Rapid stimulatory effect of thyroxine on plasma membrane transport systems: Calcium uptake and neutral amino acid accumulation in immature rat testis

• Published in: The international journal of biochemistry & cell biology Vol. 42; no. 6; pp. 1046 - 1051
• Main Authors: Menegaz, Danusa, Royer, Carine, Rosso, Angela, Souza, Ariane Zamoner Pacheco de, Santos, Adair Roberto Soares dos, Silva, Fátima Regina Mena Barreto
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Ltd 01-06-2010
• Subjects: 45Ca 2+ uptake; Amino acid accumulation; Amino Acids, Neutral - metabolism; Animals; Animals, Newborn; Biological Transport, Active - drug effects; Calcium - metabolism; Calcium Channels - metabolism; Cell Membrane - drug effects; Cell Membrane - metabolism; Cells, Cultured; Chloride Channels - metabolism; Ion channels; Male; Potassium Channels, Calcium-Activated - metabolism; Rats; Rats, Wistar; Testis; Testis - drug effects; Testis - metabolism; Testis - pathology; Thyroxine; Thyroxine - pharmacology; Testis; 45Ca 2+ uptake; Ion channels; Amino acid accumulation; Thyroxine
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/j.biocel.2010.03.015

Although the biological effects of thyroid hormones are mediated by nuclear receptors (genomic mechanisms), interactions with receptors associated with the plasma membrane (non-genomic mechanisms) of target cells are not clear. In this study we investigated the rapid stimulatory effect of thyroxine (T
4) on
45Ca
2+ uptake as well as ionic currents and intracellular messengers involved in the stimulatory action of T
4 in amino acid accumulation in immature rat testes. Results indicated that 10
−9
M or 10
−6
M T
4 was able to increase immediately
45Ca
2+ uptake after 60
s of hormone exposure. These results indicate for the first time that voltage-dependent Ca
2+ channels and ATP-dependent K
+ channels can be seen as a set-point in the stimulatory effect of T
4 on amino acid accumulation. Apamin-sensitive small-conductance Ca
2+-activated K
+ channels (SK
Ca) and chloride channels were shown to be partially involved in this mechanism. The amino acid accumulation triggered by the PKC pathway suggests a functional link between different ion channel activities and the stimulatory effect of T
4 on amino acid accumulation. In conclusion, we show in this study a rapid and stimulatory effect of T
4 on calcium uptake and on amino acid accumulation, both events initiated at the plasma membrane, which strongly characterizes a non-genomic effect of T
4 in immature rat testes.