Biomedical subjects

S Rosberg

Publications and source records attributed to S Rosberg.

At least 55 records · Page 3Linked to original sources

PubMed1993

Analysis of 24-hour plasma profiles of growth hormone (GH)-binding protein, GH/GH-binding protein-complex, and GH in healthy children.

Human blood contains a high affinity GH binding protein (GHBP) which corresponds to the extracellular domain of he GH-receptor. It has been suggested that GHBP can modify the biological actions of GH, and alter the distribution of GH in the body. To study the hormonal regulation of growth, it is therefore necessary to measure GHBP as well as GH. We recently developed a ligand-mediated immunofunctional assay (LIFA) which allows separate quantitation of total GHBP (free and GH-bound) and the complex formed by GH and GHBP (GH/GHBP-complex) in human blood. We have now used the ligand-mediated immunofunctional assay to measure GHBP levels in plasma profiles from healthy children. GH was measured by immunoradiometric assay. Fifteen 24-h plasma profiles from 12 healthy children (3 girls and 9 boys) of different ages (6-15 yr), heights (-2.5 to +3.0 SD scores) and pubertal stages (1-4) were examined. Blood was withdrawn continuously for 24 h and collected in 20-min fractions. Time series for GH, GHBP, and GH/GHBP-complex were analyzed by cross-correlation and Fourier analysis. GH was secreted in a pulsatile fashion in all subjects. The concentration of the GH/GHBP-complex varied during the sampling period, and the changes correlated significantly with the GH pulses with correlation coefficients reaching maximum at zero time lag. In contrast, the changes in the total GHBP concentration were minor (coefficients of variation approximately 10%), and not correlated to GH pulses. Fourier analysis showed similar spectral power patterns for GH and GH/GHBP-complex, suggesting a diurnal rhythm (12- to 24-h periods) as well as components of higher frequencies (around 4-h periods). Although there were only subtle fluctuations in the total GHBP concentration, Fourier transformation revealed a diurnal rhythm with nadir during the night, while components of higher frequencies were much less abundant. We conclude that variations in total GHBP as measured by LIFA during a 24-h sampling period are small and that the concentration can be estimated from a single random blood sample.

Adolescent↗

PubMed1993

Time-resolved immunofluorometric assay of human growth hormone.

We describe a time-resolved immunofluorometric assay (trIFMA) for human growth hormone (hGH), in which monoclonal antibody (mAb)-coated microtiter strip wells and a europium (Eu) chelate-labeled mAb are used. We compare the new trIFMA, in which two mAbs are used, with an immunoradiometric assay (IRMA) in which polyclonal antibodies are used. Serum samples (n = 185) from 36 children with various diagnoses were analyzed. In addition, 24-h profile samples (72 per child) from 39 children were analyzed. The trIFMA was more sensitive (detection limit, 0.03 mIU/L) than existing IRMAs. Both the intra- and interassay CVs were < or = 10.6% for hGH concentrations between 1 and 100 mIU/L. The trIFMA is technically simple and rapid, requires no centrifugation or separation reagent, and has a counting time of only 1 s per sample. In addition, the Eu label is nontoxic, presents no waste-disposal problems, and has a long shelf-life. Finally, the assay requires only small volumes of serum (25 muL), which is of considerable importance in pediatric use. The mAbs used for the trIFMA selectively bind the 22-kDa form of hGH, with the result that the assay detects about 80% of the amount detected by the polyclonal IRMA.

Antibodies, Monoclonal↗

PubMed1992

Developmental changes in 24-hour profiles of luteinizing hormone and follicle-stimulating hormone from prepuberty to midstages of puberty in boys.

