Biomedical subjects

G Selstam

Publications and source records attributed to G Selstam.

At least 19 recordsLinked to original sources

PubMed2005

Prostaglandins of the E-series inhibit connective tissue proliferation in the liver wound of the rat.

The present study was undertaken to relate wound healing of an internal organ to prostaglandins of the E and F series. A small liver wound was induced by a galvanic cauter via the abdominal route under general anesthesia and prostaglandin E1, E2 and F2alpha were injected twice daily at a dose of 250 microg/kg. Proliferation of the connective tissue in the liver wound was estimated morphometrically 6 days after liver wound infliction. Levels of prostaglandins E2 and F2alpha were measured in the liver wound as well as in normal liver tissue from adjacent lobes using radioimmunoassay. The results show that exogenous prostaglandins of the E-series suppress connective tissue proliferation. Three minutes after the last prostaglandin E2 injection, high prostaglandin concentrations were measured both in the liver wound and in the liver tissue of the adjacent lobe. Prostaglandin F2alpha injections had no effect on wound healing. We believe that the rat thermic liver wound model can be used for different studies on wound healing mechanisms and that prostaglandins of the E-series are involved in wound healing in the specific time period studied.

Alprostadil↗

PubMed2000

Lipoic acid prevents suppression of connective tissue proliferation in the rat liver induced by n-3 PUFAs. A pilot study.

As previously shown, dietary n-3 polyunsaturated fatty acids (n-3 PUFAs) suppress connective tissue proliferation in the rat liver wound concurrent with an elevated level of lipid peroxidation. The present study was undertaken to investigate the influence of alpha-lipoic acid (LA), a natural anti-oxidant, on these effects of n-3 PUFAs. Rats were fed with a commercial pellet diet (control group) or with diets enriched with 10% of sunflower oil (n-6 group) or 10% of fish oil (n-3 group) for 8 weeks followed by addition of LA to the same diets for 10 days. Then a liver thermic wound was induced and the administration of LA was continued for 6 days. The proliferation of the connective tissue, the level of lipid peroxidation and their peroxidizability and the content of prostaglandins E2 and F2alpha were measured in the liver wounds. LA prevented the suppression of connective tissue proliferation in the healing wound induced by n-3 PUFAs, avoided the increase in peroxidation of lipids, reduced peroxidizability of lipids and modulated the decrease in PGE2 and PGF2alpha. The results indicate that dietary LA may prevent the suppression of liver wound healing induced by n-3 PUFAs.

Animals↗

PubMed1998

Luteolysis induced by a prostaglandin F2alpha analogue occurs independently of prolactin in the rat.

The hypothesis that prolactin exerts a stimulatory dominance over the luteolytic effect of prostaglandin (PG) F2alpha on corpus luteum maintenance and progesterone production was experimentally tested. A dose-dependent effect of the stable PGF2alpha analogue cloprostenol (dose range 200 ng(-5) microg) was found 12 h after s.c. injection, in Day 9 adult pseudopregnant rats: 1) LH receptor mRNA levels, as measured by RNase protection assay, were dramatically decreased (by 67%) by a single s.c. dose of 200 ng cloprostenol; and 2) serum progesterone levels were significantly (p < 0.05) decreased (by 43%) whereas 20alpha-dihydroprogesterone significantly (p < 0.05) increased (by 80%) initially at a 0.5-microg dose of cloprostenol. To study the integrated response to prolactin and PGF2alpha, we investigated the effect of cloprostenol treatment in sterile-mated female rats with or without circulating prolactin. Prolactin secretion was inhibited by s.c. injection of bromocriptine (1 mg) in the morning of the ninth day of pseudopregnancy. A group of rats was left prolactin-depleted; in another group prolactin was reintroduced by adding 8 IU ovine prolactin. It was found that after injection of 0.5 microg cloprostenol the LH receptor mRNA levels and the serum progesterone/20alpha-dihydroprogesterone ratio were not significantly different whether the rats had circulating endogenous/exogenous prolactin or were prolactin-depleted. Therefore, although prolactin exerts a stimulatory influence on both progesterone production and corpus luteum LH receptor gene expression, the conclusion is reached that prolactin alone cannot antagonize the luteolytic effect of PGF2alpha.

