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T Ranta

Publications and source records attributed to T Ranta.

At least 37 records · Page 2Linked to original sources
PubMed1988

Epidermal growth factor but not insulin-like growth factor-I potentiates adenosine 3',5'-monophosphate-mediated chorionic gonadotropin secretion by cultured human choriocarcinoma cells.

Epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) regulate hormone production in several endocrine cells cultures. We have previously found that 12-O-tetradecanoyl phorbol-13-acetate (TPA), a protein kinase C activator, potentiates the cAMP-mediated secretion of human CB (hCG) in cultured human choriocarcinoma cells. We have now studied whether EGF and IGF-I modify cAMP-mediated hCG secretion in JEG-3 cells, which possess high affinity receptors to these growth factors. EGF, TPA, and cholera toxin (CT), an activator of adenylate cyclase, stimulated the secretion of hCG in a concentration-dependent manner during a 24-h culture period. The maximal effective concentrations of EGF (10 ng/ml), TPA (10 ng/ml), and CT (1.0 ng/ml) exerted 2.3-, 2.4-, and 3.9-fold increase over unstimulated level, respectively. EGF and TPA potentiated the effect of CT on hCG secretion from 3.9- to 7.8-fold and from 3.9- to 14.8-fold, respectively. By contrast, IGF-I was ineffective. During a 24-h culture, EGF and TPA potentiated the effect of CT on cAMP accumulation 1.4-fold and 1.3-fold over the production of CT-treated cells. Time-course studies indicated that these effects on cAMP and hCG were detectable at 3 h and 6 h, and they continued to increase up to 48 h and 72 h, respectively. When added alone, EGF and TPA increased cAMP production y 2.0-fold and 2.5-fold over controls at 24 h. Again, IGF-I was ineffective. Moreover, EGF and TPA potentiated the effect of 8-bromo-cAMP (on hCG production to a similar extent than they did to CT-stimulated hCG production. The binding of [125I]iodo-EGF to the cells was not altered by a 48-h CT-treatment whereas the binding of [125I]iodo-IGF-I was increased by 2.1-fold above untreated cells. Our data show that both EGF and TPA potentiated the effect of CT on hCG secretion in JEG-3 cells, whereas IGF-I had no effect. Although EGF and TPA facilitated CT-stimulated cAMP accumulation, their site of action on cAMP-mediated hCG production is distinct from the adenylate cyclase or EGF-receptor level since EGF and TPA potentiated the hCG secretion stimulated by 8-bromo-cAMP and an increase in cAMP production did not alter the binding properties of EGF-receptor.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Phorbol ester stimulates human granulosa-luteal cell cyclic adenosine 3', 5'-monophosphate and progesterone production.

Human granulosa-luteal cell production of cyclic adenosine 3', 5'-monophosphate (cAMP) and progesterone (P) were studied in response to 12-O-tetradecanoyl-phorbol-13-acetate (TPA). TPA specifically increased cAMP synthesis in a dose-dependent manner. A 7-fold increase occurred at a TPA concentration of 1 ng/ml. Time-course studies indicated that the increase in accumulation of cAMP into culture media became detectable at 4 h and continued up to 72 h. TPA also enhanced P synthesis, but the increase was statistically significant only at 72 h. Indomethacin prevented TPA-stimulated cAMP and P production. The results suggest that TPA stimulates granulosa-luteal cell cAMP and P production, and that the action of TPA is mediated by the increase in prostaglandin synthesis.

Corpus Luteum↗
PubMed1987

12-O-tetradecanoyl phorbol-13-acetate potentiates adenosine 3',5'-monophosphate-mediated chorionic gonadotropin secretion by cultured human choriocarcinoma cells.

