title: Interaction of gonadal steroids and the glucocorticoid corticosterone in the regulation of the L-type Ca(2+) current in rat left ventricular cardiomyocytes.
abstract: OBJECTIVE
  Gonadal steroids as well as glucocorticoids have been shown to regulate the cardiac L-type Ca(2+) current (I(CaL) ). Herein, we compare the effects of the gonadal steroids testosterone and 17β-estradiol with the glucocorticoid corticosterone on I(CaL) , and investigate the interaction between the gonadal steroids and corticosterone.
  
  
  METHODS
  Myocytes were isolated from the left ventricular free wall of female and male Wistar rats and investigated using the ruptured-patch whole-cell patch-clamp technique.
  
  
  RESULTS
  In myocytes isolated from female rats, 24 h incubation with 100 nm testosterone led to a 33% increase in I(CaL) compared with control (-8.8 ± 0.5 pA pF(-1) , n = 25 vs. -6.6 ± 0.4 pA pF(-1) , n = 26, P < 0.01, V(Pip) = 0 mV). Incubation with 1 μm corticosterone resulted in a 79% increase in I(CaL) (-11.8 ± 0.7 pA pF(-1) , n = 29, P < 0.001). However, the combination of testosterone and corticosterone did not have any additional effect compared with corticosterone alone (-11.7 ± 0.6 pA pF(-1) , n = 25, ns). In cardiomyocytes from male rats, I(CaL) was not affected by testosterone, whereas the effect of corticosterone was preserved (P < 0.05). 24 h incubation with 17β-estradiol increased I(CaL) by 32% from -7.6 ± 0.5 pA pF(-1) (n = 15) to 10.0 ± 0.9 pA pF(-1) (n = 15, P < 0.05). 17β-estradiol did not exert an additional effect upon co-incubation with corticosterone and did not have an effect on I(CaL) in cardiomyocytes from female rats. Higher concentrations of the gonadal steroids did not result in increased effects.
  
  
  CONCLUSIONS
  When compared with corticosterone, the in vitro effects of the gonadal steroids are small. However, under conditions in which I(CaL) is not fully activated by glucocorticoids, gonadal steroids may significantly contribute to I(CaL) regulation.
authors.affiliation: Institut für Zelluläre und Molekulare Physiologie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany. michael.wagner@physiologie2.med.uni-erlangen.de
authors.forename: M
authors.initials: M
authors.lastname: Wagner
authors.forename: A
authors.initials: A
authors.lastname: Moritz
authors.forename: T
authors.initials: T
authors.lastname: Volk
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000502:physiology*; D002478:Cells, Cultured; D003345:Corticosterone / Q000502:physiology*; D004958:Estradiol / Q000502:physiology*; D005260:Female; D006352:Heart Ventricles; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D032383:Myocytes, Cardiac / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D013739:Testosterone / Q000502:physiology*
chemical_list: D020746:Calcium Channels, L-Type; D013739:Testosterone; D004958:Estradiol; D003345:Corticosterone