To establish the pubertal changes in gonadotropin secretion, 24-h secretory profiles of LH and FSH were studied in 10 healthy boys by ultrasensitive (sensitivity, 0.019 and 0.014 IU/L, respectively) time-resolved immunofluorometric assays 21 times. Five of the 10 boys were sampled on 2-6 occasions over a time interval of 0.95-6.4 yr. When sampled, 6 boys were prepubertal (testicular volume, less than 3 mL), 8 boys were early pubertal (testicular volume, 3-5 mL), and 7 boys were midpubertal (testicular volume, 10-25 mL). Plasma was taken every 20 min for 24 h. All boys had LH and FSH pulses. In prepuberty, the mean LH level was much lower than the mean FSH level, and neither showed significant diurnal variation. In early puberty, the mean LH level increased much more than that of FSH. For LH, the increase in mean levels was due to an increase in both pulse amplitude and frequency. During early and midpuberty, these changes were most marked at night, leading to the appearance of diurnal variation. For FSH, the mean levels increased progressively from prepuberty to midpuberty, with a slight increase in the mean pulse amplitude at the onset of puberty, whereas no change in pulse frequency was found. In contrast to LH, no diurnal variation was found for FSH at any of the pubertal stages. Thus, at the onset of puberty, gonadotropin secretion undergoes specific changes, which are different for LH and FSH, involving changes in pulse amplitudes and frequencies and development of diurnal variation for LH.

Adolescent↗

PubMed1992

Reproducibility of 24-h growth hormone profiles in children.

The rate of GH secretion and the pattern of GH peaks were compared in a group of nine prepubertal children during their prepubertal period in repeated 24-h GH profiles. At investigation, the children were 6-13 years old (at first profile 6-11 years old) and of normal height (+/- 2 SD). Two profiles were obtained per child, (with a mean time interval of 1.5 years, range 0.7 to 3.5 years. The calculated GH secretions of the first and second profiles were compared. As a group, no significant differences in secreted amount of GH, when expressed as data from the second profile as a percentage of data from the first profile (93 +/- 8%), number of peaks (98 +/- 7%) or mean peak amplitudes (92 +/- 11%), were obtained. Between the repeated curves of an individual child, maximal difference in secretion, number of peaks and mean peak amplitudes ranged around +/- 30%, with a mean intraindividual cv of 12%. The reproducibility in the peak distribution for all profiles was also analysed. The relative frequencies is a percentage of the GH peak amplitudes and peak widths were virtually identical in the repeated profiles. Reproducibility of the temporal pattern of profiles was analysed using time-series analysis (Fourier analysis) and showed no difference in rhythmicity between the different occasions. In conclusion, a high reproducibility of both GH secretion and GH pattern was found for the whole group of prepubertal children.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

PubMed1989

Adenosine as substrate and receptor agonist in the ovary.

In the present study the possible dual effects of adenosine as substrate and adenosine receptor agonist in rat granulosa cells, cumulus-oocyte complexes, luteal cells and ovarian membranes are discussed. Adenosine is an indispensable compound in cell energy metabolism, as precursor to cofactors, second messenger and nucleic acids. Adenosine is also an agonist to adenosine receptors. The adenosine receptor can either inhibit (A1) or stimulate (A2) adenylate cyclase. Alternatively, in some cells adenosine receptor activation is linked to other cellular events like inhibition of Ca2+ fluxes. Adenosine is taken up by isolated preovulatory granulosa and luteal cells from pregnant mare serum gonadotropin-treated immature rats, but follicle stimulating hormone (FSH) decreases the uptake by granulosa cells. Adenosine, but not the non-metabolizable adenosine analogs 5'-(N-ethyl)carboxamide-adenosine (NECA), 2-chloro-adenosine (2-Clado), N6-(R-phenyl-isopropyl)-adenosine (R-PLA) and N6-(S-phenyl-isopropyl)-adenosine (S-PLA), increase granulosa cell ATP levels. FSH and luteinizing hormone (LH) decrease granulosa cell ATP levels in the presence or absence of adenosine. It has previously been shown that FSH and LH decrease oxygen consumption by cumulus-oocyte complexes and increase their lactate production. These effects have been suggested to be due to a competition of cofactors (e.g. ADP) common to glycolysis and the respiratory chain. The fact that adenosine reverse the gonadotropin-induced effects on oxygen consumption and lactate production support this theory. Adenosine and its analogs increase cAMP accumulation in luteal and granulosa cells only in the presence of gonadotropins, and this effect is antagonized by the adenosine receptor antagonist 8-phenyl-theophylline (8-PHT). Furthermore, adenylate cyclase is stimulated by adenosine analogs in membranes from non-luteinized and luteinized ovarian membranes and in luteal cell homogenates. The effect of NECA is antagonized by 8-PHT. In the membranes, the rank order of potency was NECA greater than 2-Clado greater than R-PLA greater than S-PLA, suggesting adenosine A2 receptors. In summary, it is suggested that adenosine can act both as a substrate to intracellular metabolism and as an adenosine A2 receptor agonist in granulosa and luteal cells. A paracrine short loop positive feedback model is proposed where extracellular adenosine, derived from a gonadotropin-induced extracellular increase in cAMP and a decrease in cellular ATP, enhances gonadotropin stimulation in granulosa and luteal cells.