Animals↗

PubMed1997

Twenty-four-hour profiles of luteinizing hormone, follicle-stimulating hormone, testosterone, and estradiol levels: a semilongitudinal study throughout puberty in healthy boys.

To follow and correlate gonadotropin and sex steroid changes throughout puberty, 24-h profiles of LH, FSH, testosterone, and estradiol were taken on several occasions for between 2-9.5 yr in 12 healthy boys, aged 8.7-18.2 yr. Serum concentrations of LH and FSH were measured every 20 min, whereas testosterone and estradiol were measured every 2-4 h during the 24-h period. The prepubertal boys (Tanner stage 1) were subdivided into two groups: Pre 1, with a testicular volume of 1-2 mL, and Pre 2, with a testicular volume of 3 mL. Pubertal stages were classified, according to testicular volume, as early puberty (pubertal stage 2; 4-9 mL), midpuberty (pubertal stages 3-4; 10-15 mL), and late puberty (pubertal stage 5; > or = 16 mL). Mean levels of LH and FSH increased with pubertal development, although the increase in LH was greater than that in FSH. These increases were due to elevated basal levels of LH and FSH as well as to increases in the number of peaks and the peak amplitudes of LH. No diurnal rhythm was found in boys at stage Pre 1. Thereafter, a clear diurnal rhythm appeared for LH, and later in puberty, an ultradian rhythm was superimposed, as shown by time-sequence analyses. A diurnal rhythm also existed for FSH, but was much less marked than that for LH despite a clear covariation between LH and FSH, as shown from cross-correlation studies. Testosterone also showed diurnal variations from the late prepubertal stage, followed by increasing levels during both day and night in puberty. We conclude that during puberty, gonadotropin levels rise differently for LH and FSH, which may be due to the development of differences in feedback mechanisms. Despite covariation between LH and FSH, only LH showed a clear diurnal variation. In parallel, nocturnal variations in testosterone and estradiol were found. Changes in mean levels of LH, testosterone, and estradiol as well as their mean daytime and nighttime levels follow each other from the prepubertal stages to late puberty.

Child↗

PubMed1996

Characterization and regulation of a mRNA encoding the prostaglandin F2alpha receptor in the rat ovary.

The recent cloning of several cDNAs encoding prostaglandin (PG) receptors has paved the way for a more detailed investigation of the postulated regulatory role of prostaglandins in corpus luteum function. We have utilized the reverse transcription-polymerase chain reaction (RT-PCR) to isolate a mRNA encoding the ovarian PGF(2alpha) (FP) receptor, using oligonucleotides based on the recently cloned mouse cDNA as primers. The 5'-untranslated region of the rat ovarian mRNA was isolated following 5'-RACE (rapid amplification of cDNA ends). The isolated 1526 base-pair sequence, which spans the entire open reading frame, was found 100% identical in the protein coding region to a similar sequence isolated from a rat astrocyte cDNA library, but different in the first 32 nucleotides of the 5'-untranslated region, possibly due to tissue-specific splicing heterogeneity. Using ribonuclease protection assay, a quantitative analysis of FP receptor mRNA levels was performed in corpora lutea excised from adult pseudopregnant rats (Day 8) at different timepoints (0.5-48 h) following the in vivo s.c. regimen of a luteolytic dose of the FP receptor agonist cloprostenol (5 microg). Already 3 h after cloprostenol injection, FP receptor mRNA levels exhibited a pronounced increase to values 4.0-fold higher (P < 0.01) than before injection. At 7 h through 24 h, the amount of luteal FP receptor mRNA decreased, approaching preinjection levels, whereafter they were again 3.0-fold higher (P < 0.01) at 48 h than before injection. We conclude that following homologous stimulation of the FP receptor, abundance of this mRNA is tissue-specifically regulated in a dynamic pattern, suggestive of an important role for FP receptor-mediated action on gene expression during the demise of corpus luteum function.