The activation of protein kinase C and adenylate cyclase in the regulation of human CG (hCG) synthesis by cultured BeWo choriocarcinoma cells was studied. Both cholera toxin (CT), which activates adenylate cyclase, and 12-O-tetradecanoyl phorbol-13-acetate (TPA), a protein kinase C activator, stimulated the secretion of hCG in a dose-dependent manner. During a 72-h culture, stimulation with the maximal effective concentration of CT (1.0 ng/ml) exerted a more pronounced increase (16-fold) in hCG synthesis than TPA (10 ng/ml) (2.8-fold), whereas the inactive phorbol ester 4 alpha-phorbol 12,13-didecanoate (100 ng/ml) was ineffective. When added together, TPA potentiated the effect of CT on hCG secretion (from 16- to 27-fold) and cAMP accumulation (from 36- to 54-fold) in the medium. TPA (1.0 ng/ml) also caused a 2.0-fold increase in basal cAMP production after 72 h. Time-course studies indicated that the effect of TPA on CT-induced cAMP and hCG productions became significant at 45 min and 6 h, respectively, from the beginning of stimulation. Proliferation of cells was not responsible for the responses, since the treatments only slightly increased the total protein content and did not alter the rate of incorporation of C3H3-methylated thymidine of the cells. Our results demonstrate that TPA potentiates CT-induced cAMP and hCG production in cultured human choriocarcinoma cells.

Adenylyl Cyclases↗
PubMed1987

Serum levels of human chorionic gonadotropin in nonpregnant women and men are modulated by gonadotropin-releasing hormone and sex steroids.

Serum hCG levels were measured in apparently healthy nonpregnant women and men using a highly sensitive and specific time-resolved immunofluorometric assay. The sensitivity of the assay was 0.03 IU/L. The levels were low in women of fertile age (median, 0.05 IU/L) and in men less than 60 yr of age (median, 0.04 IU/L). In women the median level increased to 1.1 IU/L after the menopause (range, 0.17-4.8 IU/L), and a similar but smaller increase occurred in men after 60 yr of age (median, 0.20 IU/L; range, less than 0.03-2.3). Stimulation with GnRH caused a 2- to 3-fold increase in the hCG level in both men and women. Chronic treatment of postmenopausal women with a combination of estrogen and progestagen lowered their serum hCG levels to about 50% of the pretreatment values. The hCG in serum could be separated from LH by gel chromatography, and the hCG immunoreactivity measured by direct assay of serum corresponded to the immunoreactivity eluted in the hCG fractions after gel chromatography. Thus, the results were not due to cross-reaction with LH. We conclude that serum of nonpregnant women and men contains hCG-like material, whose production is modulated by GnRH and sex steroids.

Adult↗
PubMed1987

Follicle-stimulating hormone receptors appear earlier in the primate fetal testis than in the ovary.

Receptors for FSH as well as FSH-stimulated cAMP production were measured in gonadal tissue of human fetuses of 8-16 weeks gestation and of rhesus monkey fetuses in the last third of gestation. A single population of high affinity receptors (Ka, 1.5-4 X 10(9) M-1) for human FSH was detected in testicular tissue of both species. Specific FSH binding was absent in the human ovaries but present in the two monkey fetal ovaries studied. FSH (1 microgram/mL) did not stimulate cAMP production in slices of any of the gonads studied (human fetal testes and monkey fetal testes and ovaries) or in cultured human granulosaluteal cells used in a control experiment, but FSH increased cAMP 10-fold in immature (10-day-old) rat testes. We conclude that the primate fetal testis, both during the first half and at the end of gestation, may be responsive to FSH stimulation, although this response does not involve the acute elevation of cAMP. In contrast, the absence of FSH receptors in early and midterm human fetal ovaries and the presence of such binding in this tissue in the late gestation monkey indicate that the ovary becomes responsive to FSH stimulation during later stages of fetal development.

Aged↗
PubMed1987

Receptor binding properties and biologic action of deglycosylated human chorionic gonadotropin in human ovary and testis.

The receptor binding properties and biologic actions of chemically deglycosylated-asialo human choriogonadotropin (AHF-hCG) were studied in human ovary and testis. In corpus luteum and testis homogenates, the relative binding affinity of AHF-hCG was two- to fourfold higher in the ovary and five- to tenfold higher in the testis than that of native hCG. When assayed for luteinizing hormone (LH)-like activity in granulosa-luteal cells from in vitro fertilization patients and in testicular minces from patients undergoing orchiectomy for prostatic cancer, AHF-hCG did not stimulate cyclic adenosine monophosphate production. When added with hCG to granulosa-luteal cells or to testicular minces, AHF-hCG inhibited hCG-stimulated cyclic adenosine monophosphate production. These results indicate that the enhanced affinity to LH receptor caused by removal of the sugar moieties from hCG is associated with total inability to activate granulosa-luteal and Leydig cell adenylate cyclase, and that AHF-hCG is, in the human gonad, an hCG antagonist.