Adenosine↗

PubMed1989

Growth hormone secretory rates in children as estimated by deconvolution analysis of 24-h plasma concentration profiles.

The kinetics of growth-hormone (GH) distribution and elimination was estimated in five GH-deficient children who received 11 intravenous single injections of GH. The plasma disappearance data were analyzed in terms of a two-compartment model. The kinetic parameters obtained were then used in calculating the GH-secretory rate by a numerical deconvolution technique. A simple formula was derived for calculation of the cumulated secretion from the area under the concentration curve of 145 healthy children of various ages, heights, and stages of puberty. The estimated 24-h GH secretion increased with age, corresponding to a two- to fourfold increase during the adolescence period. The highest secretions were found in pubertal stages 3-4. In prepubertal children the heights correlated markedly with the secretion of GH (r = 0.83). Thus an indication of the range of the GH secretion in normal growing children is found, which is important to estimate substitution doses for treatment of GH-deficient children.

Activity Cycles↗

PubMed1989

Plasma growth hormone profile in acromegaly before and ten days after transsphenoidal surgery.

Profiles of plasma GH, plasma somatomedin-C and serum PRL concentrations as well as serum GH response to iv TRH were determined in 11 patients with acromegaly before and 10 days after surgery. Blood for profile determinations was drawn from a peripheral vein with a continuous withdrawal pump changing the recipient tube at 30-min intervals. Before surgery all patients had high plasma GH concentrations with irregular peaks and somatomedin-C concentrations were elevated. The response to TRH was abnormal in 8 patients. Three patients had slightly elevated PRL concentrations and one had high PRL concentration (6900 mU/l). Ten days after surgery GH concentrations were still high in 2 patients (greater than 5 mU/l), as were somatomedin-C concentrations (3.2 and 2.4 U/l, respectively). In 3 patients basal GH concentrations were less than 5 mU/l and somatomedin-C concentrations were normal, but there were no major peaks in plasma GH concentrations. In 2 patients major peaks in GH concentrations appeared after surgery, but basal GH concentrations were 1.9 and 0.95 mU/l, respectively. One patient with hyperprolactinemia still had slightly elevated PRL concentration (486 mU/l), but the response to TRH was normalized. Finally, in 4 patients, mean GH concentrations were markedly reduced, somatomedin-C concentrations normalized and apparently normal plasma GH profiles appeared with low or undetectable basal levels separating major peaks. The results indicate that in some patients with acromegaly apparently normal GH secretion can be demonstrated 10 days postoperatively. Characterization of circadian GH rhythms during the early postoperative stage may contribute to the evaluation of the effect of surgery.

Acromegaly↗

PubMed1989

Beta-adrenergic receptor concentration and subtype in the corpus luteum of the adult pseudopregnant rat.

Luteal beta-adrenergic receptor concentration and subtype were determined in adult pseudopregnant rats during and after the period of the functional luteal phase. The specific beta-adrenergic receptor ligand (-)-3-[125I]iodocyanopindolol ([125I]ICYP) was used to determine the receptor concentration in corpora lutea of adult pseudopregnant rats. A 3-fold increase in beta-adrenergic receptor concentration was seen during the first 2-3 days of pseudopregnancy, whereafter the receptor concentration declined. During the functional luteal regression period (Day 12-15) the receptor levels were still low. In regressed (Day 16-22) corpora lutea a temporary increase in beta-receptor concentration was seen which may represent some role for beta-adrenergic mechanisms in the regulation of morphological regression in the corpus luteum. To determine the beta-adrenergic subtype, competition of [125I]ICYP-binding with selective beta 1- and beta 2-adrenergic antagonists was assessed in corpora lutea of different ages and in rat heart and uterus. The beta-adrenergic receptors in corpora lutea of adult pseudopregnant rats were shown to be solely of the subtype beta 2, regardless of the luteal age.