Amino Acid Sequence↗

PubMed1996

Rat luteinizing hormone receptor messenger ribonucleic acid expression and luteolysis: inhibition by prostaglandin F2 alpha.

To elucidate the mechanisms by which prostaglandin F2 alpha (PGF2 alpha) permanently inhibits LH-dependent steroidogenesis during luteolysis, we investigated the effect on luteal LH receptor mRNA levels of the stable PGF2 alpha analogue cloprostenol injected into adult pseudopregnant rats on different days during the luteal period. After treatment, LH receptor mRNA expression was determined by RNase protection assay. Twelve hours after cloprostenol injection on Day 8 of pseudopregnancy, the luteal LH receptor mRNA levels were drastically reduced (0.95 +/- 0.18 fmol mRNA/microgram DNA, p < 0.01) as compared with those in untreated controls (12.3 +/- 1.3 fmol mRNA/microgram DNA) or in corresponding controls given an injection of saline (8.8 +/- 0.7 fmol mRNA/microgram DNA) (n = 6-8 per group). At 24 h the levels rose to 4.3 +/- 0.8 fmol mRNA/ microgram DNA but were still significantly decreased compared to control values. Forty-eight hours after cloprostenol injection, the luteal LH receptor mRNA levels were not significantly different from control levels; but if the rats received an injection every twelfth hour, levels were significantly decreased compared to those in controls. When PGF2 alpha was injected, LH receptor mRNA levels were reduced in the same manner as seen after cloprostenol injection. LH receptor mRNA of young corpora lutea (CL) (Day 3) was more resistant to down-regulation by cloprostenol than that of CL of the mid (Day 8)-or late (Day 11) luteal phase. On the eighth day of pseudopregnancy, serum progesterone levels were decreased at 0.5 h after cloprostenol injection and fell further at 3 h; serum 20 alpha-dihydroprogesterone levels were first increased at 7 h after cloprostenol injection. We conclude that luteal LH receptor mRNA expression is under direct regulatory control by PGF2 alpha in a both time-and dose-dependent manner and thereby may decisively contribute to the inhibition of LH responsiveness during luteolysis.

20-alpha-Dihydroprogesterone↗

PubMed1996

Coordinated expression of tissue-type plasminogen activator and plasminogen activator inhibitor type 1 during corpus luteum formation and luteolysis in the adult pseudopregnant rat.

Proteolytic activity generated by the plasminogen activator (PA) system is associated with many biological processes. Using an adult pseudopregnant rat model, we have studied how two components of the PA system, tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1), are expressed temporally and spatially during different developmental stages of the corpus luteum (CL). Northern blot analysis, in situ hybridization, in situ zymography, and fibrin overlay were used to analyze the expression and distribution of tPA and PAI-1 messenger RNA (mRNA) as well as PA activity in CL of different ages. We demonstrated that during the luteinization period (approximately days 1-2), tPA mRNA was highly and evenly expressed in newly formed CL, whereas PAI-1 mRNA was mainly detected in the central part of the same CL. In accordance with these findings, proteolytic activity generated by tPA was detected in the outer region of newly formed CL by in situ zymography. During the luteotropic period (approximately days 3-10), tPA mRNA expression was very low. PAI-1 mRNA expression was also low, but increased on day 10. As expected, proteolytic activity was very low during this period. During functional luteolysis (days 13-14) and subsequent structural luteolysis, tPA mRNA was elevated. PAI-1 mRNA was also expressed during this period. Moreover, the net PA activity, as determined by fibrin overlay, was relatively high during this period. Our studies indicate that tPA and PAI-1 are coordinately expressed in the CL, resulting in increased proteolytic activities during the luteinization and luteolytic periods. PA-mediated proteolysis may, therefore, play a role in both CL formation and luteolysis in rats.

Animals↗

PubMed1995

Presence of the intermediate filaments cytokeratins and vimentin in the rat corpus luteum during luteal life-span.

