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Characterization of an inwardly rectifying potassium channel in the rabbit superior lacrimal gland.
Invest Ophthalmol Vis Sci. 1998 Feb; 39(2):308-14.IO

Abstract

PURPOSE

To characterize the properties of an inwardly rectifying K+ (KIR) current in fresh, enzymatically isolated acinar cells from the rabbit superior lacrimal gland.

METHODS

New Zealand White rabbits of both sexes were killed by injecting 45 mg/kg pentobarbital sodium, and the glands were excised. Single acinar cells were isolated enzymatically from these glands. Standard patch-clamp techniques were used to record ion currents.

RESULTS

Hyperpolarizing voltages evoked KIR currents that had a conductance of 2.7 +/- 0.16 nS (n = 6) in the range -50 mV to -160 mV. The KIR current was activated with steep voltage dependence on hyperpolarization, and the conductance was approximately dependent on the square root of the external K+ concentration. Increasing the pipette Ca2+ concentration from 10(-9) M to 10(-6) M increased the conductance to 5.3 +/- 0.45 nS (n = 7). Internal substitution of K+ with various cations gave the following permeability sequence: K+ (1.0) > Rb+ (0.83) > Li+ (0.15). The KIR current was inhibited by Ba2+ (100 microns), tetraethylammonium (10 mM), and Cs+ (5 mM) but was insensitive to 4-aminopyridine (5 mM). The single-channel conductance was 43 +/- 2.7 pS (n = 11), and the relationship between between single-channel conductance (gamma) and external K+ concentration ([K]o) is given by: gamma = 7.04[K]o0.37 (pS, r2 = 0.99, P < 0.05). The relationship between [K]o and zero current potential (Erev) is given by: Erev = 35.5 log[K]o - 77.8 (mV; r2 = 0.99, P < 0.05).

CONCLUSIONS

The KIR current identified in these lacrimal acini has a similar dependence on [K]o as other inward rectifiers of excitable tissues and exocrine glands. However, this study highlights that there are interspecies variations and similarities between KIR channels that could be related to their individual physiological roles. The authors' investigations suggest that one role of the KIR channel in the rabbit superior lacrimal gland acinar cells is to set and stabilize the resting membrane potential. However, this KIR channel may also be involved in secretion, as has been shown to occur in the sheep parotid gland.

Authors+Show Affiliations

Co-operative Research Centre for Eye Research and Technology, University of New South Wales, Kensington, Australia.No affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article

Language

eng

PubMed ID

9477987

Citation

Herok, G H., et al. "Characterization of an Inwardly Rectifying Potassium Channel in the Rabbit Superior Lacrimal Gland." Investigative Ophthalmology & Visual Science, vol. 39, no. 2, 1998, pp. 308-14.
Herok GH, Millar TJ, Anderton PJ, et al. Characterization of an inwardly rectifying potassium channel in the rabbit superior lacrimal gland. Invest Ophthalmol Vis Sci. 1998;39(2):308-14.
Herok, G. H., Millar, T. J., Anderton, P. J., & Martin, D. K. (1998). Characterization of an inwardly rectifying potassium channel in the rabbit superior lacrimal gland. Investigative Ophthalmology & Visual Science, 39(2), 308-14.
Herok GH, et al. Characterization of an Inwardly Rectifying Potassium Channel in the Rabbit Superior Lacrimal Gland. Invest Ophthalmol Vis Sci. 1998;39(2):308-14. PubMed PMID: 9477987.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Characterization of an inwardly rectifying potassium channel in the rabbit superior lacrimal gland. AU - Herok,G H, AU - Millar,T J, AU - Anderton,P J, AU - Martin,D K, PY - 1998/3/7/pubmed PY - 1998/3/7/medline PY - 1998/3/7/entrez SP - 308 EP - 14 JF - Investigative ophthalmology & visual science JO - Invest Ophthalmol Vis Sci VL - 39 IS - 2 N2 - PURPOSE: To characterize the properties of an inwardly rectifying K+ (KIR) current in fresh, enzymatically isolated acinar cells from the rabbit superior lacrimal gland. METHODS: New Zealand White rabbits of both sexes were killed by injecting 45 mg/kg pentobarbital sodium, and the glands were excised. Single acinar cells were isolated enzymatically from these glands. Standard patch-clamp techniques were used to record ion currents. RESULTS: Hyperpolarizing voltages evoked KIR currents that had a conductance of 2.7 +/- 0.16 nS (n = 6) in the range -50 mV to -160 mV. The KIR current was activated with steep voltage dependence on hyperpolarization, and the conductance was approximately dependent on the square root of the external K+ concentration. Increasing the pipette Ca2+ concentration from 10(-9) M to 10(-6) M increased the conductance to 5.3 +/- 0.45 nS (n = 7). Internal substitution of K+ with various cations gave the following permeability sequence: K+ (1.0) > Rb+ (0.83) > Li+ (0.15). The KIR current was inhibited by Ba2+ (100 microns), tetraethylammonium (10 mM), and Cs+ (5 mM) but was insensitive to 4-aminopyridine (5 mM). The single-channel conductance was 43 +/- 2.7 pS (n = 11), and the relationship between between single-channel conductance (gamma) and external K+ concentration ([K]o) is given by: gamma = 7.04[K]o0.37 (pS, r2 = 0.99, P < 0.05). The relationship between [K]o and zero current potential (Erev) is given by: Erev = 35.5 log[K]o - 77.8 (mV; r2 = 0.99, P < 0.05). CONCLUSIONS: The KIR current identified in these lacrimal acini has a similar dependence on [K]o as other inward rectifiers of excitable tissues and exocrine glands. However, this study highlights that there are interspecies variations and similarities between KIR channels that could be related to their individual physiological roles. The authors' investigations suggest that one role of the KIR channel in the rabbit superior lacrimal gland acinar cells is to set and stabilize the resting membrane potential. However, this KIR channel may also be involved in secretion, as has been shown to occur in the sheep parotid gland. SN - 0146-0404 UR - https://www.unboundmedicine.com/medline/citation/9477987/Characterization_of_an_inwardly_rectifying_potassium_channel_in_the_rabbit_superior_lacrimal_gland_ L2 - https://iovs.arvojournals.org/article.aspx?volume=39&amp;issue=2&amp;page=308 DB - PRIME DP - Unbound Medicine ER -