Animals↗

PubMed1989

Differential sensitivity to cAMP among human cord and maternal/adult peripheral lymphocytes discloses differences between PHA- and OKT3-induced activation pathways.

Previous studies have demonstrated that human cord blood lymphocytes are resistant to the anti-proliferative action of prostaglandin E2 (PGE2) in phytohaemagglutinin (PHA)-induced mitogenesis, whereas the same cells activated by OKT3 are at least as sensitive to PGE2 as the corresponding cells from their mothers or other adults. In the present investigation it was found that: (i) PHA-induced proliferation of cord peripheral blood mononuclear leucocytes (PBML) is less sensitive to inhibition by forskolin--a direct activator of adenylate cyclase (AC)--and dibutyryl cAMP--a permeant cAMP analogue--than the proliferation of the corresponding maternal cells; (ii) OKT3-induced proliferation of cord as well as maternal PBML is highly sensitive to inhibition by forskolin and dibutyryl cAMP; (iii) cord PBML show an overall lower rate of AC activity compared with maternal PBML, in response to PGE2 and other autacoids as well as to receptor-independent stimulation; (iv) cord PBML also display a significantly lower rate of degradation of cAMP through cAMP-phosphodiesterase compared with maternal cells; (v) unbroken cord and maternal PBML show comparable rates of cAMP accumulation after stimulation with PGE2. The results suggest a lower sensitivity to the effect of cAMP in cord compared with maternal/adult lymphocytes in PHA-induced proliferation. Moreover, the data illustrate differences between PHA- and OKT3-mediated activation pathways, as well as differences in cell regulation mechanisms between cord and maternal PBML.

3',5'-Cyclic-AMP Phosphodiesterases↗

PubMed1988

Evidence for A2 adenosine receptor-mediated effects on adenylate cyclase activity in rat ovarian membranes.

Effects of adenosine analogues on adenylate cyclase activity in preovulatory rat ovarian membranes were studied. Adenosine analogues stimulated adenylate cyclase activity in the following rank order of potency: NECA (5'-(N-ethyl)carboxamidoadenosine) greater than 2-chloroadenosine greater than N6-(R-phenylisopropyl)-adenosine greater than N6-(S-phenylisopropyl)adenosine. The apparent EC50 for NECA was 0.28 microM. The adenosine receptor antagonist 8-phenyltheophylline (10 microM) displaced the dose-response curve for NECA to the right, increasing the EC50 for NECA about one order of magnitude. NECA also additively increased maximally FSH-stimulated adenylate cyclase activity. These results suggest that adenosine stimulates adenylate cyclase in rat ovarian membranes via adenosine receptors of the A2 type.

Adenosine↗

PubMed1988

Adenosine receptor-mediated effects by nonmetabolizable adenosine analogs in preovulatory rat granulosa cells: a putative local regulatory role of adenosine in the ovary.

