Head-down tilt and restraint on renal function and glomerular dynamics in the rat

1987 ◽  
Vol 63 (2) ◽  
pp. 505-513 ◽  
Author(s):  
B. J. Tucker ◽  
C. A. Mundy ◽  
M. G. Ziegler ◽  
C. Baylis ◽  
R. C. Blantz
Keyword(s):  
Renal Function ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Extracellular Volume ◽  
Extracellular Fluid ◽  
Conscious Rats ◽  
Single Nephron ◽  
Volume Measurements ◽  
Renal Micropuncture ◽  
Glomerular Ultrafiltration

A model utilizing 25 degree head-down tilt (HDT) and incorporated with chronic catheterization and renal micropuncture techniques in rats was employed to study alterations in renal function induced by HDT. Renal function and extracellular volume measurements were performed after 24 h, 4 days, and 7 days of HDT in conscious rats and compared with their own control measurements and to nontilted but similarly restrained rats. After 24 h HDT, glomerular filtration rate (GFR) increased 19 +/- 8% and renal plasma flow (RPF) increased 18 +/- 8% with increases in urine flow rate, Na+, and K+ excretion in conscious rats. These increases after 24 h were associated with an increase in extracellular volume of 16 +/- 3% (P less than 0.01). In the nontilted controls, there was a decrease in extracellular volume after 24 h of suspension. After 7 days of HDT, GFR was decreased by 7 +/- 1% (P less than 0.01), but RPF and extracellular fluid volume were not different from control values. However, RPF and GFR increased in the nontilted rats after 7 days. After 7 days of HDT renal micropuncture studies demonstrated that single-nephron filtration rate was also decreased from 43 +/- 2 to 31 +/- 3 nl/min (P less than 0.05) due solely to reductions in the glomerular ultrafiltration coefficient (0.11 +/- 0.01 to 0.07 +/- 0.01 nl.s-1 X mmHg-1, P less than 0.05). There was a dissociation between GFR and water and Na+ excretion at days 4 and 7 of HDT not observed in the nontilt restraint controls.

Single nephron function during prolactin-induced pseudopregnancy in the rat

1985 ◽  
Vol 107 (1) ◽  
pp. 127-131 ◽  
Author(s):  
J. Walker ◽  
H. O. Garland
Keyword(s):  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Filtration Rate ◽  
Treated Group ◽  
Female Rats ◽  
Fluid Reabsorption ◽  
Single Nephron ◽  
Renal Changes ◽  
Proximal Tubular ◽  
Renal Micropuncture

ABSTRACT Whole kidney and renal micropuncture techniques were used to investigate the effects of chronic prolactin treatment on kidney function in anaesthetized female rats. At the whole kidney level, glomerular filtration rate (GFR) and fluid reabsorption were both significantly (P<0·02) increased in the hormone-treated group. At the single nephron level, GFR and proximal fluid reabsorption were also increased (P<0·05) by prolactin treatment. Fractional reabsorption was also enhanced at the proximal tubular level in hormone-treated animals. Such changes in renal function are similar to those seen in rat pregnancy and cervically stimulated pseudopregnancy. Since circulating prolactin concentrations are increased in both reproductive states, the hormone may play an important role in establishing the characteristic renal changes seen therein. J. Endocr. (1985) 107, 127–131

Glomerular ultrafiltration in the pseudopregnant rat

1982 ◽  
Vol 243 (3) ◽  
pp. F300-F305 ◽  
Author(s):  
C. Baylis
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Flow Rate ◽  
Plasma Volume ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Plasma Volume Expansion ◽  
Single Nephron ◽  
Glomerular Ultrafiltration

