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Effects of steroid hormones on nicotinic acetylcholine receptor channel kinetics

100%

Nurowska E., Dworakowska B., Dolowy K.

Postępy Higieny i Medycyny Doświadczalnej

2000

vol. 54

issue 3

363-370

Classically steroid hormones acts through genomic mechanism. In the last period there is more evidence that some steroid hormones exert fast (in order of seconds) effects on membrane receptors. In the presented work we analysed the effects of some steroid hormones on muscle acetylcholine receptor (AChR) channel kinetics. We devided steroid hormone on two groups which exert different effects. The first group including hydrocortisone (HC), corticosterone (COR), dexamethasone decrease the mean open time increasing the number of openings in bursts. The effects do not depend on agonist concentration. Some effects of HC and COR are voltage-dependent. The mechanism of such voltage dependent action caused by steroids hormones that are uncharged molecules, is unknown. Some experiments suggest however that an agonist molecule is involved in the mechanism of steroid action. The second group consists of progesterone, some of its derivatives and deoxycorticosterone. For this group the most evident effect was decrease in the probability of openings without a decrease in the mean open time. The effect depends on agonist concentration, suggesting an involvement of an agonist molecule in the mechanism. For this hormones an involvement of an charged agonist molecule does not however induce a voltage dependency. Most probably two groups of steroids acts on different part of the AChR. The localization of a steroid action site can be crucial for inducing voltage dependency.

Hormonal regulation of oestrogen formation by Leydig cells in vitro: immunocytochemical approach

61%

Gancarczyk M., Tworzydlo W., Szlachta A., Sadowska J., Bilinska B.

Folia Biologica

2003

vol. 51

issue 3-4

181-188

The ability of the testis to convert androgens into oestrogens is related to the presence of a microsomal enzyme, aromatase, in testicular cells. The aim of this study was to show whether the supplementation of culture media with LH or an aromatase inhibitor could affect the process of aromatisation in Leydig cells of the bank vole in vitro. This was investigated by means of immunocytochemistry and radioimmunological assays. In control cultures of Leydig cells, both steroid hormones secretion as well as immunoreactivities for aromatase and oestrogen receptor were weaker than in those treated with LH. On the contrary, the addition of aromatase inhibitor into the culture medium resulted in a decreased intensity of immunocytochemical stainings in comparison with the control. Concomitantly, the androgen level was slightly higher, whereas that of oestrogen significantly lower than in the control cultures. Additionally, to check whether steroid hormones are able to regulate aromatase or oestrogen receptor immunoexpressions, some of the Leydig cell cultures were enriched with testosterone or oestradiol, respectively. Strong immunoreactivities for both aromatase and oestrogen receptor were observed. This suggests that Leydig cells in vitro are able to regulate directly the secretion of oestrogens by active aromatase. Finally, it is concluded that oestrogen formation in bank vole Leydig cells in vitro can be influenced by various factors. It should be stressed, however, that the effect of hormone stimulation or aromatase inhibitor action appeared to be dependent on the length of light cycles that bank voles were exposed prior to the isolation of Leydig cells.

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1 Folia Biologica

1 Postępy Higieny i Medycyny Doświadczalnej

1 2003

1 2000

1 Bilinska B.

1 Dolowy K.

1 Dworakowska B.

1 Gancarczyk M.

1 Nurowska E.

1 Sadowska J.

1 Szlachta A.

1 Tworzydlo W.

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Effects of steroid hormones on nicotinic acetylcholine receptor channel kinetics

Hormonal regulation of oestrogen formation by Leydig cells in vitro: immunocytochemical approach