The presence of the intermediate filament (IF) proteins cytokeratins and vimentin in corpus luteum (CL) and other parts of the ovary from adult pseudopregnant rats was investigated using immunohistochemistry and immunoblot analysis. To induce pseudopregnancy, female rats were mated with sterile male rats. The mating procedure induces a prolonged luteal life-span of 13 +/- 1 days. Positive staining for cytokeratin could be seen in CL, in the theca layer of follicles, and the ovarian surface epithelium with the broad-spectrum monoclonal antibody cocktail AE1/AE3. Weak staining was also seen in CL with antibodies against cytokeratins 8 and 18. A similar distribution was also seen for vimentin, which furthermore was detected in blood vessels. No changes in staining intensity was seen in CL of different luteal age. The strong staining for vimentin in CL was confirmed by immunoblot analysis, where one main band of 57 kDa was observed from day 1 to day 19 of pseudopregnancy. Expression of the IF proteins investigated seems to start in the newly formed CL and the continuous expression indicates that they are not directly regulated by luteal steroids.

Animals↗

PubMed1995

Interaction between 17 beta-oestradiol and 3 alpha-hydroxy-5 alpha-pregnane-20-one in the control of neuronal excitability in slices from the CA1 hippocampus in vitro of guinea-pigs and rats.

The effect of 17 beta-oestradiol and 3 alpha-hydroxy-5 alpha-pregnane-20-one (allopregnanolone) on the action potentials in the Schaffer collateral pathway was investigated in hippocampus CA1. Slices from male and female guinea-pigs and female rats were used. In the rat three groups were studied: (a) untreated prepubertal rats at day 25 after partus; (b) rats injected on day 26 with 10 IU of equine serum gonadotropin studied on day 28, when in the pro-oestrus follicular phase; and (c) on day 32 when in the luteal phase. The allopregnanolone (12.6 microM, 0.5 nL) was applied locally in stratum orienspyramidale. the 17 beta-oestradiol (0.7 nM) was perfused (4 mL min-1) or applied locally. The amplitude of the population spike in stratum pyramidale was increased by oestradiol in guinea-pigs of both sexes and in all the three groups of rats. Allopregnanolone decreased the amplitude of the population spike in the guinea-pigs and in the luteal phase rats. The effect appeared within seconds after the application of the drugs. The allopregnanolone inhibition of the population spike was increased by perfusion with oestradiol in the guinea-pigs and in the luteal phase rats. This effect appeared within 7 min, and improved with increasing length of the perfusion (7-71 min). It remained for 55 min after return to perfusion with artificial cerebrospinal fluid. In prepubertal and follicular phase rats the allopregnanolone inhibition was seen only after perfusion with oestradiol for more than 15 min. The results show that 17 beta-oestradiol increases the allopregnanolone inhibition and that this inhibition is most efficient during the luteal phase of the rat.

Action Potentials↗

PubMed1995

Ovarian levels of epidermal growth factor receptor mRNA in the rat--a postovulatory decrease.

Members of the epidermal growth factor (EGF) family have many different effects on ovarian cells including a strong inhibition of estradiol-17 beta production. An increased binding of the EGF family to its receptor is seen at the time of ovulation. The aim of the present study was to measure the mRNA levels of the EGF receptor in the preovulatory follicle and to see if the levels are still high after functional luteolysis. The mRNA of the EGF receptor was measured in whole ovaries, follicles and corpora lutea. Pregnant mare serum gonadotrophin (PMSG) stimulated rats were used to get defined follicles. To achieve luteolytic corpora lutea on day 11, the adult female pseudopregnant rat model was used. Determination of the EGF receptor mRNA was performed with solution hybridization analysis, using a 768 bp long probe of the human EGF receptor (2318-3085). A two-fold increase in the mRNA levels of the EGF receptor was registered between 09.00 and 21.00 h during the proestrus day in the preovulatory follicle. Concurrently, serum estradiol-17 beta levels decreased from 420 +/- 65 to 79 +/- 6 pM. High levels of EGF receptor proteins in the preovulatory follicle were verified by immunohistochemistry. The levels of EGF receptor mRNA was decreasing from 25.4 +/- 4.4 fmol mg-1 in the corpus luteum on day 1 to 7.6 +/- 9.9 fmol mg-1 on day 11. Thus, the high amounts of EGF receptor in the ovary during the late preovulatory period might be involved in the regulation of ovarian estradiol-17 beta production.

