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Voltage-activated ionic currents in goldfish pituitary cells.
Gen Comp Endocrinol. 1993 Oct; 92(1):16-30.GC

Abstract

The release of gonadotropin and growth hormone from goldfish pituitary cells has been shown to be dependent on the entry of extracellular Ca2+ through voltage-sensitive Ca2+ channels by pharmacological studies. As a first step to further investigate the involvement of voltage-dependent ion channels in the regulation of anterior pituitary hormone release in the goldfish, cell excitability and voltage-dependent ion currents were characterized using tight-seal whole-cell recordings in dispersed goldfish pituitary cells. Cultured goldfish pituitary cells had an average membrane potential of -36 +/- 3 mV. When held at membrane potentials more negative than -60 mV, these cells were excitable, responding to depolarizing current pulses or anode break with the firing of single action potentials. Results from total current voltage-clamp recordings suggested that all goldfish pituitary cells possess voltage-dependent Na+, Ca2+, and K+ currents. These currents were further characterized independently under isolated current recording conditions. The rapid, transient Na+ current activated at voltages more positive than -40 mV and was sensitive to tetrodotoxin. The steady state inactivation of this Na+ current was also voltage-dependent; at the measured resting potential, > or = 50% of the Na+ current was not available for activation. The voltage-dependence and activation kinetics of the tetraethylammonium-sensitive K+ current resembled those of the delayed rectifier K+ current. The K+ current activated slowly at potentials more positive than -40 mV, and showed little inactivation over the duration of a 1-sec depolarizing pulse. Steady-state inactivation characteristics indicated that < 50% of the K+ current was inactivated at resting potentials. Experiments with 4-aminopyridine indicated the presence of an early transient K+ current that activated in a similar voltage range as the delayed rectifier current. Using barium as the charge carrier to measure Ca2+ currents, a high-voltage activated, long-lasting Ca2+ current was revealed. This "L-type" Ca2+ current activated at potentials more positive than -30 mV and was inhibited by verapamil and nifedipine. This study indicates that goldfish pituitary cells possess the electrophysiological properties required for the participation of voltage-sensitive ion channels in the regulation of hormone release.

Authors+Show Affiliations

Department of Zoology, University of Alberta, Edmonton, Canada.No affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

7505247

Citation

Price, C J., et al. "Voltage-activated Ionic Currents in Goldfish Pituitary Cells." General and Comparative Endocrinology, vol. 92, no. 1, 1993, pp. 16-30.
Price CJ, Goldberg JI, Chang JP. Voltage-activated ionic currents in goldfish pituitary cells. Gen Comp Endocrinol. 1993;92(1):16-30.
Price, C. J., Goldberg, J. I., & Chang, J. P. (1993). Voltage-activated ionic currents in goldfish pituitary cells. General and Comparative Endocrinology, 92(1), 16-30.
Price CJ, Goldberg JI, Chang JP. Voltage-activated Ionic Currents in Goldfish Pituitary Cells. Gen Comp Endocrinol. 1993;92(1):16-30. PubMed PMID: 7505247.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Voltage-activated ionic currents in goldfish pituitary cells. AU - Price,C J, AU - Goldberg,J I, AU - Chang,J P, PY - 1993/10/1/pubmed PY - 1993/10/1/medline PY - 1993/10/1/entrez SP - 16 EP - 30 JF - General and comparative endocrinology JO - Gen Comp Endocrinol VL - 92 IS - 1 N2 - The release of gonadotropin and growth hormone from goldfish pituitary cells has been shown to be dependent on the entry of extracellular Ca2+ through voltage-sensitive Ca2+ channels by pharmacological studies. As a first step to further investigate the involvement of voltage-dependent ion channels in the regulation of anterior pituitary hormone release in the goldfish, cell excitability and voltage-dependent ion currents were characterized using tight-seal whole-cell recordings in dispersed goldfish pituitary cells. Cultured goldfish pituitary cells had an average membrane potential of -36 +/- 3 mV. When held at membrane potentials more negative than -60 mV, these cells were excitable, responding to depolarizing current pulses or anode break with the firing of single action potentials. Results from total current voltage-clamp recordings suggested that all goldfish pituitary cells possess voltage-dependent Na+, Ca2+, and K+ currents. These currents were further characterized independently under isolated current recording conditions. The rapid, transient Na+ current activated at voltages more positive than -40 mV and was sensitive to tetrodotoxin. The steady state inactivation of this Na+ current was also voltage-dependent; at the measured resting potential, > or = 50% of the Na+ current was not available for activation. The voltage-dependence and activation kinetics of the tetraethylammonium-sensitive K+ current resembled those of the delayed rectifier K+ current. The K+ current activated slowly at potentials more positive than -40 mV, and showed little inactivation over the duration of a 1-sec depolarizing pulse. Steady-state inactivation characteristics indicated that < 50% of the K+ current was inactivated at resting potentials. Experiments with 4-aminopyridine indicated the presence of an early transient K+ current that activated in a similar voltage range as the delayed rectifier current. Using barium as the charge carrier to measure Ca2+ currents, a high-voltage activated, long-lasting Ca2+ current was revealed. This "L-type" Ca2+ current activated at potentials more positive than -30 mV and was inhibited by verapamil and nifedipine. This study indicates that goldfish pituitary cells possess the electrophysiological properties required for the participation of voltage-sensitive ion channels in the regulation of hormone release. SN - 0016-6480 UR - https://www.unboundmedicine.com/medline/citation/7505247/Voltage_activated_ionic_currents_in_goldfish_pituitary_cells_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0016-6480(83)71139-1 DB - PRIME DP - Unbound Medicine ER -