Abstract
We have previously reported results of studies on the hearts of rats with two types of uremia (1, 2): (1) severe acute uremia created by bilateral nephrectomy, and (2) moderate uremia created by 5/6 nephrectomy. In the former case hearts were studied 24 hr after nephrectomy and in the latter, 2 weeks after surgery.
When hearts of rats with severe acute uremia were studied in an isolated heart apparatus, their performance was the same as control hearts. Under the same conditions, hearts of rats with moderate uremia show enhanced contractile responses. On the other hand, hearts of acute uremic rats studied in vivo were found to have greater contractile responses to gradual aortic occlusion than did hearts of sham operated animals (2). The present investigation was designed to determined if hearts from animals prepared with 5/6 nephrectomy show the same increased responses in vivo that they do in vitro, and to study the time course of the effect of uremia on the heart.
Methods. Male Wistar rats weighing 250-300 g were anesthetized with ether, and 5/6 nephrectomy was performed taking care not to remove the adrenal glands (1). Sham operated rats were used as controls. For the 24 hr prior to study the rats were fasted but allowed to drink water. For the study, the rats were anesthetized with intraperitoneal pentobarbital (60 mg/kg). Respiration was controlled via a tracheostomy by a Harvard small animal respirator. To study cardiac performance complete aortic occlusion was produced in the open chest animal as described previously (2). Left ventricular pressure was measured by a 17 cm long PE catheter which punctured the apex of the left ventricle, and low and high gain tracings for systolic and diastolic pressures were recorded with an Electronics for Medicine VR6 multichannel recorder.
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