title: Involvement of K+ channels and calcium-dependent pathways in the action of T3 on amino acid accumulation and membrane potential in Sertoli cells of immature rat testis.
abstract: The purpose of this study was to investigate the involvement of calcium in K+ currents and its effects on amino acid accumulation and on the membrane potential regulated by tri-iodo-L-thyronine (T3) in Sertoli cells. Immature rat testes were pre-incubated for 30 min in Krebs-Ringer bicarbonate buffer and incubated for 60 min in the presence of [14C]methylaminoisobutyric acid with and without T3 or T4 (dose-response curve). Specific channel blockers or chelating agents were added at different concentrations during pre-incubation and incubation periods to study the basal amino acid accumulation and a selected concentration of each drug was chosen to analyze the influence on the stimulatory hormone action. All amino acid accumulation experiments were carried out in a Dubnoff metabolic incubator at 32 degrees C, pH 7.4 and gassed with O2:CO2 (95:5; v/v). Seminiferous tubules from immature Sertoli cell-enriched testes were used for the electrophysiology experiments. Intracellular recording of the Sertoli cells was carried out in a chamber perfused with KRb with/without T3, T4 or blockers and the membrane potential was monitored. We found that T3 and T4 stimulated alpha-[1-14C] methylaminoisobutyric acid accumulation in immature rat testes and induced a membrane hyperpolarization in Sertoli cells. The action of T3 on amino acid accumulation and on the hyperpolarizing effect was inhibited by the K(+)-ATP channel blocker tolbutamide as well as the voltage-dependent Ca2+ channel blocker verapamil. These results clearly demonstrate for the first time the existence of an ionic mechanism related to Ca2+ and K+ fluxes in the rapid, nongenomic action of T3.
authors.affiliation: Departamento de Bioquímica, Centro de Ciências Biológicas, UFSC, Campus Universitário, Bairro Trindade, Cx Postal 5069, CEP: 88040-970 - Florianópolis, Santa Catarina, Brazil.
authors.forename: Karine Cunha
authors.initials: KC
authors.lastname: Volpato
authors.forename: Danusa
authors.initials: D
authors.lastname: Menegaz
authors.forename: Laura Difini
authors.initials: LD
authors.lastname: Leite
authors.forename: Kátia Padilha
authors.initials: KP
authors.lastname: Barreto
authors.forename: Euler
authors.initials: E
authors.lastname: de Vilhena Garcia
authors.forename: Fátima Regina Mena Barreto
authors.initials: FR
authors.lastname: Silva
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012708:Sertoli Cells / Q000187:drug effects / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D013974:Thyroxine / Q000494:pharmacology; D014044:Tolbutamide / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D000596:Amino Acids; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D014284:Triiodothyronine; D015091:beta-Alanine; C012924:2,2-dimethyl-beta-alanine; D004533:Egtazic Acid; D014044:Tolbutamide; D014700:Verapamil; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D013974:Thyroxine