Effects of 2,5-di(tert-butyl)-1-4-benzohydroquinone (tbq) on rat
cardiac muscle contractility.
Kabbara, Akram A., and D. George Stephenson.
SCHOOL OF ZOOLOGY, FACULTY OF SCIENCE AND TECHNOLOGY, LA TROBE
UNIVERSITY, BUNDOORA, VICTORIA 3083, AUSTRALIA
APStracts 3:0387H, 1996.
The effects of 2,5-di(tert-butyl)-1-4-benzohydroquinone (TBQ) on
cardiac muscle contractility have been investigated using cardiac
preparations from the right ventricle of the rat. In saponin-skinned
preparations, TBQ (50 and 100 [mu]M) did not significantly affect the
maximal isometric Ca2+-activated force or the steady-state force
-[Ca2+] relation but significantly reduced the Ca2+ content of the
sarcoplasmic reticulum (SR) both in the absence and in the presence
of 50 [mu]M of the SR Ca2+-release channel blocker ruthenium red. The
effect of TBQ on SR Ca2+ content was not due to an increased passive
Ca2+ leak or Ca2+-induced Ca2+ release from the SR but to the
specific inhibition of the SR Ca2+ pump. In electrically stimulated
(0.2 Hz, 23 oC) intact cardiac preparations loaded with the Ca2+
-sensitive fluorescent dye fura-2, TBQ (50 and 100 [mu]M) caused the
decrease in the rates of rise and fall of the fura-2 signal (ratio of
fluorescence intensities at 360 and 380 nm excitation) and isometric
force. In the presence of 50 and 100 [mu]M TBQ the twitch height of
the isometric force response was significantly decreased, whereas the
peak of the fura-2 signal was not significantly affected. At 2 Hz
stimulation frequency, both parameters were reduced in the presence
of 50 and 100 [mu]M TBQ. Taken together, the results obtained in this
study show that TBQ inhibits rather specifically the SR Ca2+ uptake
in the rat ventricle and that it can be used as a tool to determine
the function of the SR under different conditions.
Received 29 April 1996; accepted in final form 27 August 1996.
APS Manuscript Number H375-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996