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Title:The Renin-Angiotensin System in The Freshwater Turtle Pseudemys Scripta
Author(s):Cipolle, Mark David
Department / Program:Physiology and Biophysics
Discipline:Physiology
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Biology, Animal Physiology
Abstract:Initially, experiments were conducted to verify the existence of an endogenous renin-angiotensin system in this species. It was shown that Pseudemys scripta possess renal renin, renin substrate in the plasma, angiotensin converting enzyme activity, and vascular receptors specific for angiotensin. Kinetic analyses were performed on the turtle renal renin (kidney extract) plus turtle renin substrate (plasma) reaction, and the K(,m) for turtle renin determined. Comparing turtle angiotensin to mammalian {Asp('1), Ile('5), His('9)} angiotensin I on the basis of their biological, immunological, and chromatographic properties indicated that the primary structure of the turtle peptide is most likely different from that of mammalian angiotensin I. It was shown that a significant portion of turtle plasma renin may exist in an inactive form which can be made more active by in vitro acidification to pH 3.3 via dialysis.
Several series of experiments were conducted to examine factors that may play a role in controlling turtle renin release. Unlike in mammals, cumulative hemorrhage had no effect on turtle plasma renin activity in either anesthetized or conscious turtles despite the fact that hemorrhage resulted in decreasing the mean arterial blood pressure to less than half the control value. Also, unlike mammals, intravenous infusion of the beta-adrenergic agonist isoproterenol (2 (mu)g/kg per min for 30 min) had no effect on turtle plasma renin activity. Conversely, infusion of acetylcholine (0.05 mg/kg per min for 30 min) caused plasma renin activity to increase nearly three-fold. The acetylcholine-mediated renin response was not affected by pre-treating the turtles with atropine (1 mg/kg). However, the renin response was not present in turtles pre-treated with the beta-adrenergic antagonist d,1 propanolol (4 mg/kg).
Chronic furosemide administration (three intramuscular doses of 10 mg/kg over 48 hr) had a profound stimulatory effect on renin release concomitant with significant decreases in plasma sodium and potassium levels.
What role the renin-angiotensin system plays in the freshwater turtle remains unsettled. More studies are warranted before we can assign any specific physiological function(s) to the turtle renin-angiotensin system.
Issue Date:1983
Type:Text
Description:233 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983.
URI:http://hdl.handle.net/2142/71421
Other Identifier(s):(UMI)AAI8309928
Date Available in IDEALS:2014-12-16
Date Deposited:1983


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