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Increases in ornithine decarboxylase activity in the positive inotropism induced by androgens in isolated left atrium of the rat.

Abstract：

:It is well established that the intracellular receptors of androgens act as transcription factors upon their activation by androgen binding. However, a growing number of studies have associated androgens with rapid biological responses independent of their classical action mechanism. In this sense, 5alpha- and 5beta-dihydrotestosterone elicited a rapid positive inotropism in the isolated left atrium of the rat via cAMP-dependent mechanisms that may involve genomic effects. In addition, polyamines are mediators of several biological actions including those acute and long-term effects induced by androgens in the heart. The present study analyzed the role of polyamine synthesis in the cardiotonic effect of androgens in the left atrium of male Wistar rats, electrically stimulated (0.5 Hz, 5 ms and supramaximal voltage) and placed in an organ bath in 10 ml of Tyrode's solution. Incubation in the organ bath with an inhibitor of ornithine decarboxylase activity, alpha-difluoromethylornithine 10 mM, significantly decreased the positive inotropism induced by 5alpha- and 5beta-dihydrotestosterone (0.1-100 microM). This suggests that ornithine decarboxylase seems to be involved in androgen-induced positive inotropism. Furthermore, 6-min exposure to 5alpha- or 5beta-dihydrotestosterone significantly increased the activity of ornithine decarboxylase from 61.81+/-7.53 (control) to 93.28+/-9.45 and 80.28+/-12 pmol/h/mg of protein, respectively. Northern blot analysis showed that 5alpha- and 5beta-dihydrotestosterone did not modify the level of expression of the ornithine decarboxylase gene. Therefore, our results suggest that polyamine synthesis might be involved in the positive inotropism elicited by androgens through the stimulation of ornithine decarboxylase activity without changes in the expression of the ornithine decarboxylase gene.

journal_name

Eur J Pharmacol

journal_title

European journal of pharmacology

authors

Bordallo C,Rubín JM,Varona AB,Cantabrana B,Hidalgo A,Sánchez M

doi

10.1016/s0014-2999(01)01039-1

keywords:

subject

Has Abstract

pub_date

2001-06-22 00:00:00

pages

101-7

issue

1-3

eissn

0014-2999

issn

1879-0712

pii

S0014299901010391

journal_volume

422

pub_type

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Increases in ornithine decarboxylase activity in the positive inotropism induced by androgens in isolated left atrium of the rat.