Endocrine Abstracts

Background: It is known that reactive oxygen species (ROS) production is necessary for the signal transduction mechanism of β-adrenergic receptors.

Aim: Our aim was to investigate whether antioxidant agent (α)-tocopherol-acid-succinate may reduce the effect of β-mimetic action on β(2)-adrenergic receptor regulated tissues.

Methods: Tissue samples were collected from non-pregnant (trachea) and 22-day pregnant (myometrium, cervix) rats. In separated groups of animals, the tracheal and uterine β-adrenoceptor activities were upregulated by 17-β-oestradiol-valerate and progesterone treatment, respectively. Cervical resistance, myometrial and tracheal contractions were investigated in isolated organ bath. The cyclic AMP accumulations in the tissues were measured with competitive cyclic AMP Enzyme Immunoassay (EIA) Kit.

Results: Terbutaline (10⁻⁶ M) increased the cervical resistance both in non-treated and progesterone-treated samples. Tocopherol (10⁻⁷ M) reduced this action in progesterone-treated samples, but had no effect on non-treated cervices. Terbutaline (10⁻¹⁰ to 10⁻⁵ M) decreased the spontaneous myometrial contraction both in non-treated and progesterone-treated tissues. The presence of tocopherol did not alter this action in any cases. Terbutaline (10⁻⁹ to 10⁻⁴ M) reduced the tracheal tones both in non-treated and oestrogen-treated tissues. This effect was reduced by tocopherol in both cases (by 52% in non-treated and 68% in oestrogen-treated tissues). The changes in tissues cAMP levels showed a strong correlation with the isolated organ results.

Conclusions: Tocopherol as a free radical scavenger may interact with the β-mimetic action. This effect is pronounced in trachea, slight in the cervix and non-significant in the myometrium. These results suggest that the ROS may have different significance in the signalling process of β(2)-adrenergic receptors in different tissues.