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Biomedical subjects

A H Ree

Publications and source records attributed to A H Ree.

24 records · Page 2Linked to original sources
PubMed1991

Cellular localization of mRNAs for retinoic acid receptor-alpha, cellular retinol-binding protein, and cellular retinoic acid-binding protein in rat testis: evidence for germ cell-specific mRNAs.

In the present study we have examined the cellular localization and developmental changes of mRNAs for retinoid-binding proteins in rat testis. We demonstrate that mRNA (0.7 kb) for cellular retinol-binding protein (CRBP) is expressed only in Sertoli cells and peritubular cells. The mRNA for CRBP could not be detected in other testicular cells. In contrast, mRNA for cellular retinoic acid-binding protein (CRABP) was detected primarily in germ cells and to a small extent in tumor Leydig cells. The mRNA for CRABP in germ cells revealed distinct size heterogeneity and three distinct mRNA species were observed (1.0, 1.8, and 1.9 kb), in contrast to previous data for somatic cells where only the 1.0-kb mRNA has been reported. Messenger RNAs for retinoic acid receptor-alpha (RAR alpha) were detected in both somatic and haploid germ cells. The highest level of RAR alpha was seen in Sertoli cells, round spermatids, and tumor Leydig cells. Lower, but distinct, levels were observed in peritubular cells. Furthermore, we observed germ cell-specific species of RAR alpha mRNA (4 kb and approximately 7 kb). The smallest mRNA for RAR alpha (2.7 kb) in somatic cells was absent in germ cells. The levels of mRNAs for the various retinoid-binding proteins in whole testis obtained from rats of various ages confirmed this cellular localization. The mRNAs for CRBP, the small molecular size (2.7 kb) mRNA for RAR alpha (localized to somatic cells), and the 1-kb mRNA for CRABP showed an age-dependent decrease.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Down-regulation of messenger ribonucleic acid and protein levels for estrogen receptors by phorbol ester and calcium in MCF-7 cells.

Treatment of MCF-7 cells, a human mammary carcinoma cell line, with phorbol ester [12-O-tetradecanoylphorbol-13-acetate (TPA)] or calcium ionophore (A23187) was associated with striking effects on levels of estrogen receptor (ER) mRNA, specific binding of 17 beta-[3H]estradiol [( 3H]E2), and immunoreactive ER. TPA (10(-7) M) caused a time-dependent reduction of ER mRNA which was below the level of detection after 9 h. Similar effects of TPA appeared at levels of specific binding of [3H]E2 as well as immunoreactive ER. In contrast, TPA induced an increase in mRNA for beta-actin. Incubation of MCF-7 cells with increasing concentrations of TPA (10(-11)-10(-7) M) was associated with biphasic effects on ER mRNA and proteins. Levels of immunoreactive progesterone receptors (PR) were induced by E2 (10(-9) M) in a time-dependent manner. In the presence of TPA (10(-7) M), where ER levels were suppressed, no induction of PR was observed. Removal of TPA (10(-7) M) after 10 h (ER mRNA) or 22 h (ER proteins) of treatment was associated with a continued suppression of both mRNA and protein levels during the entire incubation period (48 h). Treatment with A23187 (2 x 10(-7) M) also caused a time-dependent down-regulation of levels of ER mRNA and proteins. These effects occurred somewhat more slowly than those of TPA. Levels of beta-actin mRNA were not changed by this treatment. These results indicate that changes in estrogen sensitivity are mediated by calcium-dependent protein kinases in human mammary carcinoma MCF-7 cells.

Breast Neoplasms↗
PubMed1990

Biphasic regulation of the messenger ribonucleic acid coding for the estrogen receptor by cyclic adenosine 3':5'-monophosphate in tumor Leydig cells.

In this report we show that the mRNA level for the estrogen receptor (ER) is regulated by 8-bromo cyclic AMP (8-Br-cAMP) and human chorionic gonadotropin in a mouse tumor Leydig cell line (MA-10 cells). When the MA-10 cells were cultured in the presence of the cAMP analogue for varying time periods, a transient increase in the level of ER mRNA was observed. Short time incubation (0-2 h) with 8-Br-cAMP enhanced the expression of ER mRNA (2-fold), whereas longer times of incubation (6 h) had the opposite effect (the level of ER mRNA was reduced by 60-70%). The inhibitory effect of 8-Br-cAMP on ER mRNA was not counteracted by aminoglutethimide, an inhibitor of steroidogenic enzymes, indicating that this effect is not mediated via steroids (progesterone). Treatment of 8-Br-cAMP for 6 h caused a concentration-dependent inhibition of ER mRNA with a half-maximal effect of approximately 150 microM. Increasing concentrations of human chorionic gonadotropin for 6 h was also associated with a biphasic effect on the ER mRNA level. Low concentrations (0.20-0.40 ng/ml) increased ER mRNA in the MA-10 cells whereas the highest concentration (20 ng/ml) caused a suppression of this mRNA. In contrast to the biphasic effects observed for the ER mRNA, the level of the regulatory subunit type II beta of the cAMP-dependent protein kinase (protein kinase A) was enhanced in a concentration-dependent manner by human chorionic gonadotropin. Furthermore, 8-Br-cAMP stimulated the mRNA for regulatory subunit type II beta (10- to 20-fold) by all concentrations examined (50-1000 microM). The observations reported here indicate that the expression of ER mRNA is regulated both by endogenously formed and exogenously added cAMP and that there may exist regulatory loops between the steroid and the cAMP/protein kinase A systems.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

