Some effects of hypothermia on the circulatory system of the rat
Some effects of hypothermia on the circulatory system of the rat
Hypothermia is the artificial lowering of body temperature below the normal value of 37 ° C. The circulatory responses to hypothermia were found to be similar to those occurring with many kinds of stress; thus some of the changes occurring in hypothermia may be adaptations to promote survival, rather' ,than passive changes imposed by hypothermia. Fbr these studies,' anaesthetised rats were cooled to 25°C by covering th ice, Arterial blood pressure decreased b; 25% in hypothermia, cardiac output' (measured by thermal dilution) was unchanged, plasma volume decreased slightly and haematocrit increased.86_' .The xo,upta~ce method Ibapirstein, iyD5) was shown give reliable blood flow measurements in hypothermic rats. The blood flow.distribution to the organs of the body was altered in hypothermia; some flows increased' (myocardium, brown fat, small intestine, hepatic portal system, lungs), some decreased (kidney, adrenal, spleen, skin, testis, femur) and others remained unchanged (gastrocnemius muscle, abdominal muscle, diaphragm, white fat, most of gut, hepatic arterial system,FIpancreas, thymus).This technique was also used to study the distribution of blood flow to the regions of the kidney. Hypothermia reduced' total kidney bloodflow by 37%o but the flows to the innermost regions of the kidney were, reduced much more than those to the~.outermost regions. These observations help explain some of the changes in kidney function observed in hypothermia.Lost tissue water contents were imaffected by cooling but that of t;-^wn fat increased by 50%. The increased blood flow and water content of brown fat suggest that metabolic heat. production occurs in this tissue during hypothermia.It was shown that rats survive well and.. grow normally after rewaxrsng from 250 C. The cardiovascular adaptations which enable survival are discussed. Sapirstein's method was also used so study the actions of the hormone angiotensin II upon the kidney. The observed blood flow changes could not be correlated with changes in salt and water
University of Southampton
1976
Willson, Rosemary Ann
(1976)
Some effects of hypothermia on the circulatory system of the rat.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Hypothermia is the artificial lowering of body temperature below the normal value of 37 ° C. The circulatory responses to hypothermia were found to be similar to those occurring with many kinds of stress; thus some of the changes occurring in hypothermia may be adaptations to promote survival, rather' ,than passive changes imposed by hypothermia. Fbr these studies,' anaesthetised rats were cooled to 25°C by covering th ice, Arterial blood pressure decreased b; 25% in hypothermia, cardiac output' (measured by thermal dilution) was unchanged, plasma volume decreased slightly and haematocrit increased.86_' .The xo,upta~ce method Ibapirstein, iyD5) was shown give reliable blood flow measurements in hypothermic rats. The blood flow.distribution to the organs of the body was altered in hypothermia; some flows increased' (myocardium, brown fat, small intestine, hepatic portal system, lungs), some decreased (kidney, adrenal, spleen, skin, testis, femur) and others remained unchanged (gastrocnemius muscle, abdominal muscle, diaphragm, white fat, most of gut, hepatic arterial system,FIpancreas, thymus).This technique was also used to study the distribution of blood flow to the regions of the kidney. Hypothermia reduced' total kidney bloodflow by 37%o but the flows to the innermost regions of the kidney were, reduced much more than those to the~.outermost regions. These observations help explain some of the changes in kidney function observed in hypothermia.Lost tissue water contents were imaffected by cooling but that of t;-^wn fat increased by 50%. The increased blood flow and water content of brown fat suggest that metabolic heat. production occurs in this tissue during hypothermia.It was shown that rats survive well and.. grow normally after rewaxrsng from 250 C. The cardiovascular adaptations which enable survival are discussed. Sapirstein's method was also used so study the actions of the hormone angiotensin II upon the kidney. The observed blood flow changes could not be correlated with changes in salt and water
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Published date: 1976
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Local EPrints ID: 467226
URI: http://eprints.soton.ac.uk/id/eprint/467226
PURE UUID: 9ec5532e-234f-4aa6-a995-0004b0010057
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Date deposited: 05 Jul 2022 08:16
Last modified: 05 Jul 2022 08:16
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Author:
Rosemary Ann Willson
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