The measurement of cardiovascular, renal and gastrointestinal function and some effects of anaesthesia, burn injury, bile toxin and angiotensin in the rat

Chen, Chau-Fong (1980) The measurement of cardiovascular, renal and gastrointestinal function and some effects of anaesthesia, burn injury, bile toxin and angiotensin in the rat. University of Southampton, Doctoral Thesis.

Abstract

The cardiac output was measured in the rat by impedance cardiography, which is a non-invasive technique; this is very useful for taking measurements in small animals and in man, since it does not cause physiological disturbances. The accuracy of this method was tested by comparing it with the thermodilution method and with the electromagnetic flowmeter; good agreement was found in both cases. The cardiac output was then measured under various experimental conditions: haemorrhage, isoprenaline/angiotensin infusion, burn injury, and grass carp bile injection. The fall in cardiac output after burn injury was faster than predicted from existing theories. The sensitivity to angiotensin 11 was unaffected by dietary salt. A conscious rat preparation (with chronic cannulae in the carotid artery, jugular vein and urinary bladder) was developed for the study of cardiovascular and renal function. The effects of some intravenous anaesthetic agents were investigated (Althesin, ketamine, pentothal, pentobarbitone and Inactin). Cardiovascular and renal function were extremely susceptible to anaesthesia, but Althesin was found to cause the least disturbance, and the changes with Inactin were different from those with the other anaesthetic agents.(Sar-1, gly-8)-angiotensin 11 was infused into rats. This had only weak vasoconstrictor activity and did not cause sodium retention by the kidney. It did, however, inhibit the vasoconstrictor and sodium retaining actions of angiotensin II. These observations support the hypothesis that the sodium-retaining action of angiotensin 11 is dependant on its vasoconstrictor action; if angiontensin II does stimulate sodium transport then the mechanism differs from that in the gut. Burn injury was applied to the temporarily anaesthetised rat. It was observed that the gastric emptying time, the small intestinal propulsive motility and the colonic transit time were all slowed down, and saline resuscitation was shown to be beneficial. These serious changes in gastrointestinal mobility after burn injury, have not previously been discovered. Grass carp bile induces acute renal failure in human beings and presents a special problem local to Taiwan. A partially purified bile salt preparation from the grass carp bile, was studied and found to induce diuresis, haemolysis and drastic falls in blood pressure and cardiac output. A hypothesis is proposed concerning the mechanism by which the bile salts induce renal failure.

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