Adenosine Monophosphate↗
PubMed1987

Serum prolactin levels after buspirone in man.

The acute effects of buspirone, an anxiolytic with mixed dopamine (DA) agonist-antagonist properties (achieved by blocking pre- and postsynaptic receptors) on serum prolactin (PRL) were studied in cross-over and double-blind trials in ten healthy young males. Sulpiride (200 mg) was used as a control drug; it raised PRL by almost 800%. Buspirone (25, 50 and 100 mg) raised serum PRL dose-dependently; the greatest increases (30, 70, and 320% from baseline, respectively) were seen 1 h after each dose. The results suggest that buspirone blocks postsynaptic DA receptors only at doses higher than those needed for anxiolysis.

Adult↗
PubMed1986

In vitro recovery of human chorionic gonadotropin-stimulated cyclic adenosine 3',5'-monophosphate production in desensitized human granulosa-luteal cells.

Human granulosa-luteal cell production of cyclic adenosine 3',5'-monophosphate (cAMP) and progesterone (P) were studied in response to purified human chorionic gonadotropin (hCG) in cultured cells from hyperstimulated follicles of in vitro fertilized patients. The hCG injection given to the patients 36 hours before laparoscopy caused partial desensitization of adenylate cyclase of these cells to gonadotropins. Preincubation of the cells in hormone free medium for 2 to 3 days significantly increased their cAMP responsiveness to hCG. P production was stimulated initially by hCG and showed no desensitization. In the cells preincubated for 72 hours without hCG, a subsequent stimulus of 50 ng/ml of hCG elicited maximal cAMP response, whereas 1 ng/ml of hCG was sufficient to bring about maximal P secretion. Time-course studies indicated that maximal cAMP response to hCG was obtained in 1 to 3 hours. Both basal and hCG-stimulated P accumulation continued to rise for up to 24 hours. Preincubation of granulosa-luteal cells from hyperstimulated follicles improves the cells' cAMP responsiveness to hCG, whereas P response remains unaltered.

Chorionic Gonadotropin↗
PubMed1986

Activation of protein kinase-C stimulates human granulosa-luteal cell prostacyclin production.

To study the production of prostacyclin (PGI2) by human granulosa-luteal cells in vitro, individual follicles from clomiphene/human menopausal gonadotropin-stimulated cycles of patients undergoing in vitro fertilization were aspirated 36 h after the administration of hCG. Granulosa cells were isolated and cultured for 48 h to regain responsiveness to hCG. The cells were then recultured for 3 days in the presence of a protein kinase-C activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), hCG, cholera toxin, and indomethacin. The media were assayed for 6-keto-prostaglandin F1 alpha (PGF1 alpha), a stable hydration product of PGI2. TPA increased granulosa cell PGI2 production 20-fold. The increase in PG synthesis was detectable at 12 h, was maximal at 72 h, and was prevented by indomethacin. The increase in PG production was specific to TPA and did not occur when an inactive phorbol ester, 4 alpha-phorbol-12,13-didecanoate, was used. hCG and cholera toxin stimulated granulosa cell cAMP production, but not PGI2 synthesis. Thus, human granulosa cells produce PGI2 by protein kinase-C-mediated mechanisms.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Gonadotropin-releasing hormone as a modulator of ovarian function.

GnRH and its agonist analogs exert direct inhibitory and stimulatory effects on the ovaries of animals from several species. In the immature follicle, GnRH inhibits the actions of FSH on an integrated array of biochemical responses that lead to follicular development and corpus luteum formation. GnRH also suppresses gonadotropin action in mature follicles, and stimulates certain ovarian processes such as steroidogenesis and oocyte maturation. The inhibitory and stimulatory effects of GnRH are mediated through the binding of the peptide to high-affinity receptors in granulosa and thecal cells. Recent studies have shown that GnRH action in the ovary is dependent upon calcium mobilization and probably operates through stimulation of phospholipid turnover and activation of protein kinase C.

Animals↗
PubMed1985

Placental protein 10 (PP10) in normal pregnancy and cholestasis of pregnancy.

