Localization of alpha 2-adrenoceptor-mediated increase in renal Na+, K+, and water excretion

1987 ◽  
Vol 252 (6) ◽  
pp. F1016-F1021 ◽  
Author(s):  
B. Stanton ◽  
E. Puglisi ◽  
M. Gellai
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Water Transport ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Fractional Excretion ◽  
Urine Osmolality ◽  
Water Excretion ◽  
Arterial Blood ◽  
Adrenoceptor Agonist

Free-flow micropuncture and clearance studies were conducted in male Sprague-Dawley rats to investigate the effects of alpha 2-adrenoceptor stimulation on Na+, K+, and water transport along the nephron. Intravenous infusion of the selective alpha 2-adrenoceptor agonist B-HT 933 at 1 mg X kg-1 X h-1 increased urinary flow rate from 16.2 +/- 3.6 to 84.8 +/- 11.9 microliter/min, fractional excretion of Na+ from 1.36 +/- 0.31 to 3.57 +/- 0.52%, and fractional excretion of K+ from 26.9 +/- 3.0 to 42.3 +/- 2.2%, The diuresis, saluresis, and kaliuresis were not the result of increases in glomerular filtration rate or mean arterial blood pressure. Urine osmolality decreased from 1,126 +/- 177 to 325 +/- 33 mosmol/kg water and in 8 of the 11 animals studied B-HT 933 decreased urine osmolality to hyposmotic levels, suggesting a possible interaction between the alpha 2-adrenoceptor agonist and vasopressin. The alpha 2-adrenoceptor antagonist yohimbine (0.25/mg bolus, iv) inhibited the diuresis, saliuresis, and kaliuresis. In micropuncture studies, B-HT 933 was without effect on single-nephron glomerular filtration rate or on Na+, K+, and water transport along the superficial proximal tubule, loop of Henle, or distal tubule. Thus stimulation of alpha 2-adrenoceptors increases Na+, K+, and water excretion by inhibiting tubule reabsorption of these substances at nephron sites beyond the superficial distal tubule, most likely by the collecting tubule.

Micropuncture study of the superficial nephron of Perognathus penicillatus

1981 ◽  
Vol 241 (6) ◽  
pp. F612-F617
Author(s):  
E. J. Braun ◽  
D. R. Roy ◽  
R. L. Jamison
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Distal Tubule ◽  
Urine Osmolality ◽  
Small Rodent ◽  
Micropuncture Study ◽  
Single Nephron ◽  
Average Body

A micropuncture study of Perognathus penicillatus, a small rodent native to the deserts of the southwestern United States was performed to evaluate the function of the superficial nephron. Data are reported for 12 animals of 17 g average body wt. Mean glomerular filtration rate was 475 +/- 73 microliter X min-1 X g kidney wt-1. Urine osmolality averaged 1,154 +/- 197 mosmol/kg H2O. Single nephron glomerular filtration rate averaged 43 nl X min-1 X g kidney wt-1 in the proximal tubule and 48 in the distal tubule, values that are not significantly different. In terms of the filtered load remaining unreabsorbed at the end of the accessible proximal tubule, the average percentages were 46 water, 48 total solute, 45 sodium, 56 phosphorus, 62 potassium, 71 magnesium, and 54 calcium. The concentrations of potassium and magnesium in fluid samples increased significantly along the proximal tubule. Approximately at the midpoint of the distal tubule, fractional delivery of water, 13.1%, was greater than that for total solute, 10%, or sodium, 7%, indicating that the intervening segment of nephron reabsorbed solute and sodium in excess of water. The function of the superficial nephron resembles that of species previously investigated except for potassium reabsorption in the proximal convoluted tubule.

