Defense Date

2012

Document Type

Thesis

Degree Name

Master of Science

Department

Pharmacology & Toxicology

First Advisor

Hamid Akbarali

Abstract

The ATP sensitive potassium channel (KATP) in mouse colonic smooth muscle cell is a complex containing a pore forming subunit (Kir6.1) and a sulfonyl urea receptor subunit (SUR2B). These channels are responsible for maintaining the cellular excitability of the smooth muscle cell which in turn regulates the motility patterns in the colon. We used whole-cell voltage-clamp techniques to study the alterations in these channels in smooth muscle cells in experimental model of colitis (colonic inflammation). Colitis was induced in BALB/C mice following an intracolonic administration of trinitrobenzene sulfonic acid (TNBS). KATP currents were measured at Vh -60 mV in high K+ external solution. The dose-response to levcromakalim (LEVC), a KATP channel opener, was significantly shifted to the left in the inflamed smooth muscle cells. Both the affinity and maximal currents induced by LEV were enhanced in inflammation. The EC50 in control was 6259 nM (n=10) and 422 nM (n=8) in inflamed colon while the maximal currents were 9.9 ± 0.71 pA/pF (60 μM) in control and 39.7 ± 8.8 pA/pF (3 μM) following inflammation. Similar to LEVC, KATP currents activated by sodium hydrogen sulfide (NaHS) (10-1000 μM) were significantly greater in inflamed compared to controls. In control cells, pretreatment with 100 µM NaHS shifted the EC50 for LEV-induced currents from 2838 nM (n=6) to 154 nM (n=8). These data suggest that NaHS can act as an allosteric modulator for LEV-induced KATP currents. Decreased colonic motility may result from enhanced KATP activation by increased release of H2S in colitis.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

May 2012

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