The circulating concentrations of placental protein 10 (PP10) were measured by radioimmunoassay in 288 women with normal pregnancy and ten women (55 samples) with cholestasis of pregnancy. Serum PP10 levels were not affected by changes in incubation and storage temperature, and no diurnal variation was observed. The highest PP10 levels (36-85 micrograms/l) in normal pregnancy were found at 34 weeks. The postpartum decline of serum PP10 concentration corresponded to an average half-life of 18 h. In cholestasis of pregnancy at 32-39 weeks, the serum PP10 levels were found to be lower than normal. Negative correlation was observed between aminotransferase and PP10 levels in serum and between the bile acid levels and the PP10 concentration. These results suggest that the severity of maternal liver disorder is reflected in the circulating PP10 concentration.

Bile Acids and Salts↗
PubMed1985

Distribution of placental protein 14 in tissues and body fluids during pregnancy.

Placental protein 14 (PP14) levels were measured in serum samples from non-pregnant and pregnant women, amniotic fluid, cord blood, and extracts of placenta, decidua and fetal membranes. The levels were low (15-40 micrograms/l) in serum of non-pregnant women. In four pregnancies following in-vitro fertilization, the serum PP14 levels started to rise 2-12 days after embryo replacement. In normal pregnancy, the highest serum PP14 concentrations (up to 2200 micrograms/l) were detected between 6 and 12 weeks. After 16 weeks the level decreased and plateaued at 24 weeks to around 200 micrograms/l. In amniotic fluid, the highest PP14 levels (232 mg/l) were found between 12 and 20 weeks, being considerably higher than those in maternal serum throughout pregnancy. In cord blood, the levels were low (15-22 micrograms/l) or undetectable. In early pregnancy decidua, the PP14 content was higher (41-160 mg/g total protein) than in late pregnancy decidua (60-2700 micrograms/g total protein). In amnion and chorion laeve, the PP14 concentration varied from 50 to 750 and 50 to 1000 micrograms/g protein, respectively. Early pregnancy placenta contained 0.25-15 mg/g and late pregnancy placenta 3-430 micrograms/g protein of PP14. These results show that the levels of PP14 in pregnancy serum have a similar profile to hCG, but in contrast to other placental proteins, the amniotic fluid PP14 levels are remarkably high. This may be explained by suggesting that decidua is a source of PP14.

Amniotic Fluid↗
PubMed1985

Enhanced follicle-stimulating hormone activity of deglycosylated human chorionic gonadotropin in ovarian granulosa cells.

The receptor binding properties and biological actions of chemically deglycosylated asialo human CG (AHF-hCG) were studied in ovarian granulosa cells from diethylstilbestrol (DES)-treated immature rats. In ovarian homogenates from DES- and FSH-treated rats, the relative binding affinity of AHF-hCG was 2-fold higher than that of native hCG and 14-fold higher than that of ovine LH. When assayed for LH-like activity in granulosa cells from DES plus FSH-treated animals, the deglycosylated hormone behaved as a partial agonist in terms of cAMP formation, but fully stimulated progesterone production to the same extent as that elicited by LH. When added with LH to FSH-treated cells, AHF-hCG inhibited LH-stimulated cAMP formation by 70% but did not alter the elevated level of progesterone production. These findings are consistent with the presence of excess or spare LH receptors in the maturing granulosa cell. When added to freshly prepared granulosa cells which have minimal LH receptors, AHF-hCG decreased FSH-stimulated cAMP production by 20% and reduced progesterone production by 50% and increased cGMP formation by 100% during 48 h of culture. The ability of AHF-hCG to decrease the progesterone response to FSH suggests that no spare FSH receptors are present during granulosa cell differentiation. In contrast, native hCG did not alter FSH-induced cAMP or progesterone production but reduced the cGMP responses to FSH and choleragen. Whereas native hCG displayed negligible binding potency when compared with that of ovine FSH in competition with [125I]iodo-human FSH for ovarian receptors, AHF-hCG bound to FSH receptors with about 5% of the binding affinity of ovine FSH. In choleragen-treated granulosa cells, the increases in cAMP and progesterone synthesis were enhanced by addition of both hCG and AHF-hCG, and cGMP production was increased by AHF-hCG but slightly decreased by hCG. These results indicate that the enhanced LH receptor affinity caused by removal of the sugar moieties from hCG is accompanied by a relatively greater increase in FSH receptor affinity, and that deglycosylated hCG acts as a partial agonist with the ability to modify granulosa cell responses to both LH and FSH.

