@article{3052025,
    title = "Hyperthyroidism is associated with preserved preconditioning capacity
but intensified and accelerated ischaemic contracture in rat heart",
    author = "Pantos, CI and Cokkinos, DD and Tzeis, SM and Malliopoulou, V and and Mourouzis, IS and Carageorgiou, HC and Limas, C and Varonos, DV and and Cokkinos, DV",
    journal = "Basic Research in Cardiology",
    year = "1999",
    volume = "94",
    number = "4",
    pages = "254-260",
    publisher = "Springer Berlin Heidelberg",
    issn = "0300-8428, 1435-1803",
    doi = "10.1007/s003950050150",
    keywords = "hyperthyroidism; ischaemic contracture; ischaemic preconditioning;
isolated rat heart",
    abstract = "Background: The present study was undertaken to define the effects of
thyroxine administration on ischaemic preconditioning (PC) and the
ischaemic contracture. Methods: Hyperthyroidism was induced by
administration of L-thyroxine in rats (THYR) while normal animals served
as controls (NORMa). Isolated rat hearts were perfused in a Langendorff
preparation. NORMa control (n = 16) and THYR control (n = 9) hearts
underwent 20 min of ischaemia and 45 min reperfusion while NORMa PC (n =
16) and THYR PC (n = 14) were subjected to PC before ischaemia.
Additional normal hearts were subjected to 30 min of ischaemia with and
without PC, NORMb control, n = 8 and NORMb PC, n = 6. Postischaemic
recoveries of left ventricular (LV) developed pressure were expressed as
% of the initial value (LVDP%). Severity of contracture was measured
by the time (Tmax) and magnitude (Cmax) of peak contracture. Results:
LVDP% was significantly higher after PC, both in NORMa and THYR rats.
In NORMa control hearts, ischaemic contracture had not yet reached a
plateau at 20 min of ischaemia. Contracture appeared earlier in THYR
control and PC than in NORMa control and PC groups. Tmax was 22.1 (0.9)
vs 16.8 (1.4) min for NORMb control and PC, p < 0.05 and 12.5 (1.0) vs
9.3 (1.1) min for THYR control and PC hearts, p < 0.05. Tmax was earlier
in both THYR groups compared to NORMb groups, p < 0.05. Cmax was
significantly higher in both THYR groups compared to both NORMb groups.
Conclusion: Ischaemic contracture is both accelerated and accentuated in
thyroxine treated hearts while preconditioning capacity is preserved.
Preconditioning and thyroxine administration shorten Tmax in an additive
way, whereas Cmax in hyperthyroid hearts did not further increase by
preconditioning."
}