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This Article Full Text Full Text (PDF) All Versions of this Article: 573/2/453    most recent jphysiol.2006.107375v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Beckett, E. A. H. Articles by Don Koh, S. Search for Related Content PubMed PubMed Citation Articles by Beckett, E. A. H. Articles by Don Koh, S. Related Collections Cardiovascular

¹ Department of Physiology and Cell Biology, University of Nevada School of Medicine, MS 352, Reno, NV 89557, USA

Idiopathic constipation is higher in women of reproductive age than postmenopausal women or men, suggesting that female steroid hormones influence gastrointestinal motility. How female hormones affect motility is unclear. Colonic motility is regulated by ion channels in colonic myocytes. Voltage-dependent K⁺ channels serve to set the excitability of colonic muscles. We investigated regulation of Kv4.3 channel expression in response to acute or chronic changes in female hormones. Patch clamp experiments and quantitative PCR were used to compare outward currents and transcript expression in colonic myocytes from male, non-pregnant, pregnant and ovariectomized mice. Groups of ovariectomized mice received injections of oestrogen or progesterone to investigate the effects of hormone replacement. The capacitance of colonic myocytes from non-pregnant females was larger than in males. Net outward current density in male and ovariectomized mice was higher than in non-pregnant females and oestrogen-treated ovariectomized mice. Current densities in late pregnancy were lower than in female controls. Progesterone had no effect on outward currents. A-type currents were decreased in non-pregnant females compared with ovariectomized mice, and were further decreased by pregnancy or oestrogen replacement. Kv4.3 transcripts did not differ significantly between groups; however, expression of the potassium channel interacting protein KChIP1 was elevated in ovariectomized mice compared with female controls and oestrogen-treated ovariectomized mice. Delayed rectifier currents were not affected by oestrogen. In the mouse colon, oestrogen suppresses A-type currents, which are important for regulating excitability. These observations suggest a possible link between female hormones and altered colonic motility associated with menses, pregnancy and menopause.

(Received 10 February 2006; accepted after revision 26 March 2006; first published online 31 March 2006)
Corresponding author S. D. Koh: Department of Physiology and Cell Biology, University of Nevada School of Medicine, MS 352, Reno, NV 89557, USA. Email: sdk{at}physiology.unr.edu

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