Effect of lovastatin on cholesterol content of cardiac and red blood cell membranes in normal and cardiomyopathic hamsters.

Lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A, is used therapeutically to lower plasma cholesterol levels. However, the effect of this therapy on cell membrane cholesterol in vivo is not known. The goal of this study was to investigate whether lovastatin treatment of hamsters decreases cholesterol in cardiac cell membranes and in red blood cell (RBC) membranes. Because abnormal cellular Ca++ regulation has been associated with altered membrane cholesterol in hearts of cardiomyopathic (CM) hamsters, we also measured the cholesterol content of cardiac and RBC membranes from lovastatin-treated and untreated Bio 14.6 CM hamsters to determine whether any differences existed with respect to normals. Sarcolemma-enriched cardiac membranes and RBC membranes were obtained from 42 to 45-day normal and CM hamsters after 13 days of lovastatin treatment (0.1% of food/day) and from untreated normal and CM hamsters. Plasma cholesterol, membrane cholesterol/phospholipid (C/PL) ratio and cholesterol per milligram of membrane protein (C/prot) were determined. In hearts from untreated CM hamsters, C/prot was significantly lower (P < .05) than in untreated normals. Lovastatin decreased plasma cholesterol by 76% and 81% in normal and CM hamsters, respectively (P < .001), but after lovastatin treatment, there was no significant change in C/PL or C/prot in cardiac membranes from either strain; there was also no significant decrease in C/prot or in C/PL of RBC membranes from normals or C/PL of CM hamster RBC membranes. However, lovastatin feeding resulted in a significant (P < .01) 24% decrease in C/prot of CM RBC membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Subcellular calcium content in cardiomyopathic hamster hearts in vivo: an electron probe study.

In the Syrian cardiomyopathic hamster heart, abnormal cellular calcium regulation, resulting in cellular calcium overload, is believed to play a role in the pathogenesis of cardiac hypertrophy and failure. Alternatively, the primary abnormality may be coronary vasospasm, resulting in reperfusion-induced necrosis. According to the latter hypothesis, only those cells that suffer an ischemic insult would contain elevated calcium levels. To determine whether a generalized elevation in myocytic calcium exists in myopathic hamster hearts, we measured cellular and subcellular calcium concentrations by electron probe microanalysis in cryosections of 50-day and 96-day myopathic and control hearts, rapidly frozen in vivo. Total calcium content of ventricular homogenates from each group was also measured by atomic absorption spectrophotometry. No significant differences in subcellular calcium were found by electron probe microanalysis among 50-day and 96-day myopathics and their age-matched controls. In 50-day myopathic and control hearts, mitochondrial calcium was 0.7 +/- 0.2 and 0.9 +/- 0.2, respectively, and A-band calcium was 3.0 +/- 0.4 and 2.6 +/- 0.4 mmol calcium/kg dry wt(+/- SEM). Results from 96-day animals were similar. Localized regions of elevated calcium were found only at sites of necrotic foci: in Na+-loaded cells (mitochondria: 4.7 +/- 1.3 (SEM) mmol/kg dry wt), in dying cells (mitochondria: 72 +/- 22 (SEM) mmol/kg dry wt) or as extracellular deposits (7-10 mol/kg dry wt). Total calcium content of hearts from myopathic hamsters, as determined by atomic absorption spectrophotometry, was also 13 times (50-day) and 50 times (96-day) higher than controls. These results demonstrate that there is a marked heterogeneity in cellular calcium content in myopathic hamster hearts, but the data do not support the hypothesis of a generalized cellular calcium overload.