Animals↗

PubMed1994

Increased LH receptor mRNA and extended corpus luteum function induced by prolactin and indomethacin treatment in vivo in hysterectomized pseudopregnant rats.

To assess the effects of prostaglandins and prolactin on corpus luteum function and regression, sterile-mated adult pseudopregnant rats hysterectomized on day 5 after mating were injected with indomethacin or prolactin. Daily samples of blood were collected via the tail, from day 12 to day 21, and assayed for serum concentrations of progesterone, 20 alpha-dihydroprogesterone and LH, whereafter corpora lutea and the remainder of ovaries were separated and the tissue content of PGF2 alpha, PGE2 and LH receptor mRNA were measured. Injections of prolactin (8 iu) s.c. or a low dose of indomethacin (200 micrograms kg-1) s.c. were administered twice a day, beginning on day 13 after mating. Both indomethacin and prolactin significantly increased serum progesterone concentrations (P < 0.05; n = 8), and extended the period of functional corpora lutea when compared with controls. Indomethacin, but not prolactin, lowered the concentration of serum 20 alpha-dihydroprogesterone. In the corpora lutea of indomethacin-treated animals, collected on day 21, both prostaglandins measured were reduced in concentration by 50% or more, compared with controls (P < 0.05; n = 8), whereas prolactin had no effect. Both prolactin and indomethacin treatment caused a substantial (tenfold) increase in the concentration of LH receptor mRNA, confined solely to the luteal compartment. These findings in vivo provide further evidence for a luteolytic role of locally synthesized prostaglandins in the rat ovary. Furthermore, prolactin can sustain corpus luteum function by exerting a luteotrophic effect during the late luteal phase, as judged by the stimulation of progesterone synthesis and the expression of LH receptors.

20-alpha-Dihydroprogesterone↗

PubMed1993

Steroid production in different parts of malignant and benign ovarian tumors in vitro.

Pieces of ovaries and tumors from 45 patients (19 with malignant epithelial tumors, 14 with benign epithelial tumors, and 12 with normal postmenopausal ovaries) were incubated, and the release of steroid hormones from different parts of the tumors and from the contralateral ovaries was measured. Tumor tissue (mainly tumor cells with a small number of stromal cells), tumor base tissue (more stromal cells than tumor cells), and control ovaries were preincubated in oxygenated 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid-minimum essential medium buffer at 37 degrees C for 30 min followed by a 3-h incubation in fresh, oxygenated medium. Progesterone, androstenedione, testosterone, and estradiol were measured in the medium by radioimmunoassay at the end of the incubation period. Malignant tumors released more progesterone and androstenedione than benign tumors or postmenopausal control ovaries. In contrast, benign tumors released more testosterone than malignant tumors or control ovaries. Release of estradiol was low and not significantly different among control ovaries and malignant and benign tumor tissue. Different parts of the tumors differed in steroid hormone release. Tissue samples containing more tumor cells than stromal cells released more progesterone than those with predominantly stromal cells. Thus, malignant tumors had an active steroid secretion. Progesterone was the main steroid released.

Adult↗

PubMed1993

Changes in the ovarian intermediate filament desmin during the luteal phase of the adult pseudopregnant rat.