Meclofenamate and urine concentration with and without exposure of the renal papilla

1981 ◽  
Vol 240 (5) ◽  
pp. F423-F429 ◽  
Author(s):  
R. J. Roman ◽  
C. Lechene
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Urine Osmolality ◽  
Urine Concentration ◽  
Prostaglandin Synthesis ◽  
Urine Flow ◽  
Renal Papilla ◽  
Arterial Blood ◽  
Pelvic Urine

The recent finding that inhibitors of prostaglandin synthesis prevent the fall in urine concentration produced by papillary exposure challenges the hypothesis that contact between the pelvic urine and papilla is essential to the renal concentrating process. The present study examines the change in urine osmolality produced by exposure of the renal papilla in rats given meclofenamate. In control animals urine osmolality(Uosmol) decreased 57% after 2 h of exposure of the renal papilla. In rats given meclofenamate 4 mg/kg urine osmolality increased 16%, urine flow decreased 30%, and glomerular filtration rate was unchanged in the nonexposed kidney. Meclofenamate, however, did not alter the decrease in Uosmol seen in the kidney with the exposed papilla. Meclofenamate 10 mg/kg was also ineffective in preventing the fall in urine osmolality produced by papillary exposure, although this higher dose decreased glomerular filtration rate and arterial blood pressure. These results are consistent with the finding that pelvic urine urea is important to the urinary concentrating process and with the hypothesis that urine osmolality falls after papillary exposure because contact between pelvic urine and papilla is interrupted.

Cisplatin nephrotoxicity in rats: defect in papillary hypertonicity

1981 ◽  
Vol 241 (2) ◽  
pp. F175-F185 ◽  
Author(s):  
R. Safirstein ◽  
P. Miller ◽  
S. Dikman ◽  
N. Lyman ◽  
C. Shapiro
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Collecting Duct ◽  
Urine Volume ◽  
Distal Tubule ◽  
Urine Osmolality ◽  
Solute Content ◽  
Cisplatin Nephrotoxicity

We examined the effects of cisplatin (5 mg/kg BW) on renal function in rats. Three days after administration of cisplatin whole kidney clearance of inulin fell and 24-h urine volume increased. Maximal urine osmolality and papillary solute content were reduced. Superficial nephron glomerular filtration rate measured along the proximal tubule, where no leak of inulin could be demonstrated, was reduced in cisplatin-treated animals. Differences between superficial nephron glomerular filtration rate determined in proximal and distal tubules were greater in cisplatin-treated rats than in control rats. Neither a change in fluid or sodium movement along superficial nephrons nor a reduced early distal tubule transepithelial sodium gradient explain the polyuria. Urea was reabsorbed from, not added to, the loop fluid in cisplatin-treated animals. Morphologic changes were evident in the S3 segment of the proximal tubule in cisplatin-treated animals but the glomeruli were normal. Polyuria occurred despite diminished glomerular filtration rate in cisplatin nephrotoxicity. The diminished concentration of salt and urea in the papilla as a result of abnormal function of the collecting duct or pars recta portion of the proximal tubule contributed to the defect in concentrating ability.

Abstract 386: A Novel Aquaretic and Glomerular Filtration Rate Enhancing Peptide Without Vascular Vasodilatory Actions in Experimental CHF.

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Horng H Chen ◽  
ShuChong Pan ◽  
John C Burnett ◽  
Robert D Simari
Keyword(s):  
Blood Pressure ◽  
Amino Acids ◽  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Urinary Sodium Excretion ◽  
Sodium Concentration ◽  
Water Excretion ◽  
Arterial Blood ◽  
Change In Mean

