Studies on rat intestinal fluid absorption in vivo
Studies on rat intestinal fluid absorption in vivo
Studies were undertaken to investigate the effects of changes in extracellular fluid volume upon fluid absorption in the rat jejunum in vivo. The results demonstrate that a reduction in extracellular-fluid ' volume causes an increase in fluid absorption when measured 24 hours later, and conversely, that an increase in extracellular fluid volume results in a decrease in fluid transport. The response to extracellular fluid reduction remains in adrenalectomised animals, but responses both to increases and decreases in extracellular fluid are abolished by prior removal of the kidneys. The jejunum of 24 hour nephrectomised rats responds as normal to intravenous infusions of the hormone angiotensin II and to intraluminal injections of glucose solution, indicating that it is a viable preparation. On the basis of these observations, it was considered that the factor most likely to mediate the response was renin, however measurements of plasma renin activity in rats experiencing an extracellular fluid volume depletion (by haemorrhage) show that there is no increase in levels associated with the increase in fluid transport. In the short-term; 'an increase in plasma' renin activity is observed 30 minutes after a haemorrhage and this coincides with a rise in fluid transport levels. Investigations of the structure-activity requirements of the intestinal angiotensin receptor demonstrate that the receptor involved in stimulation of fluid transport differs from those in pressor and myotropic systems, in that it does not require phenylalanine in position 8. An analogue substituted in this position (sarcosine1, threonine angiotensin II) and an analogue with phenylalanine 8 deleted (1-7 heptapeptide of angiotensin II) both stimulate fluid transport but have no agonist activity on either pressor or myotropic systems. Analogues modified in other positions of the molecule have similar activities on all systems, with the exception of the 1-S pentapeptide of angiotensin II. This stimulates fluid transport but is inactive on pressor and myotropic systems.
University of Southampton
Mariscotti, Sheila Patricia
396587f4-9f03-4f59-882a-d4f78f2a515e
1979
Mariscotti, Sheila Patricia
396587f4-9f03-4f59-882a-d4f78f2a515e
Mariscotti, Sheila Patricia
(1979)
Studies on rat intestinal fluid absorption in vivo.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Studies were undertaken to investigate the effects of changes in extracellular fluid volume upon fluid absorption in the rat jejunum in vivo. The results demonstrate that a reduction in extracellular-fluid ' volume causes an increase in fluid absorption when measured 24 hours later, and conversely, that an increase in extracellular fluid volume results in a decrease in fluid transport. The response to extracellular fluid reduction remains in adrenalectomised animals, but responses both to increases and decreases in extracellular fluid are abolished by prior removal of the kidneys. The jejunum of 24 hour nephrectomised rats responds as normal to intravenous infusions of the hormone angiotensin II and to intraluminal injections of glucose solution, indicating that it is a viable preparation. On the basis of these observations, it was considered that the factor most likely to mediate the response was renin, however measurements of plasma renin activity in rats experiencing an extracellular fluid volume depletion (by haemorrhage) show that there is no increase in levels associated with the increase in fluid transport. In the short-term; 'an increase in plasma' renin activity is observed 30 minutes after a haemorrhage and this coincides with a rise in fluid transport levels. Investigations of the structure-activity requirements of the intestinal angiotensin receptor demonstrate that the receptor involved in stimulation of fluid transport differs from those in pressor and myotropic systems, in that it does not require phenylalanine in position 8. An analogue substituted in this position (sarcosine1, threonine angiotensin II) and an analogue with phenylalanine 8 deleted (1-7 heptapeptide of angiotensin II) both stimulate fluid transport but have no agonist activity on either pressor or myotropic systems. Analogues modified in other positions of the molecule have similar activities on all systems, with the exception of the 1-S pentapeptide of angiotensin II. This stimulates fluid transport but is inactive on pressor and myotropic systems.
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Published date: 1979
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Local EPrints ID: 471210
URI: http://eprints.soton.ac.uk/id/eprint/471210
PURE UUID: 8bd80ac8-7c7b-4485-9685-bd763d9ed4b7
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Date deposited: 31 Oct 2022 18:03
Last modified: 31 Oct 2022 18:03
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Author:
Sheila Patricia Mariscotti
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