Stereological study on the rat heart in chronic alimentary thiamine deficiency--absence of myocardial changes despite starvation.

Young male Wistar rats were fed with a thiamine-free diet for 35 days. The growth of the thiamine-deficient animals was considerably suppressed, as compared to a pair-fed control group (body weights: 140.4 +/- 4.3 g v. 243.1 +/- 4.3 g). A weight-matched control group was therefore evaluated in addition. Histological and ultrastructural investigations of the hearts did not reveal any morphological abnormalities. Stereological analysis was performed on left ventricular papillary muscles. One-way analysis of variance showed significant differences of stereological parameters between the three groups which were not associated with significant linear contrasts between the thiamine-deficient group and the weight-matched control group. Thus, the changes are not to be related to direct effects of thiamine depletion on the myocardium. Conclusively, the data indicate that stereological parameters (ratios) of the myocardium depend on heart weight and body weight, respectively, and are changed during normal growth. Our stereological estimates disclosed alterations of the following parameters: numerical density of myocardial cell nuclei, length density and volume density of capillaries, surface density of outer mitochondrial membranes and surface-to-volume ratio of mitochondria, and volume density of myofibrils. Furthermore, relative heart weights decrease in normal growth. It is concluded that our experimental model of chronic alimentary thiamine deficiency was associated with a normal structure of the myocardium. All significant differences between the thiamine-deficient group and the control group are explained by body weight changes following starvation in chronic thiamine deficiency.