BACKGROUND: BNP is a cardiac peptide with vasodilatory, natriuretic and diuretic properties. Recent studies have suggested that its vasodilatory hypotensive properties may limit the renal actions of BNP, especially in patients with borderline low blood pressure. We have recently identified an alternatively spliced transcript for BNP (ASBNP) that includes a unique and distinct longer carboxyl-terminus consisting of 34 amino acids. Based upon preliminary studies, we generated a truncated form (ASBNP2.1) that contains the first 16 amino acids of the C-terminal of ASBNP. METHODS: We determined the cardiorenal and humoral actions of intravenous infusion of ASBNP2.1 at 2 pmol/Kg/min, 10 pmol/Kg/min and 100 pmol/Kg /min in 10 dogs with rapid ventricular pacing induced overt CHF (240 bpm for 10 days). * p<0.05 RESULTS: IV infusion of ASBNP 2.1 increased aquaresis (from 0.19±0.04 to 0.32±0.07, 0.46±0.11 and 0.39±0.09 ml/min*) without a significant change in urinary sodium excretion. Importantly, ASBNP 2.1 enhanced glomerular filtration rate (GFR), from 31±4 to 47±8, 69±10 and 56±9 ml/min*. These renal actions were associated with increases in urinary BNP*, ANP* and cGMP* excretion. BNP 2.1 did not have any systemic vasodilatory action resulting in no change in mean arterial blood pressure or cardiac-filling pressures even at the highest dose. There was not change in serum sodium concentration. CONCLUSION: We report for the first time that this novel peptide based upon ASBNP has potent aquaretic and GFR enhancing actions without the vasodilatory hypotensive properties in an experimental model of overt CHF. The lack of vasodilatation but with renal actions also suggest that the C-terminus plays a key role in the vascular actions of this peptide offering new insights into vascular-renal structure function of BNP and related peptides. This renal specific peptide may have potential therapeutic benefit in states of renal dysfunction with volume overload to enhance GFR and water excretion without the detrimental side effect of hypotension.

Effects of late pregnancy and early lactation on renal urea handling in Corriedale ewes

1998 ◽  
Vol 130 (2) ◽  
pp. 213-216 ◽  
Author(s):  
B. B. NDIBUALONJI ◽  
M.-N. RODRIGUEZ ◽  
D. DEHARENG ◽  
A. CIRIO ◽  
J.-M. GODEAU
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Late Pregnancy ◽  
Fractional Excretion ◽  
Urine Osmolality ◽  
Early Lactation ◽  
Plasma Urea

The aim of the study was to investigate the changes in renal function in late pregnant and early lactating Corriedale ewes. Compared with the non-productive state, plasma urea concentration was increased by 67% during pregnancy, whereas it decreased by 36% during lactation. Urine flow, urea clearance, renal plasma flow and glomerular filtration rate were significantly reduced (P<0·05) during both late pregnancy and early lactation. Filtered load of urea and the amount of urea eliminated were significantly reduced (P<0·05) only in lactating ewes. No changes were noted in the fractional excretion of urea, the filtration fraction and the urine osmolality during both late pregnancy and early lactation. It was concluded that, as in other breeds, Corriedale ewes can adapt to increased nitrogen requirements during late pregnancy, and especially during early lactation, by increasing the renal conservation of urea. Unlike other breeds, however, Corriedale ewes restrict the urine urea losses mainly by reducing renal plasma flow and glomerular filtration rate, without any modification of the tubular reabsorption of urea during both late pregnancy and early lactation.

Angiotensin-mediated alterations in nephron function in Goldblatt hypertensive rats

1982 ◽  
Vol 243 (6) ◽  
pp. F553-F560 ◽  
Author(s):  
W. C. Huang ◽  
D. W. Ploth ◽  
L. G. Navar
Keyword(s):  
Glomerular Filtration Rate ◽  
Angiotensin Ii ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Enzyme Inhibitor ◽  
Distal Tubule ◽  
Hypertensive Rats ◽  
Arterial Blood ◽  
Nephron Segment ◽  
Single Nephron