Whole kidney and single nephron indices of glomerular ultrafiltration were measured by clearance and micropuncture techniques in anesthetized virgin, 9-day pregnant, and 9-day pseudopregnant Munich-Wistar rats. Whole kidney glomerular filtration rate (GFR) and single nephron glomerular filtration rate (SNGFR) were elevated in pregnant and pseudopregnant rats compared with virgins (0.78 +/- 0.05, 0.75 +/- 0.06 vs. 0.57 +/- 0.03 ml/min, P less than 0.005 and P less than 0.001; 32.1 +/- 2.5, 30.0 +/- 2.8 vs. 22.1 +/- 2.0 nl/min, P less than 0.01 and P less than 0.05, respectively). Total renal plasma flow rate (RPF) and single glomerular plasma flow rate (QA) were also increased in pregnant and pseudopregnant rats compared to virgins (3.05 +/- 0.19, 2.90 +2- 0.24 vs. 2.28 +/- 0.21 ml/min, P less than 0.01 and P less than 0.05; 109.0 +/- 15.8, 100.4 +/- 12.8 vs. 68.0 +/- 6.9 nl/min, both P less thn 0.05). There was little difference in the other determinants of ultrafiltration among the three groups. Plasma volume was measured in separate experiments and was higher in pregnant and pseudopregnant rats compared with virgins (9.4 +/- 0.2, 9.8 +/- 0.4 vs. 8.4 +/- 0.3 ml, P less than 0.01 and P less than 0.05, respectively). The gestational increase in GFR in the rat occurs as the result of increased RPF, which is due to both plasma volume expansion and renal vasodilation. Since the changes in renal hemodynamics seen in pseudopregnancy were almost identical to those occurring in pregnant rats, the early stimulus to increased GFR must be maternal and not fetoplacental in origin.

EXTRACELLULAR FLUID VOLUME AND RENAL FUNCTION IN PITUITARY INSUFFICIENCY AND ACROMEGALY

1964 ◽  
Vol 46 (1) ◽  
pp. 80-88 ◽  
Author(s):  
Thomas Falkheden ◽  
Björn Sjögren
Keyword(s):  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Extracellular Fluid ◽  
Normal Subjects ◽  
Volume Of Distribution ◽  
Pituitary Insufficiency ◽  
Extracellular Water ◽  
Renal Clearances

ABSTRACT Measurement of the volume of extracellular water (ECW) was performed simultaneously with determinations of glomerular filtration rate (GFR) and renal plasma flow (RPF) in 12 hypophysectomized patients (five cases of metastatic mammary carcinoma and seven diabetic subjects) and in 13 cases of acromegaly. Thirteen normal subjects served as controls. ECW was estimated from the volume of distribution of inulin, GFR and RPF from the renal clearances of inulin and para-aminohippurate, respectively. In the acromegalic group, an increased GFR and RPF was found together with an increased ECW, confirming earlier observations. In the hypophysectomized patients (who were all on cortisone replacement therapy), GFR and RPF were markedly decreased. However, the reduction in GFR and RPF was not associated with any significant changes in ECW.

INTRACELLULAR COMPOSITION AND HOMEOSTATIC MECHANISMS IN SEVERE CHRONIC INFANTILE MALNUTRITION

PEDIATRICS ◽  
1957 ◽  
Vol 20 (2) ◽  
pp. 303-316
Author(s):  
Gustavo Gordillo ◽  
Raphael A. Soto ◽  
Jack Metcoff ◽  
Elizabeth Lopez ◽  
Luis Garcia Antillon
Keyword(s):  
Renal Function ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Defense Mechanism ◽  
Present Report ◽  
Renal Plasma Flow ◽  
Extracellular Fluid ◽  
Free Water ◽  
Hypertonic Solution ◽  
Renal Tubules

