but not identical to, immunological LH. Furthermore, as evidenced by changing B:I ratios, the pituitary releases LH which is not of the same biological activity at all stages of the estrous cycle. These data suggest that both quality and quantity of LH released may be important in regulating LH action at the target tissue.

Studies on the immunochemical relatedness among tetrapod gonadotropins and their subunits with antisera to sea turtle hormones

Immunological relatedness among gonadotropins from the four classes of tetrapods was studied with three antisera ( a s ) raised in rabbits against follicle-stimulating hormone (FSH), luteinizing hormone (LH), and LHβ subunit from the green sea turtle, Chelonia mydas. Only pituitaries or FSH from turtles showed appreciable cross-reaction in the homologous RIA for Chelonia FSH, and preparations from the heterologous suborder Pleurodira showed weaker and less complete cross-reactivity than from species of Cryptodira. However, the Chelonia FSH a s was capable of neutralizing the biological activity of crocodilian FSH and showed specific binding to 125I-labeled FSH from birds and mammals (but not amphibians). Considerable immunorelatedness was evident among the LH preparations of different species and this appeared to result primarily from common antigenic determinants on the α subunits of LH. First, all chelonian, crocodilian, and avian LH preparations showed high activity in RIA based on anti- Chelonia LH serum and 125I-labeled Chelonia LHα as tracer; in fact, several of these heterologous species of LH were more potent than the Chelonia LH. LH from eutherian mammals (human, ovine, bovine) showed essentially no cross-reactivity, but preparations of ovine LHα and kangaroo LH showed measurable activity in LHα RIA. Second, the antiserum for LH, which contained antibodies to the LHα subunit, neutralized the biological activity of LH from other species of turtles, crocodilians, and a mammal (sheep). Third, 125I-labeled preparations of avian (turkey) and mammalian (ovine and rat) LH showed specific binding to this antiserum. In contrast, parallel tests with an antiserum raised against Chelonia LHβ showed high cross-reactions only with LHs from other species of turtles; i.e., little or no cross-reaction with any nonchelonian species was indicated in RIA, neutralization tests, or binding studies with 125I-labeled hormones. Gonadotropins from amphibians and snakes showed no cross-reaction in any tests with any of the three antisera used. This conspicuous lack of immunological cross-reactivity of snake gonadotropins, especially with antibodies to LHα, provides further evidence for a pronounced structural divergence between the hormones of squamates and the other reptilian orders.

Chemical modification of lysine residues in ovine luteinizing hormone: Effect on biological activity

1. 1.|The amino groups of the lysine residues of ovine luteinizing hormone were modified by reductive alkylation, guanidination and carbamylation. The degree of modification obtained was examined and the biological activity of the derivatives was investigated. 2. 2.|When reductive methylation was performed on native luteinizing hormone, only 50% of the lysine-20 residue in the β-subunit was methylated, showing that this residue is less accessible than the lysine-42 (90% methylated). 3. 3.|Abolition of the positive charges of half the lysine residues of luteinizing hormone (by carbamylation) led to the loss of biological activity, whereas guanidination or methylation produced active derivatives. Isopropylated luteinizing hormone was, on the contrary, almost inactive, probably as a consequence of the elongation of the alkyl chain. Directly methylated luteinizing hormone was more active in the Parlow test than was native luteinizing hormone, whereas reconstituted luteinizing hormone obtained by recombination of an intact subunit with a methylated subunit was less active than native luteinizing hormone or that obtained by recombination of two normal subunits. On the basis of these results the relationship between structure and the biological activity of luteinizing hormone is discussed.

STABILITY STUDIES ON LUTEINIZING HORMONE.

Stability of the biological activity of luteinizing hormone to a range of conditions and agents was studied using the Parlow ovarian ascorbic acid depletion assay. Inactivation was virtually complete after performic acid oxidation, urea denaturation, heating to 100 C in solution, subjection to pH 2 at 25 C or less, reduction by sodium in liquid ammonia, or digestion by the enzymes trypsin or clostripaine. Partial inactivation was observed after limited digestion with chymotrypsin, trypsin, carboxypeptidase A, clostripaine, or incubation with sulfhydrylcontaining compounds. No inactivation was observed following neuraminidase or bacterial a-amylase treatment or short exposure to pH 12. (Endocrinology75: 333, 1964)