Animals↗
PubMed1985

Synthesis of placental protein 12 by human decidua.

The synthesis and secretion of placental protein 12 (PP12) were studied in tissue culture using explants of decidua, amnion, chorion, and placenta from seven full term pregnancies. The total amounts of PP12 in media and tissues were measured by RIA, and new protein synthesis and secretion by decidual explants were demonstrated by the incorporation of [35S]methionine into PP12 after 20 h of incubation with 12.5 microCi/ml [35S]methionine. Cycloheximide was used to study the effect of a protein synthesis inhibitor on the secretion of PP12 by decidua. Significantly more PP12 (P less than 0.001) was released into the medium from decidual explants than from chorion and amnion explants throughout the experimental period of 24 h. When incubated under identical conditions, placental explants released no detectable PP12. In decidual tissues and their culture media, the total amount of PP12 was 127.4% higher after incubation than before incubation (P less than 0.001). No increase was found when chorion and amnion were cultured. The addition of cycloheximide into cultures decreased the total amount of PP12 in the decidua and in its culture medium by more than 50%, indicating that one part of PP12 in decidua was performed and another part was newly synthesized. Decidual explants incorporated [35S]methionine into immunoprecipitable PP12 indicating new PP12 synthesis. In gel filtration, 77% of decidual [35S] PP12 eluted in the same position as purified PP12. In sodium dodecyl sulfate polyacrylamide gel electrophoresis, the migration mobility of [35S]PP12 was identical with that of purified PP12. Our results clearly demonstrate that PP12 is a decidual rather than a placental protein.

Culture Media↗
PubMed1984

Hormonal regulation of cyclic AMP-dependent protein kinase in cultured ovarian granulosa cells. Effects of follicle-stimulating hormone and gonadotropin-releasing hormone.

The hormonal regulation of cAMP-dependent protein kinase was examined in granulosa cells from diethylstilbestrol-implanted immature rats. Follicle-stimulating hormone (FSH) increased the number of available cAMP-binding sites in a dose- and time-dependent manner, with a maximum 4-6-fold increase at 50-100 ng/ml between 6 and 48 h of culture after a transient decrease in available sites during the first 6 h. The potent gonadotropin-releasing hormone (GnRH) agonist [D - Ala6]des - Gly10 - GnRH - N - ethylamide (GnRHa) reduced the FSH-induced increase in cAMP-binding sites by approximately 50% at 24 and 48 h of culture. Photoaffinity labeling with 8-azido-[32P] cAMP revealed the existence of one major cAMP-binding protein (Mr = 55,000 +/- 400) which appeared to be the regulatory (R) subunit of type II cAMP-dependent protein kinase. While FSH induced a 5-10-fold increase in the labeling of R II both in vivo and in vitro, GnRHa reduced the amount of R II induced by FSH in granulosa cells cultured for 48 h. The large increase in R II subunit was not accompanied by a corresponding increase in protein kinase activity, which was only enhanced by 50% after 48 h of culture with FSH. Fractionation of granulosa cell cytosol from FSH-treated ovaries on DEAE-cellulose showed a single peak of cAMP-dependent phosphokinase activity with the elution properties of a type II protein kinase. However, the peak of cAMP binding activity (eluted at 0.20 M KCl) was not coincident with the protein kinase activity. FSH transiently stimulated cAMP-dependent protein kinase activity during the first 10-30 min of culture. GnRHa impaired the FSH-induced early increase in protein kinase activity, causing a delay in activation until 60 min. These findings suggest that a large dose- and time-dependent increase in the content of cAMP-binding sites may be a major factor in cAMP-mediated differentiation of granulosa cells. The inhibitory effect of GnRHa on both FSH-induced protein kinase activation during the first minutes of culture and on FSH-induced R II synthesis during the subsequent 48 h of culture could be crucial events in the prevention of granulosa cell maturation by GnRH agonists.

Animals↗