The present study was performed to evaluate superficial nephron responses of the nonclipped kidney to angiotensin I converting enzyme inhibitor (CEI) (SQ 20,881, 3 mg . kg-1 . h-1) in two-kidney, one-clip Goldblatt hypertensive (GH) rats. Late proximal and early distal tubule collections were obtained before and during CEI. Significant increases in glomerular filtration rate, urine flow, sodium excretion, proximal and distal tubule flow rates, and single nephron glomerular filtration rate (from 24.6 +/- 1.7 to 27.5 +/- 1.6 nl/min) occurred despite reductions in arterial blood pressure (from 160 +/- 5 to 137 +/- 6 mmHg) during CEI. Proximal tubule absolute and fractional reabsorption of fluid, chloride, and total solute decreased significantly. In the nephron segment between the two collection sites, there were increases in absolute but decreases in fractional reabsorption. At the distal tubule level, fractional reabsorption but not absolute reabsorption decreased significantly. Proximal and distal tubule hydrostatic pressures increased significantly while peritubular capillary pressure decreased slightly. Responses following inhibition of angiotensin II formation suggest that there exists an angiotensin II-mediated enhancement in tubular reabsorption in the nonclipped kidney of Goldblatt hypertensive rats.

The effect of vasopressin and oxytocin on glomerular filtration rate in the conscious rat: contribution to the natriuretic response

1994 ◽  
Vol 141 (1) ◽  
pp. 59-67 ◽  
Author(s):  
M L Forsling ◽  
J M Judah ◽  
R J Windle
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Plasma Concentrations ◽  
Fractional Excretion ◽  
Conscious Rat ◽  
Arterial Blood ◽  
Fractional Excretion Of Sodium ◽  
Dose Dependent ◽  
Higher Doses

Abstract Urine flow, sodium excretion, mean arterial blood pressure and glomerular filtration rate (GFR) were detennined in the conscious unrestrained rat infused with hypotonic saline. The effects of vasopressin infused at 24 and 160 pmol/min and oxytocin infused at 30 and 200 pmol/min were determined. The lower doses of each hormone gave plasma concentrations within the physiological range whereas the higher doses produced plasma concentrations equivalent to those seen following dehydration. Vasopressin produced dose-dependent antidiuretic and natriuretic responses. Hormone infused at both rates increased the clearance of sodium, but only the higher dose caused a significant increase in GFR. Fractional excretion of sodium was significantly elevated by both doses. Oxytocin produced dose-dependent diuretic and natriuretic responses. Again both rates of infusion increased the clearance of sodium, but only the higher dose caused a significant increase in GFR. The lower dose caused a significant increase in the fractional excretion of sodium. It appears, therefore, that increases in GFR may have a role in the natriuretic response to both hormones. However, this response can also be seen when GFR remains unchanged. This fact, together with the observed increases in the fractional excretion of sodium, indicates that these hormones have additional tubular actions. Journal of Endocrinology (1994) 141, 59–67

Sodium and Water Excretion in Nephrotic Patients: Effects of Changes in Renal Haemodynamics

1990 ◽  
Vol 79 (2) ◽  
pp. 123-129 ◽  
Author(s):  
Michael Allon ◽  
Charles B. Pasque ◽  
Mariano Rodriguez
Keyword(s):  
Glomerular Filtration Rate ◽  
Glomerular Filtration ◽  
Plasma Flow ◽  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Urine Volume ◽  
Sodium Reabsorption ◽  
Plasma Volume Expansion ◽  
Water Excretion ◽  
Significant Change

1. Eight nephrotic patients were studied in order to evaluate the effects of acute changes in renal plasma flow and glomerular filtration rate on renal solute and water handling, in the absence of plasma volume expansion. 2. The subjects were studied first after the administration of captopril, a manoeuvre that increased renal plasma flow without a significant change in glomerular filtration rate, and a second time after receiving combined therapy with captopril and ibuprofen, a manoeuvre that decreased glomerular filtration rate without a significant change in renal plasma flow. 3. After captopril therapy, despite the increase in renal plasma flow, there was no significant change in proximal sodium reabsorption (as estimated from fractional lithium reabsorption), urine volume or urine osmolality. 4. The decrease in glomerular filtration rate observed after the administration of captopril plus ibuprofen was associated with decreases in fractional excretion of sodium and urine volume, and an increase in urine osmolality. The changes in these parameters of tubular function were proportionate to the changes in glomerular filtration rate. Fractional proximal sodium reabsorption increased substantially. 5. These observations suggest that, in the absence of plasma volume expansion, an increase in renal plasma flow does not increase sodium or water excretion by the nephrotic kidney. Moreover, during acute decreases in glomerular filtration rate, glomerulotubular balance appears to be disrupted, resulting in disproportionately high rates of proximal tubule sodium reabsorption.