The occurrence of the intermediate filament desmin in ovary and corpus luteum of pseudopregnant rats was studied using Western blot analysis and immunohistochemistry. The luteal phase was induced by mating with vasectomized male rats and ovaries were studied after 6, 11 and 19 days. The findings from the Western blot analysis showed that desmin was present in the corpus luteum. Immunohistochemical localization of desmin showed two types of localization in the corpus luteum. The arteries around the corpus luteum, as well as arteries elsewhere in the ovary, had a high content of desmin in their muscle layer. Dispersed in the corpus luteum was an immunohistochemical staining of desmin that was localized mainly adjacent to the luteal cells. In the other part of the ovary a weak staining was registered in the theca layer, no staining in the granulosa layer and a streaky staining in the hilar region of the ovary. Desmin filaments are found in muscle cells of all types, including vascular smooth muscle cells. Probably, all desmin in the ovary is localized to smooth muscle cells with the possible exception of the corpus luteum where very few muscle cells have been identified. Localization to other vascular cells as endothelial is possible. In this study we found an increase in desmin content in the corpus luteum after day 6. If desmin is related to vascular resistance, our finding is consistent with the decrease in blood flow that occurs after day 6.

Animals↗

PubMed1992

Investigation of the human corpus luteum by ultrasonography: a proposed scheme for clinical investigation.

The corpus luteum was investigated in 18 women undergoing hysterectomy. Preoperative ultrasonography with measurements was performed before the corpus luteum was extirpated, weighed, inspected and the diameters were measured. The concentrations of progesterone and estradiol were also determined in peripheral serum. The ultrasound pictures show that the corpus luteum has a slightly cloudy central part, which can vary from hypoechoic to hyperechoic. The peripheral part (corpus luteum 'wall') has a stronger echo and the maximal and minimal thicknesses can be measured. The results showed correlations between ultrasound measurements and anatomical measurements for wall thickness, outer diameter, inner diameter and wall area of the corpus luteum (n = 12, p < 0.02-0.0001). Moreover, all mid-luteal corpora lutea with a hypoechoic central part (five of 13 women) on ultrasound scan had a cystic central structure. Based on these findings, we suggest that an ultrasound investigation of the corpus luteum in the mid-luteal phase should use the following criteria to classify it into four types. Type a: hypoechoic central part with wall of < 3 mm; type b: hyperechoic central part with wall of < 3 mm; type c: hypoechoic central part with wall of >or= 3 mm; and type d: hyperechoic central part with wall of >or= 3 mm. The finding of a hypoechoic central region with a thin wall (< 3 mm) may indicate corpus luteal insufficiency, since significantly lower serum progesterone levels were found in women with this type of corpus luteum.

Journal Article↗

PubMed1992

Synthesis of prostaglandin F2 alpha, E2 and prostacyclin in isolated corpora lutea of adult pseudopregnant rats throughout the luteal life-span.

The ability of de novo biosynthesis of prostaglandins (PGs) in individual whole corpora lutea (CL) obtained from sterile-mated adult pseudopregnant rats on different days of the luteal phase and the post-luteolytic period was evaluated. Production of PGs, progesterone and 20 alpha-dihydroprogesterone were determined after in vitro incubation of CL extirpated from Day 2 to Day 19 after mating. A time-relationship with increased accumulation of PGs in the medium was demonstrated from 18 s to 5 h, with large increments during the first 30 min. Basal accumulation of PGs in the incubation medium was highest for 6-keto-PGF1 alpha (the stable metabolite of prostacyclin) greater than PGE2 greater than PGF2 alpha greater than thromboxane B2 (TXB2) and basal accumulation of PGF2 alpha and PGE2 measured in the medium was maximal on Day 10-11 of pseudopregnancy, concomitantly with a decline in secretion of progesterone. Addition of arachidonic acid (AA) dose-dependently increased synthesis of PGs, with absolute amounts of PGE2 greater than 6-keto-PGF1 alpha greater than PGF2 alpha greater than TXB2 and addition of 14 microM indomethacin markedly inhibited accumulation of all PGs measured. Luteinizing hormone (LH, 10 micrograms/ml) stimulated progesterone secretion on all days during pseudopregnancy, but not on the post-luteolytic Day 19. LH increased PGF2 alpha, PGE2 and 6-keto-PGF1 alpha secretion on Day 13 of pseudopregnancy by 76%, 91% and 28%, respectively, but not on the other days tested. Furthermore, stimulation of PG-synthesis by addition of AA abrogated the LH-induced progesterone accumulation markedly, but only on Day 13 of pseudopregnancy. Epinephrine (5 micrograms/ml) increased production of progesterone and also PGs, but only on Day 2 of pseudopregnancy, whereas oxytocin (100 mIU/ml) was found to be without effect on progesterone as well as PG secretion on all days tested. The results of the present study demonstrates the independent ability of the rat CL to synthesize PGG/PGH2-derived prostaglandins, including the putative luteolysin PGF2 alpha. Secondly, we demonstrate that LH and AA-induced increases in PGF2 alpha and PGE2 production during the luteolytic period, may be an autocrine or paracrine mechanism involved in luteolysis.

