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Full-Text Articles in Medicine and Health Sciences
Exaggerated Natriuretic Response Of Brattleboro Rats To Extracellular Volume Expansion, Susan C. Opava-Stitzer, Emma Fernandez-Repollet, Carmen Rodriguez-Sargent, Jose L. Cangiano, Manuel Martinez-Maldonado
Exaggerated Natriuretic Response Of Brattleboro Rats To Extracellular Volume Expansion, Susan C. Opava-Stitzer, Emma Fernandez-Repollet, Carmen Rodriguez-Sargent, Jose L. Cangiano, Manuel Martinez-Maldonado
Susan C. Opava-Stitzer
A state of chronic dehydration with reduced plasma volume, decreased blood pressure, and increased plasma renin activity (PRA) has been demonstrated in rats with hereditary hypothalamic diabetes insipidus (DI) rats. In this situation decreased renal perfusion and glomerular filtration rate might result in sodium retention. On the other hand, the DI rat also suffers from mineralocorticoid deficiency which might result in salt wasting. In addition it has recently been shown that in contrast to normal rats, there are no differences between superficial cortical and juxtamedullary nephrons of the DI rat with respect to single nephron filtration rate, glomerular volume, and …
Effect Of Potassium On Plasma Renin Concentration In The Presence And Absence Of Adh (Brattleboro Rat Model), Emma Fernandez-Repollet, Susan C. Opava-Stitzer, Manuel Martinez-Maldonado
Effect Of Potassium On Plasma Renin Concentration In The Presence And Absence Of Adh (Brattleboro Rat Model), Emma Fernandez-Repollet, Susan C. Opava-Stitzer, Manuel Martinez-Maldonado
Susan C. Opava-Stitzer
Rats with hereditary hypothalamic diabetes insipidus (so-called DI rats) have elevated plasma renin levels. Although the mechanism responsible for this condition has not be elucidated, it seems reasonable to postulate that the absence of ADH and/or the hypokalemia previously reported in these rats might contribute to the elevation of plasma renin concentration (PRC). Evidence in favor of this hypothesis emerges from studies in which both ADH and potassium have been shown to inhibit renin release. In an attempt to examine the relative roles of ADH and potassium in the regulation of renin secretion, PRC was measured in DI rats maintained …
Effect Of Lithium And Antidiuretic Hormone On Plasma Renin Concentration In Diabetes Insipidus Rats (Brattleboro Rat Model), Susan C. Opava-Stitzer
Effect Of Lithium And Antidiuretic Hormone On Plasma Renin Concentration In Diabetes Insipidus Rats (Brattleboro Rat Model), Susan C. Opava-Stitzer
Susan C. Opava-Stitzer
Antidiuretic horomone (ADH) is known to inhibit renin secretion in many species, but the mechanism of this inhibition and its importance in the control of renin secretion are unknown.
Evidence For Baroreceptor Control Of Renin Release, Paul C. Churchill, Richard L. Malvin, Susan C. Opava-Stitzer
Evidence For Baroreceptor Control Of Renin Release, Paul C. Churchill, Richard L. Malvin, Susan C. Opava-Stitzer
Susan C. Opava-Stitzer
Arterial plasma renin activity (PRA) was measured using radioimmunoassay techniques in pentobarbital-anesthetized dogs. Acute saline loading (40-60ml 150mm NaCl/kg body weight, or 20ml 300mm NaCl/kg body weight, i.v.) reduced PRA from control level in 7 dogs. Despite continued increases in filtered and excreted masses of Na, subsequent partial aortic clamping increased PRA in proportion to the degree of reduction in renal perfusion pressure. In 6 other dogs aortic clamping super-imposed on total ureteral occlusion led to changes in PRA which were inversely associated with renal perfusion pressure. These results suggest a controlling mechanism for renin secretion sensitive to some hemodynamic …
Urine Concentration And Dilution In The Rat: Contribution Of Papillary Structures During High Rates Of Urine Flow, Manuel Martínez-Maldonado, Susan C. Opava-Stitzer
Urine Concentration And Dilution In The Rat: Contribution Of Papillary Structures During High Rates Of Urine Flow, Manuel Martínez-Maldonado, Susan C. Opava-Stitzer
Susan C. Opava-Stitzer
To examine the contribution of papillary structures to the overall process of urine dilution and concentration at high rates of flow, studies were performed in unilaterally papillectomized kidneys (PX). Comparison of kidney weights in sham-operated and PX rats revealed a significant reduction in total weight of the latter. Papillary length removed was 3045 ± 423 μm. GFR was reduced by 24% and 45% in sham and PX kidneys when compared to their contralateral controls. Under hydropenic conditions, maximal urine concentrating ability (Umax) was comparable in control and sham kidneys but was 59% less in PX kidneys. Fractional sodium excretion during …
Role Of Water Balance In The Enhanced Potassium Excretion And Hypokalaemia Of Rats With Diabetes Insipidus, Emma Fernandez-Repollet, Manuel Martínez-Maldonado, Susan C. Opava-Stitzer
Role Of Water Balance In The Enhanced Potassium Excretion And Hypokalaemia Of Rats With Diabetes Insipidus, Emma Fernandez-Repollet, Manuel Martínez-Maldonado, Susan C. Opava-Stitzer
Susan C. Opava-Stitzer
1. The role of water balance in the hypokalaemia of rats with diabetes insipidus (DI rats) was studied. 2. After a 3-day balance study DI rats had a lower muscle potassium content, and plasma [K+], and the urinary excretion of potassium in response to oral KCl loading was reduced when compared to normal rats. The hypokalaemia was found to be associated with elevated concentrations of potassium in renal medulla and papilla when compared to values in normal Long-Evans rats. 3. During a 9-day balance study urinary potassium excretion was higher than that of normal rats on days 1-3, but not …
Pathophysiology Of Clinical Disorders Of Urine Concentration And Dilution, Manuel Martínez-Maldonado, Susan C. Opava-Stitzer
Pathophysiology Of Clinical Disorders Of Urine Concentration And Dilution, Manuel Martínez-Maldonado, Susan C. Opava-Stitzer
Susan C. Opava-Stitzer
A defect in the ability to concentrate or dilute the urine can be easily recognized by the maximum or minimum urine concentration the patient is able to achieve. Maximum concentrating ability (Umax) is determined by the urine osmolality reached after a fixed period of dehydration and maximal diluting ability (Umin) by the minimum osmolality of the urine after the oral ingestion of a fixed water-load. These indices, however, do not allow an understanding of the pathophysiological alterations leading to the presence of the defect.