General papers
Experimental hyperlipidemia prevents the protective effect of ischemic preconditioning on the contractility and responsiveness to phenylephrine of rat-isolated stunned papillary muscle

https://doi.org/10.1016/S0306-3623(99)00017-8Get rights and content

Abstract

This study was designed to establish a hyperlipidemic diet (significant increase in the cholesterol and triglycerides blood levels, but without atherogenic changes in heart muscle and coronary vessels) and to investigate the influence of experimental hyperlipidemia on the effects of ischemic preconditioning (PC) of rat-isolated papillary muscle on the time course of contractility during simulated ischemia and reperfusion and responsiveness to phenylephrine under such a condition. The animals were divided in four experimental groups: standard diet-fed control group (SD), SD underwent ischemic preconditioning (SD-PC), hyperlipidemic diet-fed group (HLD) and HLD undervent PC (HLD-PC). Force of contraction (Fc), velocity of contraction (+dF/dt), and velocity of relaxation (−dF/dt) were measured. HLD preparations were more sensitive to ischemia then SD ones. PC, performed by 5-min perfusion with no-substrate solution gassing with 95% N2/5% CO2 in the presence of fast electrical stimulation, and 10 min of reperfusion with normal solution and rate of stimulation, significantly increased the resistence of isolated cardiac tissues to simulated ischemia in SD-PC group, but not in HLD-PC group. Negative inotropic action of phenylephrine occured in SD group of preparations after simulated-ischemia/reperfusion period was also prevented by PC. Therefore, we conclude that experimental hyperlipidemia significantly influenced the function of rat heart muscle including the higher sensitivity to ischemia and different reaction to the same PC procedure.

Section snippets

Animals

Albino-Wistar rats of either gender, weighing 180–220 g were used. The isolated cardiac tissues were divided in four experimental groups: (1) muscles obtained from standard diet-fed rats (SD), (2) SD preparations underwent PC, (3) muscles obtained from hyperlipidemic diet-fed rats (HLD), and (4) HLD muscles underwent PC. The rats were housed in wire mesh bottom cages (one animal per cage) and kept in standard laboratory conditions (12 h light-dark cycle, 21–24°C, humidity 50–55%), with food

Effects of diet on the cholesterol and triglyceride serum levels

Total serum cholesterol and serum triglyceride concentrations were determined in 8 animals from hyperlipidemic diet-fed rats (HLD) and 8 animals from standard diet-fed rats (SD), after 30 days of diet, using commercial biochemical tests. It has been found a significant increase either in level of cholesterol (63.4 ± 3 mg/dl in SD group vs. 82.3 ± 6 mg/dl, p < 0.05) or triglyceride (62.6 ± 13 mg/dl vs. 120.5 ± 22.5 mg/dl, p < 0.01).

Effects of the diet on the heart muscle and coronary vessels morphology

Using HE-staining 200X, we have compared the structure of

Discussion

The major finding of this study is that papillary muscles obtained from HLD rats have shown a lack of ability to be preconditioned by the PC procedure which rendered the cardiac tissue obtained from SD rats to be more resistent to ischemia regarding contractility and responsiveness to phenylephrine. It is not clear what the reason for this is. Apparent differences in time course of contractility and responsiveness to phenylephrine between papillary muscles obtained from SD- and HLD-fed rats

Acknowledgements

Authors are grateful to Dr. Ewa Wróblewska from the Department of Clinical Biochemistry, Medical University of Gdańsk, for determination of the serum cholesterol and triglyceride levels in rats. This study was partially supported by grant W-928 to I.K.

References (21)

There are more references available in the full text version of this article.

Cited by (0)

View full text