Testosterone stimulation of a rapidly labeled, low-molecular-weight RNA fraction in human hepatic erythroid cells in culture.

Abstract

The addition of erythropoietin to cell cultures of erythroid cells of human fetal liver resulted in an increased incorporation of thymidine, adenine, and uridine into trichloroacetic acid-insoluble cell fractions and in an increased uptake of adenine and uridine into the cell. Although the effects of testosterone and erythropoietin on heme synthesis in these cells are known to be very similar, there was no effect of testosterone on the total incorporation of radioactive precursors into DNA or RNA. The RNA synthesized after short pulses of radioactive uridine, when analyzed on sucrose gradients containing 1% sodium dodecyl sulfate, consisted of a homogeneous peak sedimenting at 10 i 2 S, which is quite different from the heterogeneous, high-molecular-weight RNA synthesized under identical conditions in primary cultures of human fetal lung, kidney, or liver parenchymal cells. Addition of testosterone to liver erythroid cells in cultures for 5 hr followed by a 1-hr uridine pulse resulted in a 3-fold increase of RNA species with an average sedimentation coefficient of 14 A4 3 S. The similarity with the sedimentation coefficient of the globin mRNA described in other systems and the high degree of specialization of the erythroid cells suggest that this RNA may be a stable intermediate involved in the synthesis of hemoglobin.One of the earliest actions of erythropoietin on its target cells is the stimulation of RNA synthesis (1-6). We have found that primary cultures of erythroid cells from human fetal liver exhibited an enhanced synthesis of heme after addition of erythropoietin or testosterone and that the heme fraction associated with hemoglobin showed the highest stimulation (7).At the present time it cannot be said with certainty if testosterone itself is active in hematopoietic cells or whether it exerts its effects via a metabolite(s) with the 5,8-configuration. Several observations support a direct role of testosterone. Erythropoietic mouse spleen and rat bone marrow cells contain testosterone receptors, and there is no metabolism of the hormone in mouse spleen (8,9). The effects of testosterone on colony formation in hematopoietic cells of mice are seen within a few minutes after hormone administration (10) when extensive metabolism of the hormone is not to be expected. In this system testosterone and 5(3-metabolites are equally active in colony formation, whereas in human fetal erythroid cells testosterone seems to be the most active of a large number of steroids tested to date (ref. 7, and our own unpublished results). There are two pieces of evidence that suggest a role of metabolites with the 5(3-configuration. One is the high degree of specificity of the action of 5,B-reduced steroids in human bone marrow cells, where both heme and globin synthesis are stimulated (11). Another supporting piece of evidence is the rapid metabolism of testosterone to androstenedione and 523 etiocholanolone in human fetal liver cells (7 centrations were 50 nM testosterone and 0.5 U/ml of erythropoietin. The methods us...

Influence of Maternal Diabetes in Rats on Hemoglobin Synthesis and Uridine Uptake by Fetal Liver Cells

“…The second group of chains (C, D, and E) are beta chains typical of adult hemoglobins, and are synthesized mainly in cells from 16-day-old fetuses. Therefore, it is still possible that, at an earlier gestational period (days [12][13][14][15][16][17], the binding to glucocorticoids in fetal liver cell cultures of control and diabetic rats is different. 13 One of the advantages of the HPLC system used is that the embryonic chains are well separated from the adult beta chains.…”

Μηχανισμοι Που Ελεγχουν Την Αρρενωποτητα (Πειραματικη Μελετη Σε Δυο Στελεχη Ποντικων)

“…Η διαφορά οφείλεται στο ότι η Τεστοστερόνη διεγείρει την ερυθροποίηση από τη μια αυξάνοντας την έκκριση της ερυθροποιητίνης από τους νεφρούς 9 και | από την άλλη, δρώντας κατευθείαν στο μυελό των οστών μέσω των 5β-. ανηγμένων μεταβολιτών της -όπως περιγράφεται παρακάτω 44 . Τα αρσενικά ζώα έχουν περισσότερο ανεπτυγμένο σκελετικό μυϊκό σύστημα, απ' ότι τα θηλυκά, και η διαφορά αυτή οφείλεται σε μεγάλο βαθμό στα ανδρογόνα.…”