The present report deals with preliminary results on the study of renal function in advanced malnutrition. The glomerular filtration rate (clearance of inulin) and renal plasma flow (clearance of para-aminohippurate) were studied in 10 children with severe chronic malnutrition. Osmolar clearance were also measured in six of these children. In three, with marked hypotonicity despite acute dehydration, the effects of intravenous administration of a load of sodium chloride were studied. A significant reduction in filtration rate and renal plasma flow was encountered, which was most evident during dehydration. A decrease in osmolar clearance and the presence of "free-water" clearance in both non-dehydrated and dehydrated malnourished children suggested suspension of the usual antidiuretic mechanisms for conservation of water; however, the rise in osmolar clearance and reabsorption of osmotically free water following administration of hypertonic saline, indicated that the capacity of the renal tubules to respond to an adequate stimulus was not lost. Administration of an hypertonic solution of saline produced a marked expansion of the volume of extracellular fluid. More than half of this expanded volume resulted from redistribution of intracellular "endogenous" water. Expansion of volume limited rise of osmolality of extracellular fluid in two cases, but failed to do so in the third. A relatively large proportion of the filtered water was excreted during hypotonic dehydration. Filtration rates apparently decreased as the proportion of filtered water excreted became increased. The possibility that reduction in filtration rate constitutes a volume defense mechanism and that the apparent anomalies in renal function represent an adaptation to the cellular hypotonicity of the malnourished subject are discussed.

Clinical Renal Function Testing by External Double Isotope Monitoring Technique

1971 ◽  
Vol 10 (01) ◽  
pp. 16-24
Author(s):  
J. Fog Pedersen ◽  
M. Fog Pedersen ◽  
Paul Madsen
Keyword(s):  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Correlation Coefficients ◽  
Feedback System ◽  
Effective Renal Plasma Flow ◽  
Advantages And Disadvantages

SummaryAn accurate catheter-free technique for clinical determination simultaneouslyof glomerular filtration rate and effective renal plasma flow by means of radioisotopes has been developed. The renal function is estimated by the amount of radioisotopes necessary to maintain a constant concentration in the patient’s blood. The infusion pumps are steered by a feedback system, the pumps being automatically turned on when the radiation measured over the patient’s head falls below a certain preset level and turned off when this level is again readied. 131I-iodopyracet was used for the estimation of effective renal plasma flow and125I-iothalamate estimation of the glomerular filtration rate. These clearances were compared to the conventional bladder clearances and good correlation was found between these two clearance methods (correlation coefficients 0.97 and.90 respectively). The advantages and disadvantages of this new clearance technique are discussed.

RENAL FUNCTION AND KIDNEY SIZE FOLLOWING HYPOPHYSECTOMY IN MAN

1965 ◽  
Vol 48 (3) ◽  
pp. 348-354 ◽  
Author(s):  
Thomas Falkheden ◽  
Ingmar Wickbom
Keyword(s):  
Renal Function ◽  
Diabetic Retinopathy ◽  
Glomerular Filtration Rate ◽  
Plasma Flow ◽  
Mammary Carcinoma ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Kidney Weight ◽  
Kidney Size ◽  
Before And After

ABSTRACT Measurements of glomerular filtration rate (GFR) and renal plasma flow (RPF) were performed in close connection with roentgenographic estimation of kidney size, before and after hypophysectomy, in 10 patients (four cases of metastatic mammary carcinoma, five cases of diabetic retinopathy and one case of acromegaly). Hypophysectomy was regularly followed by a decrease in GFR and RPF. In most cases, a reduction in the roentgenographic kidney size was also observed. However, the changes in the roentgenographic kidney size and calculated kidney weight after hypophysectomy were smaller and occurred at a slower rate than the alterations in GFR and RPF. The results favour the view that, primarily, the decrease in GFR and RPF following hypophysectomy is essentially functional rather than due to a reduced kidney mass.

Dynamics of ascites formation in rats with experimental cirrhosis

1980 ◽  
Vol 238 (5) ◽  
pp. F353-F357 ◽  
Author(s):  
J. M. Lopez-Novoa ◽  
M. A. Rengel ◽  
L. Hernando
Keyword(s):  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Hepatic Cirrhosis ◽  
Renal Plasma Flow ◽  
Sodium Balance ◽  
Partial Removal ◽  
Experimental Cirrhosis ◽  
Ascites Formation

Renal function, sodium balance, and ascites formation were observed during induction in rats of experimental cirrhosis. The same variables were studied after partial removal of the ascites in rats with experimental cirrhosis. Glomerular filtration rate (GFR) and effective renal plasma flow (RPF) did not change during hepatic cirrhosis development. Positive sodium balance significantly higher than that observed in controls preceded the appearance of ascites for a period of about 2 wk. When the ascites was removed, GFR, RPF and positive Na balance did not change if Na intake remained constant. Ascites reformation rate was largely dependent on sodium balance. These data strongly support the "overflow" theory of ascites formation and are difficult to reconcile with the classical "underfilling" theory.

