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Calcium‐force coupling mechanisms during vasodilator‐induced relaxation of ferret aorta.
Author(s) -
DeFeo T T,
Morgan K G
Publication year - 1989
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1989.sp017607
Subject(s) - vasodilation , calcium , coupling (piping) , aorta , relaxation (psychology) , cardiology , chemistry , biophysics , medicine , materials science , biology , metallurgy
1. The effects of three vasodilators, nifedipine, hydralazine and forskolin, were determined on isometric force and intracellular ionized calcium concentration ([Ca2+]i) as indicated by aequorin in ferret aorta. Three types of contraction were studied: the intrinsic tone induced by warming from 22 to 37 degrees C; the contraction to the phorbol ester 12‐deoxyphorbol‐13‐isobutyrate‐20‐acetate (DPBA); and the contraction to potassium depolarization. 2. On warming there was no significant steady‐state change in [Ca2+], even though 5.7 +/‐ 0.7 mN of tone developed. During potassium depolarization, [Ca2+]i rose to a sustained plateau while DPBA caused no significant rise in [Ca2+]i. 3. Nifedipine and hydralazine inhibited intrinsic tone while causing an associated decrease in [Ca2+]i; but in the presence of forskolin, a similar inhibition of tone was accompanied by no significant decrease in [Ca2+]i. 4. Nifedipine and hydralazine prolonged the characteristic lag phase before force development in response to DPBA but did not cause a significant change in contraction amplitude. In contrast, forskolin caused an essentially total inhibition of the contraction. 5. During potassium depolarization, all three vasodilators caused significant decreases in [Ca2+]i coincident with decreases in steady‐state force. Calcium‐force curves were constructed by plotting the calibrated aequorin light signal against the resulting force. The control calcium‐force curve was not shifted by nifedipine or hydralazine but was significantly shifted to the right by forskolin.