The influence of nonmetabolizable adenosine analogs on cAMP production was investigated in preovulatory rat granulosa cells. 5'-(N-ethyl)Carboxamido-adenosine (NECA), a stimulatory A2-adenosine receptor agonist, stimulated cAMP accumulation, and NECA and 2-chloro-adenosine also potentiated the response to FSH. The adenosine receptor antagonist 8-phenyltheophylline antagonized the effect of NECA, shown by a shift in the dose-response curve to the right. The stimulatory effect of NECA was also seen in an ovarian membrane preparation, where NECA stimulated adenylate cyclase in both the presence and absence of FSH. The stimulatory effect of NECA was also decreased by 8-phenyltheophylline in this preparation. The A1-receptor agonists N6-(R-phenyl-isopropyl)-adenosine (R-PIA) and N6-(S-phenyl-isopropyl)-adenosine (S-PIA) both inhibited FSH-stimulated cAMP accumulation. The inhibitory effects of R-PIA and S-PIA, but not the stimulatory effects of NECA, could be counteracted by dipyridamole, a nucleoside transport inhibitor. Furthermore, R-PIA and S-PIA inhibited adenosine uptake into granulosa cells. Thus, the inhibitory effects of R-PIA and S-PIA are not likely to be mediated via membrane-bound inhibitory A1-adenosine receptors. Neither the stimulatory effects of NECA nor the inhibitory effects of R- and S-PIA could be attributed to changes in ATP levels, since the ATP levels were unaffected by these analogs. The results of this study indicate the existence of stimulatory A2-adenosine receptors in preovulatory rat granulosa cells and suggest a membrane-associated modulatory role of adenosine in preovulatory granulosa cells.

2-Chloroadenosine↗

PubMed1988

Analyses of 24-hour growth hormone profiles in children: relation to growth.

The relationship between height and amount of GH measured during a 24-h period was studied in 127 children who were growing at different rates. Of the children, 88 were prepubertal (3-16 yr old) and 39 were pubertal (10-16 yr old). The height of each child was expressed as the SD score, i.e. height in relation to the sex- and age-matched Swedish reference groups, and spontaneous GH secretion was estimated by taking integrated 20-min blood samples for a 24-h period, i.e. 72 samples/child. In a few children, discrete samples were taken in parallel with the integrated 20-min samples with virtually the same results. Plasma GH was estimated in each sample using a polyclonal RIA method. To compare different 24-h GH profiles, the profiles were analyzed using a computer program (Pulsar). One objective of the study was to determine if less frequent sampling and/or shorter sampling periods yielded the same information as that obtained by 20-min sampling for the whole 24-h period. To determine if less frequent sampling provided the same information as that obtained by the 20-min period, we simulated 40- and 60-min periods by pooling two or three consecutive samples. No difference was found between 20- and 40-min sampling, but with 60-min sampling the mean calculated baseline plasma GH concentrations increased, and the GH concentration within peaks [the area under the curve above the baseline (AUCb)] decreased markedly. A 30-min sampling interval thus seems to be a valid practical compromise. To determine if sampling periods shorter than 24 h provided the same information, we divided the profiles, which started at 0900 h, into two 12-h, three 8-h and four 6-h periods. A graded decrease in AUCb and a corresponding increase in the baseline was found with the shorter periods, indicating that the whole 24-h period is necessary for GH sampling. Another objective of the study was to determine whether there was a correlation between 24-h GH secretion and the height, age, and sex of the children. In the prepubertal children, the height (in SD scores) was highly correlated (r = 0.69; P less than 0.001) with GH AUCb during the 24-h period. Height also correlated with AUCb estimated over shorter time periods; the correlation diminished with decreasing time. In the pubertal children, a nonlinear correlation (r = 0.36; P less than 0.05) was found between height and 24-h GH (AUCb).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1987

Catecholamine content and adenylate cyclase activity in corpora lutea of different ages of the PMSG-treated immature rat.

The catecholamine content and adenylate cyclase response were studied in a well-characterized corpus luteum model, where ovulation was induced by treatment of prepubertal Sprague-Dawley rats with pregnant mare's serum gonadotropin. The luteal content of noradrenaline, determined with HPLC, was constant during the first 7 days of pseudopregnancy, followed by a 3-fold increase in older corpora lutea. No detectable amounts of dopamine were found, while trace amounts of adrenaline were found in a few cases. The increase in noradrenaline content was not associated with a changed sensitivity of luteal adenylate cyclase to catecholamines. The response to adrenaline was maximal in 3-day-old corpora lutea, whereafter a decrease was seen. The significance of the increased endogenous levels of noradrenaline at the end of pseudopregnancy is at present unknown. However, the fact that the increase in noradrenaline occurs a few days before spontaneous luteolysis is of special interest, since it has been suggested that an adrenergic innervation is a prerequisite for the antigonadotropic effect of prostaglandin F2 alpha in the human corpus luteum.

