Propranolol diminishes cardiac hypertrophy but does not abolish acceleration of the ischemic contracture in hyperthyroid hearts.
ABSTRACT This study was undertaken to define the contributions of left ventricular hypertrophy (LVH) and increased adrenergic activity to the acceleration of ischemic contracture (IC) that occurs in chronic hyperthyroid rat heart. Acute and chronic hyperthyroidism (THYR) were induced by thyroxine administration for 2 and 14 days, respectively, and normal animals (NORM) served as controls. Isolated hearts were perfused in a Langendorff mode. NORM alpha acute, n = 6; THYR alpha acute, n = 8; and THYR alpha, n = 13; and NORM alpha, n = 13 were subjected to 20-min zero-flow global ischemia (I) and 45-min reperfusion (R). Additional THYR and NORM hearts treated with propranolol (prop) were subjected to 30-min I; THYR beta prop, n = 6 and NORM beta prop, n = 8, and THYR beta, n = 6, NORM beta, n = 8 served as controls. Acceleration of IC was measured by the time to peak contracture (Tmax). Left ventricular hypertrophy (LVH) was assessed by the ratio of left ventricular weight in milligrams (LVW) to animal body weight (BW) in grams. Cardiac hypertrophy developed in chronic but not acute hyperthyroidism. Propranolol reduced the extent of LVH. Contracture occurred earlier in chronic than in acute hyperthyroid and normal hearts. Propranolol did not alter contracture. In conclusion, IC is accelerated by thyroxine administration, and this is probably not due to LVH or increased beta-adrenergic activity. Propranolol diminishes LVH in hyperthyroidism.
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ABSTRACT: The effects of ATP, ADP, and adenosine in the processes of platelet aggregation, vasodilatation, and coronary flow have been known for many years. The sequential hydrolysis of ATP to adenosine by soluble nucleotidases constitutes the main system for rapid inactivation of circulating adenine nucleotides. Thyroid disorders affect a number of biological factors including adenosine levels in different fractions. Then, we intend to investigate if the soluble nucleotidases responsible for the ATP, ADP, and AMP hydrolysis are affected by variations in the thyroid hormone levels in blood serum from adult rats. Hyperthyroidism was induced by daily intraperitoneal injections of L-thyroxine (T4) (2.5 and 10.0 μg/100 g body weight, respectively) for 7 or 14 days. Hypothyroidism was induced by thyroidectomy and methimazole (0.05%) added to their drinking water during 7 or 14 days. The treatments efficacy was confirmed by determination of hemodynamic parameters and cardiac hypertrophy evaluation. T4 treatment predominantly inhibited, and hypothyroidism (14 days after thyroidectomy) predominantly increased the ATP, ADP, and AMP hydrolysis in rat blood serum. These results suggest that both excess and deficiency of thyroid hormones can modulate the ATP diphosphohydrolase and 5'-nucleotidase activities in rat blood serum and consequently modulate the effects mediated by these enzymes and their products in vascular system.BioFactors 01/2011; 37(1):40-5. DOI:10.1002/biof.133 · 3.00 Impact Factor
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ABSTRACT: The present study investigated the response of the hypothyroid heart to ischaemia-reperfusion. Hypothyroidism was induced in Wistar rats by oral administration of propylthiouracil (0.05%) for 3 weeks (HYPO rats), while normal animals (NORM) served as controls. Isolated hearts from NORM and HYPO animals were perfused in Langendorff mode and subjected to zero-flow global ischaemia followed by reperfusion (I/R). Post-ischaemic recovery of left ventricular developed pressure was expressed as % of the initial value (LVDP%). Basal expression of protein kinase C epsilon (PKCepsilon) and PKCdelta and phosphorylation of p46 and p54 c-jun NH(2)-terminal kinases (JNKs) in response to I/R were assessed by Western blotting. LVDP% was found to be significantly higher in HYPO hearts than in NORM. At baseline, PKCepsilon expression was 1.4-fold more in HYPO than in NORM hearts, P<0.05, while PKCdelta was not changed. Furthermore, basal phospho-p54 and -p46 JNK levels were 2.2- and 2.6-fold more in HYPO than in NORM hearts, P<0.05. In response to I/R, in NORM hearts, phospho-p54 and -p46 JNK levels were 5.5- and 6.0-fold more as compared with the baseline values, P<0.05, while they were not significantly altered in HYPO hearts. HYPO hearts seem to display a phenotype of cardioprotection against ischaemia-reperfusion and this is associated with basal PKCepsilon overexpression and attenuated JNK activation after I/R.Journal of Endocrinology 10/2003; 178(3):427-35. · 3.59 Impact Factor
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ABSTRACT: The present study was undertaken to investigate heat stress protein (HSP)-70 mRNA induction and p38 MAP kinase (MAPK) activity in response to ischaemic stress in the hyperthyroid rat heart. L-Thyroxine (T(4)) (25 microg/100 g body weight) was administered to Wistar rats for 2 days (THYRacute) or 14 days (THYR), while animals treated similarly with normal saline served as controls (NORMacute and NORM). In addition, abdominal aortic banding was performed in another group of rats to produce constriction-induced hypertrophy (HYP), while sham-operated (SOP) animals served as controls. Isolated rat hearts were perfused in a Langendorff mode. Hearts from NORMacute (n=6), THYRacute animals (n=8), NORM (n=6), THYR (n=6), SOP (n=5) and HYP (n=7) animals were subjected to 20 min of zero-flow global ischaemia followed by 45 min of reperfusion. HSP70 mRNA expression and phosphorylated p38 MAPK protein expression were detected in response to ischaemia and protein kinase C-epsilon (PKCepsilon) protein expression was detected at baseline. Thyroid hormones were measured in plasma. Long-term T(4) administration and aortic constriction resulted in the development of cardiac hypertrophy. Thyroid hormones were increased in both THYR and THYRacute as compared with normal groups (P<0.05). HSP70 mRNA induction was increased 2.3-fold in THYR as compared with NORM hearts (P<0.05), whereas there was not any difference between THYRacute and NORMacute hearts (P>0.05). Phosphorylated p38 MAPK protein expression was 2.2-fold more in NORM than in THYR hearts (P<0.05), but it was not different between NORMacute and THYRacute hearts (P>0.05). HSP70 mRNA induction was 1.8-fold greater in HYP than in SOP hearts (P<0.05), whereas phosphorylated p38 MAPK protein expression was similar between the two groups (P>0.05). PKCepsilon protein expression at baseline was 1.7-fold more in NORM than in THYR hearts (P<0.05), and not different between NORMacute and THYRacute hearts (P>0.05) as well as HYP and SOP hearts (P>0.05). This study shows that HSP70 mRNA expression is increased, whereas p38 MAPK activation is attenuated in response to ischaemia in long-term T(4)-treated rat hearts as compared with normal and acute hyperthyroid hearts.Journal of Endocrinology 07/2001; 170(1):207-15. · 3.59 Impact Factor