Glucocorticoid receptors and glucocorticoid effects in rat Sertoli cells.

In this report we demonstrate glucocorticoid receptors in seminiferous tubules of the rat testis, and that these receptors are localized in Sertoli cells and peritubular cells. The receptors had high affinity for [3H]dexamethasone (Kd = 0.5 - 1 x 10(-9) M), and similar Kd values were calculated from equilibrium analysis and from rate studies (k1 = 1.5 x 10(6) M-1 min-1 and k-1 = 1.4 x 10(-3) min-1, O C). Binding specificity was typical for glucocorticoid receptors (affinity: dexamethasone greater than corticosterone greater than cortisol approximately R5020 approximately progesterone greater than aldosterone = R1881 greater than 17 beta-estradiol approximately cortisone approximately testosterone greater than 5 alpha-dihydrotestosterone). The concentration of glucocorticoid receptors in rat seminiferous tubules revealed an age-dependent decrease, coinciding with the increase in the number of germ cells. Glucocorticoid receptor levels were higher in Sertoli cells from immature rats than in cells from adult rats. Cultured peritubular cells from immature rats contained levels of glucocorticoid receptors similar to cultured Sertoli cells from rats of the same age. With a nick-translated human glucocorticoid receptor complementary DNA probe, a messenger RNA (mRNA) species of approximately 7 kilobase was clearly detected in both Sertoli cells and peritubular cells. In peritubular cells, a smaller mRNA species (5 kilobase) was also clearly detectable. In mRNA from whole testis tissue, a similar developmental pattern as for dexamethasone binding was found. Dexamethasone caused a concentration-dependent stimulation of mRNA levels for androgen binding protein and for the cAMP-dependent protein kinase regulatory subunit type II beta in cultured immature rat Sertoli cells. On the other hand, mRNA levels for glucocorticoid receptor decreased, whereas mRNA levels for beta-actin remained constant. This report documents for the first time the presence of glucocorticoid receptors and glucocorticoid effects in rat Sertoli cells, and is also the first demonstration of glucocorticoid receptors in peritubular cells of the rat testis.

Aging↗
PubMed1989

Autologous down-regulation of messenger ribonucleic acid and protein levels for estrogen receptors in MCF-7 cells: an inverse correlation to progesterone receptor levels.

In the present study we have examined the effects of estradiol on mRNA levels for estrogen (ER) and progesterone receptors (PR) in the estrogen-dependent mammary carcinoma MCF-7 cell line. The changes in ER immunoactivity and specific binding of [3H]R5020 were also assessed. Estradiol (10(-7) M) caused a transient and time-dependent reduction of the level of mRNA for ER, with a maximal effect (30-40% of control; n = 3) after 72 h. This was associated with a similar decrease in ER immunoactivity. Further treatment (96 and 120 h) revealed a return of ER mRNA to control values, whereas the ER immunoactivity remained depressed. The effect on the mRNA level for PR gave almost the inverse curve. Initially (24-72 h), we observed a pronounced increase in this mRNA, with a maximal effect (6-7 times the control value; n = 3) after 72 h. Treatment beyond 72 h was associated with a gradual return of mRNA for PR toward the control level. The variation in specific binding of [3H]R5020 revealed similar changes, except that changes in specific receptor binding were delayed 24 h compared to the levels of mRNA. Incubation with low concentrations (10(-11) and 10(-10) M) of estradiol for 72 h was associated with slightly elevated levels of mRNA for ER, whereas higher concentrations gave a dose-dependent decrease. The mRNA for PR was biphasically stimulated, with a maximal effect at 10(-10)-10(-8) M, where a 10- to 13-fold stimulation was observed. The highest concentration (10(-7) M) gave a lower response. Assessment of concentration-induced variations in protein receptor levels of ER and PR reflected the effects of estradiol on their mRNAs. Low concentrations of estradiol slightly enhanced the ER level, whereas high concentrations clearly reduced ER immunoactivity. The PR level was stimulated by all concentrations used, and 10(-8) M estradiol raised the PR level more than 11-fold. Our results indicate autologous regulation of estrogen receptor gene transcripts and proteins and a clear induction of PR mRNA and receptor proteins by estradiol.

Adenocarcinoma↗