Adenylyl Cyclases↗

PubMed1987

A phorbol ester, phorbol 12-myristate 13-acetate, and a calcium ionophore, A23187, can mimic the luteolytic effect of prostaglandin F2 alpha in isolated rat luteal cells.

To explore the possible role of protein kinase C and calcium in the luteolytic process, we treated luteal cells with a protein kinase C activator, the phorbol ester, phorbol 12-myristate 13-acetate (PMA), and with the calcium ionophore, A23187. Lower concentrations of PMA could clearly mimic the inhibitory, luteolytic effects of prostaglandin F2 alpha (PGF2 alpha) on LH-induced cAMP and progesterone production. A nontumor promoting phorbol ester, 4 alpha-phorbol 12,13-didecanoate, had no inhibitory effect, indicating a specific PMA effect. The calcium ionophore, A23187, also gave a marked inhibition of LH-induced cAMP and progesterone production. Hormone-stimulated adenylate cyclase activity was markedly impaired after preincubation of the cells with PGF2 alpha, PMA, or A23187, but no effect was seen when the substances were added to isolated membranes. In addition, the stimulation of progesterone production in the luteal cells with the cAMP analogs, 8-bromo-cAMP and (Bu)2cAMP, was almost totally abolished when PMA or A23187 was present. We conclude that PMA and A23187 in many ways mimic the effect of PGF2 alpha in luteal cells. The inhibition of steroidogenesis is partly dependent on depressed activity of the hormone-sensitive adenylate cyclase, but also obtained by inhibiting steps distal to cAMP formation. Both points of action seem to be calcium and/or protein kinase C dependent. In contrast, higher concentrations of PMA markedly stimulated steroidogenesis without affecting the cAMP level, a stimulation not seen after incubation with 4 alpha-phorbol 12,13-didecanoate, suggesting again a specific PMA effect. The stimulation of steroidogenesis by higher concentrations of PMA seems to be specific, but the interpretation of this finding is unclear at present. In conclusion, PMA and A23187 mimic some of the luteolytic properties of PGF2 alpha, not only inhibiting the luteal cAMP system, but also by inducing lesions in the steroidogenic steps beyond the cAMP system.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1987

Studies of the luteinization process in the rat: follicular and luteal adenylate cyclase responsiveness to catecholamines.

The subject of the study was the development of follicular and luteal catecholamine responsiveness during the periovulatory period. Follicles and corpora lutea and granulosa cells were obtained from the PMSG ovulatory model and adenylate cyclase activity measured in membrane fractions. In the earlier part of the follicular phase (48 h and 26 h before ovulation) no response to noradrenalin on follicular and granulosa cell adenylate cyclase activity was seen. A small but significant response to noradrenalin was observed from 18 h before until 3 h after ovulation. The response to noradrenalin on luteal adenylate cyclase activity increased markedly with time and reached a maximum 39-57 h after ovulation. After this time the luteal response to noradrenalin decreased with luteal age. The effect of LH was less than that of noradrenalin during the early luteal phase, and in contrast to noradrenalin, increased with luteal age. The combined effects of LH and noradrenalin were not additive. In order to test whether gonadotropins could induce a noradrenalin response, injections of LH and FSH were given to the animals two days before ovulation. LH, but not FSH, induced a small but significant response to noradrenalin 16 h later. The present investigation has shown that ovarian responsiveness to catecholamines appears in preovulatory follicles followed by a marked increase in luteal catecholamine responsiveness. This development could at least partly occur under the influence of LH.

Adenylyl Cyclases↗

PubMed1986

Mechanism of action of prostaglandin F2 alpha-induced luteolysis: evidence for a rapid effect on the guanine nucleotide binding regulatory component of adenylate cyclase in rat luteal tissue.