Tubuloglomerular feedback control of distal fluid delivery: effect of extracellular volume

1986 ◽  
Vol 250 (6) ◽  
pp. F1024-F1032 ◽  
Author(s):  
L. C. Moore ◽  
J. Mason
Keyword(s):  
Feedback Loop ◽  
Extracellular Volume ◽  
Extracellular Fluid ◽  
Tubuloglomerular Feedback ◽  
Response Curves ◽  
Fluid Delivery ◽  
Fluid Load ◽  
Single Nephron ◽  
Distal Delivery ◽  
Distal Flow

A closed-feedback loop micropuncture method was used to examine tubuloglomerular feedback (TGF) and the regulation of distal fluid delivery in hydropenic rats (CON), moderately hemorrhaged rats (HEM), and rats given desoxycorticosterone (DOC) and 0.6% saline to drink. Distal delivery and TGF response curves were measured with four samples per nephron: a spontaneous early distal collection, two distal collections during moderate (7.5 nl/min) and saturating (30 nl/min) perturbations in nephron fluid load, and a proximal collection to measure single-nephron glomerular filtration rate (SNGFR) during TGF inhibition. Arterial pressure, predistal volume reabsorption, SNGFR, and early distal flow were significantly higher in DOC than in HEM; the CON group exhibited intermediate values. Except for a greater maximum TGF response in HEM, the normalized TGF responses were similar in all three groups, as was the regulation of distal fluid delivery. However, the TGF onset threshold and the TGF operating point, defined by the spontaneous rates of early distal flow and SNGFR, were reset such that distal fluid delivery and SNGFR were higher in DOC than in HEM, as was renal sodium excretion. The results show that the level around which TGF stabilizes distal fluid delivery is reset when extracellular fluid volume is altered.

scholarly journals Glucagon-like peptide-1 receptors in the kidney: impact on renal autoregulation

2020 ◽  
Vol 318 (2) ◽  
pp. F443-F454 ◽  
Author(s):  
Aleksander Vauvert R. Hviid ◽  
Charlotte M. Sørensen
Keyword(s):  
Type 2 Diabetes ◽  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Kidney Function ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Glucagon Like Peptide ◽  
Glucagon Like Peptide 1 ◽  
Study Participants

Glucagon-like peptide-1 (GLP-1) and strategies based on this blood sugar-reducing and appetite-suppressing hormone are used to treat obesity and type 2 diabetes. However, the GLP-1 receptor (GLP-1R) is also present in the kidney, where it influences renal function. The effect of GLP-1 on the kidney varies between humans and rodents. The effect of GLP-1 on kidney function also seems to vary depending on its concentration and the physiological or pathological state of the kidney. In studies with rodents or humans, acute infusion of pharmacological doses of GLP-1 stimulates natriuresis and diuresis. However, the effect on the renal vasculature is less clear. In rodents, GLP-1 infusion increases renal plasma flow and glomerular filtration rate, suggesting renal vasodilation. In humans, only a subset of the study participants exhibits increased renal plasma flow and glomerular filtration rate. Differential status of kidney function and changes in renal vascular resistance of the preglomerular arterioles may account for the different responses of the human study participants. Because renal function in patients with type 2 diabetes is already at risk or compromised, understanding the effects of GLP-1R activation on kidney function in these patients is particularly important. This review examines the distribution of GLP-1R in the kidney and the effects elicited by GLP-1 or GLP-1R agonists. By integrating results from acute and chronic studies in healthy individuals and patients with type 2 diabetes along with those from rodent studies, we provide insight into how GLP-1R activation affects renal function and autoregulation.

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