Animals↗

PubMed1992

Prolactin stimulates the expression of luteinizing hormone/chorionic gonadotropin receptor messenger ribonucleic acid in the rat corpus luteum and rescues early pregnancy from bromocriptine-induced abortion.

Timed pseudopregnancy (psp) and pregnancy were induced in adult female rats by mating with infertile and fertile males, respectively. Corpora lutea (CL) and the residual parts of the ovaries were isolated and analyzed for luteinizing hormone/chorionic gonadotropin (LH/CG) receptor mRNA by Northern blot and solution hybridization analyses. Several LH/CG receptor mRNA transcripts were detected that could code for an intact functional receptor (6.8, 4.4, and 2.6 kb) as well as several smaller truncated transcripts. LH/CG receptor mRNA abundance in CL varied dramatically during both psp and pregnancy, with peak levels seen during the period of maximal progestational activity (Days 5-10 of psp and Days 7-14 of pregnancy). During the period of functional luteolysis, LH/CG receptor mRNA abundance decreased to low levels. The changes in LH/CG receptor expression could be explained by hormonal regulation. Bromocriptine treatment inhibited pituitary prolactin secretion. This treatment had a potent luteolytic effect by decreasing the levels of LH/CG receptor mRNA and plasma progesterone during early pregnancy, resulting in embryonal resorption in pregnant rats. Exogenous prolactin acted as a anti-luteolysin to reverse these effects by restoring LH/CG receptor mRNA abundance either by increasing gene expression or by stabilizing mRNA transcripts from degradation in young CL.

Abortion, Spontaneous↗

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↗

PubMed1991

Regulation of prostaglandin biosynthesis by luteinizing hormone and bradykinin in rat preovulatory follicles in vitro.

Luteinizing hormone (LH) stimulates prostaglandin biosynthesis and steroidogenesis in preovulatory (PO) follicles prior to ovulation. Since the ovulatory process shares many similarities with an inflammatory reaction, mediators of the inflammatory response, such as bradykinin (BK) have been suggested to modulate the effects of LH. In the present study the effect of BK (5 microM) on: 1) prostaglandin biosynthesis (PGE2, PGF2 alpha and 6-keto-PGF1 alpha), 2) the levels of two enzymes in the cyclo-oxygenase pathway, prostaglandin endoperoxide synthase (PGS) and prostacyclin synthase (PCS), and 3) cyclic adenosine 3'5'-monophosphate (cAMP) and progesterone response of PO follicles incubated in vitro were examined. LH (0.1 microgram/ml) stimulated the accumulation of cAMP and progesterone in the medium, while BK had no effect on these parameters. BK exerted a slight stimulatory effect on PGE2, and PGF2 alpha, (p less than or equal to 0.01) but not on 6-keto-PGF1 alpha synthesis, but no changes in PGS or PCS levels could be detected. The effect of LH on prostaglandin biosynthesis was much more pronounced, with an increase of PGE2, PGF2 alpha and 6-keto-PGF1 alpha. LH also induced PGS. The combination of LH and BK did not alter these responses compared to that of LH alone. This study demonstrates that BK stimulates prostaglandin biosynthesis in PO follicles. In contrast to LH, this effect of BK does not seem to involve the adenylate cyclase system, since BK did not stimulate cAMP production. BK did not affect the levels of PGS or PCS, and the stimulatory effect of BK is suggested to involve an increase in the availability of substrate for the cyclo-oxygenase pathway.

Animals↗