The initial events in prostaglandin F2 alpha-(PGF2 alpha)-induced luteolysis were studied in pregnant mare serum gonadotropin/human chorionic gonadotropin-(PMSG/hCG)-treated rats with luteinized ovaries. Injection with a potent PGF2 alpha analog (cloprostenol, 5 micrograms/ml) induced functional luteolysis, as assessed by plasma levels of progesterone and 20 alpha-dihydroprogesterone. At 0.5 and 3 h after cloprostenol administration the luteolytic effect was also evident as a reduced response of luteal adenylate cyclase to all stimulatory agents tested, LH, isoproterenol, fluoride, guanylylimidodiphosphate and forskolin. 24 h after cloprostenol the response to all agents, except to LH, had returned to normal. This general and transient block of the luteal adenylate cyclase system indicates that a common factor, possibly the stimulatory guanine nucleotide binding protein (Ns), is involved in the mechanism of action of PGF2 alpha. To test this hypothesis, we measured the functional coupling of the Ns protein to the beta-adrenergic receptor in luteal membranes. Binding competition curves showed a marked shift to the right in membranes prepared from rats injected with cloprostenol 0.5 and 3 h before membrane preparation, while at 24 h after cloprostenol the shift had disappeared. The total number of beta-adrenergic receptors was, however, not affected by the cloprostenol treatment. Computer analysis of the data indicates that, at 0.5 and 3 h after cloprostenol treatment, there was a reduced number of high affinity binding sites, 38 and 41%, respectively, compared to 53% for control membranes. The cellular mechanism for this action of PGF2 alpha on the Ns protein remains to be elucidated.

Adenylyl Cyclases↗

PubMed1986

Gonadotropin depression of adenosine triphosphate levels and interaction with adenosine in rat granulosa cells.

Cellular ATP levels were measured with the luceferin-luciferase enzyme method in incubated preovulatory granulosa cells in vitro from PMSG-treated immature rats. The ATP levels were depressed by both FSH and LH, FSH being the more effective. Adenosine enhanced the ATP levels about 3-fold, but the depressive effects of gonadotropins could not be overcome by the addition of adenosine. Uptake of adenosine in granulosa cells followed Michaelis-Menten kinetics, with a Km of 15.9 +/- 3.6 microM and a maximum velocity of 1.6 +/- 0.1 pmol/min X 10(5) cells. The half-time for uptake of adenosine was about 40 min. The maximal uptake of adenosine was lowered from 48 +/- 5 to 30 +/- 1 pmol/10(5) cells by FSH treatment of the cells. The basal secretions of cAMP and progesterone from the granulosa cells were slightly but significantly enhanced by adenosine alone. Adenosine markedly enhanced FSH-stimulated cAMP secretion, but not progesterone secretion. A nonmetabolizable adenosine analog, 2-chloro-adenosine, did not affect the ATP levels or the secretion of cAMP from granulosa cells. This study confirms previous observations that adenosine can increase ATP levels and amplify the response to gonadotropins in gonadal cells. A novel finding is that the levels of ATP in granulosa cells are markedly depressed by gonadotropins. It is speculated that this depression of ATP may be a factor in the metabolic control of granulosa cells.

Adenosine↗

PubMed1986

Adenylate cyclase activity in rat corpora lutea evidence for a rapid development of the regulatory Ns-protein.

Adenylate cyclase activity was studied in membranes from isolated corpora lutea of defined ages obtained from pregnant mare's serum gonadotropin treated rats and the effects of luteinizing hormone (LH), isoproterenol, guanylylimidodiphosphate (Gpp (NH)p), fluoride and forskolin were compared. The effect of LH on adenylate cyclase activity increased with the luteal age up to nine days of age, while the effect of isoproterenol increased dramatically during the first days, reaching a maximum at 2-3 days of age and then declined. Forskolin potentiated the effects of both LH and isoproterenol without affecting the patterns of age-dependency. The effect of forskolin itself was fairly constant during the luteal phase, indicating a relatively constant amount of the catalytic unit in the corpus luteum. The effects of fluoride and Gpp(NH)p on the other hand increased markedly during the first days and then remained constant for the rest of the period studied. These results suggest that the regulatory Ns-protein develops during the first days of luteal life. It is speculated that the close correlation between the development of beta-adrenergic response and the development of Ns-protein are causally related.

Adenylyl Cyclases↗