Date of Award

7-1-1996

Document Type

Thesis

Degree Name

Master of Arts (MA)

Department

Biology

First Advisor

Dr. Robert S. Egan

Abstract

Extracts from Letharia vulpina, Umbilicaria americana, Cladina subtenuis, Xanthoparmelia cumberlandia, Rimelia reticulata, and Parmotrema austrosinense were used to study their electrophysiological effects on rat heart ventricular tissue. Additionally, solutions of four purified lichen metabolites ---- vulpinic acid, usnic acid, stictic acid, and atranorin ---- were studied in the same manner. The action potential duration at 50% and 90% of repolarization was significantly reduced by two of the extracts and metabolites, those containing vulpinic acid and usnic acid and the purified forms of those compounds. A positive relationship between the effects of extracts and purified compounds was exhibited. These data suggest that the active metabolites may depress inward calcium current or enhance outward potassium currents. However, when single, dissociated rat myocytes were exposed to vulpinic acid, activation of an ATP-sensitive potassium channel was observed, and this was blocked with glibenclamide, a specific blocker of that channel. This ATP-sensitive potassium channel created an overlapping current which made it appear that an inward calcium current or outward repolarizing currents were affected, when in fact they were not.

Comments

A Thesis Presented to the Department of Biology and the Faculty of the Graduate College University of Nebraska In Partial Fulfillment of the Requirements for the Degree Master of Arts University of Nebraska at Omaha. Copyright 1996 Richard C. Witt.

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