Effects of blood pH changes on potassium excretion in the dog

1962 ◽  
Vol 202 (4) ◽  
pp. 768-772 ◽  
Author(s):  
Charles Toussaint ◽  
Pierre Vereerstraeten
Keyword(s):  
Glomerular Filtration Rate ◽  
Proximal Tubule ◽  
Glomerular Filtration ◽  
Filtration Rate ◽  
Excretion Rate ◽  
Distal Tubule ◽  
Potassium Excretion ◽  
Ph Changes ◽  
Blood Ph ◽  
Ph Level

K+ excretion rate was measured at normal as well as at rising plasma K+ concentration in intact, in K-depleted, and in acetazolamide-treated dogs submitted to acute blood pH changes. The results indicate that, for any given value of glomerular filtration rate, K+ excretion rate is determined by at least three factors: 1) plasma K+ concentration, 2) blood pH level, and 3) presumably, the H+ gradient across the luminal border of the distal tubule. The data further suggest that most of the filtered K+ is reabsorbed by the proximal tubule, even in conditions of high filtered loads.

Intraruminal rehydration of ovine fetuses

1991 ◽  
Vol 261 (6) ◽  
pp. R1381-R1387
Author(s):  
M. G. Ross ◽  
D. J. Sherman ◽  
M. G. Ervin ◽  
L. Day
Keyword(s):  
Blood Pressure ◽  
Glomerular Filtration Rate ◽  
Filtration Rate ◽  
Plasma Osmolality ◽  
Urine Osmolality ◽  
Distilled Water ◽  
Intravascular Volume ◽  
Fetal Plasma ◽  
Arterial Blood ◽  
Arterial Po2

During oral rehydration of adult mammals, oropharyngeal stimulation, the act of swallowing, and/or gastric factors contribute to a rapid decrease in plasma arginine vasopressin (AVP) that precedes plasma osmolality changes. To determine whether similar mechanisms are present in the developing fetus, six chronically prepared ovine fetuses were rehydrated with intraruminal (IR) distilled water infusions (1 ml.kg-1.min-1 for 60 min) after 43 +/- 3 h of maternal water deprivation. In response to maternal dehydration, significant increases were noted in maternal and fetal mean plasma osmolalities, sodium and AVP concentrations, and fetal urine osmolality. As estimated by hematocrit, fetal intravascular volume decreased by 11%. Fetal rehydration via IR distilled water infusion evoked a significant decrease in fetal plasma osmolality but no change in urine osmolality. Unexpectedly, fetal arterial blood pressure increased and arterial PO2 decreased while fetal hematocrit indicated a further 7% decrease in intravascular volume after the IR infusion. There was a nonsignificant trend toward increased fetal glomerular filtration rate, urine volume, and plasma AVP concentrations. Identical IR water infusions to five euhydrated fetuses resulted in significant decreases in fetal plasma osmolality and increases in glomerular filtration rate, urine flow, and osmolar excretion. The euhydrated fetuses also exhibited significant increases in mean arterial blood pressure and hematocrit and decreased fetal arterial PO2. These results indicate that IR water does not suppress AVP secretion in the dehydrated ovine fetus. Rather, both euhydrated and dehydrated fetuses exhibit an idiosyncratic vasoconstrictive response to IR water.

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