The breeding for development of myocardial infarction in WHHL rabbits

渡边遗传性高脂血症（WHHL）兔从出生起就表现出高脂血症，这是由于低密度脂蛋白受体的遗传缺陷。这种动物的主动脉和冠状动脉粥样硬化发生在过早的年龄。然而，心肌梗死在幼兔中并不常见。我们进行了选择性育种，试图在WHHL兔中增加这种疾病的发生率。本研究将88只选择育种后的家兔（mi系）与93只选择育种前的家兔（非mi系）进行对比，以评估育种效果。结果如下：1)。非mi系平均窄化率为56%，F1系为66%，F3系为77%，F4系为78%。2)。75%以上狭窄的频率在非mi系中为26%，在mi系中F1为41%，F3为67%，F4为75%。3）. 非mi线心肌梗死发生率为13%，mi线F1组为15%，F3组为26%，F4组为25%。4)。10月龄以上引起心肌梗死的WHHL家兔冠状动脉狭窄均超过75%，而10月龄以下家兔心肌梗死与冠状动脉严重狭窄无相关性。5)。公兔心肌梗死发生率明显高于母兔。因此，我们认为冠状动脉狭窄和心肌梗死都是由于选择性育种而扩大的。

The Watanabe heritable hyperlipidemic (WHHL) rabbit shows hyperlipidemia from birth, owing to a genetical deficiency of the low density lipoprotein receptors. The aortic and coronary atheros-clerosis occur at a premature age in this animal. However, myocardial infarction does not develop often in the yound rabbits. We carried out selective breeding in an attempt to increase in the incidence of this lision in WHHL rabbits. In this study 88 rabbits after selective breeding (MI-line) sere compored with 93 rabbits before selective breeding (non MI-line) in order to estimate the breeding effect. The results were as follows : 1). The average of the percent of narrowing was 56% in non MI-line, 66% in F1 of MI-line, 77% in F3 of MI-line and 78% in F4 of MI-line. 2). The frequency of over 75% narrowing was 26% in non MI-line and increased to 41% in F1, 67% in F3 and 75% in F4 of MI-line. 3). The incidence in myocardial infarction was 13% in non MI-line and increased to 15% in F1, 26% in F3 and 25% in F4 of MI-line. 4). WHHL rabbits aged over 10 months in which myocardial infarction provoked were always observed over 75% narrowing in coronary arteries, whereas in the rabbits aged under 10 months there were no relation between myocardial infarction and the severe coronary narrowing. 5). The incidence of myocardial infarction in the male rabbits was significantly higher than that in the female. Consequently, we considered that both coronary narrowing and myocardial infarction were expanded because of the selective breeding.