Studies on the mechanism of sodium excretion during drug-induced vasodilatation in the dog.

The administration of vasodilating agents such as bradykinin and acetylcholine cause an increase in urinary sodium excretion. Yet the mechanisms involved in this natriuretic effect are not clear. Recent studies with another renal vasodilator, secretin have shown this drug also causes a profound increase in renal blood flow but without major changes in sodium excretion. To attempt to delineate the basis of this difference in sodium excretion with these drugs, the renal functional effects of secretin and bradykinin were compared at an equivalent vasodilating dose. Bradykinin increased renal blood flow from 222 to 342 ml/min, urine volume from 0.2 to 1.2 ml/min, and urine sodium excretion from 28 to 115 mueq/min. Urine osmolality fell from 1,230 to 401 mosmol/kg. Secretin caused a comparable increase in renal blood flow (216 to 325 ml/min) while changes in urine flow, sodium excretion, and urine osmolality were significantly less. In further studies papillary plasma flow was estimated using the albumin accumulation technique. Control papillary plasma flow was 29 ml/min per 100 g. Bradykinin increased urinary sodium excretion 108 mueq/min and decreased urinary osmolality from 1,254 to 516 mosmol/kg in association with a rise in papillary plasma flow to 62 ml/min per 100 g. Urine sodium excretion, urinary osmolality, and urine flow rate, as well as papillary plasma flow rate (32 ml/min per 100 g) were unchanged from control when secretin was administered. Studies with acetylcholine were qualitatively similar to those of bradykinin. Renal blood flow increased from 150 to 248 ml/min, urinary sodium excretion increased from 20 to 243 mueq/min, urinary osmolality decreased from 1,237 to 411 mosmol/kg and papillary plasma flow increased from 39 to 52 ml/min per 100 g. It is suggested that the natriuretic effect of some vasodilators is due, at least in part, to alterations in medullary hemodynamics, as evidenced by the increase in papillary plasma flow seen with bradykinin and acetylcholine, but not secretin.

Spontaneous remission of accelerated (malignant) hypertension in renal infarction.

Malignant hypertension occurred in a young man who also was found to have a left renal infarct and higher renal vein renin levels on the left side. His hypertension was controlled with drugs and subsequently treatment with these medications was gradually discontinued over a period of nine months. He remained normotensive when no longer receiving medication, and another intravenous pyelogram demonstrated a persistent cortical defect in the left kidney.

Renal failure with posttransplant renin-angiotensin mediated hypertension.

Ten days after receiving a kidney transplant, severe hypertension and renal failure developed in a patient with a previously functioning graft. Although moderate blood pressure control was achieved with dialysis and antihypertensive medications, the graft did not function well. A trial of sar-ala-angiotensin II (an angiotensin II antagonist) was associated with a dramatic fall in blood pressure. Subsequently, the patient's own two kidneys were removed, the blood pressure fell to normal on the operating table, and within days graft function improved. The possible explanation for the changes in graft function, including angiotensin II-mediated changes of glomerular filtration rate, are discussed.

Role of the autonomic nervous system in the pressor response to calcium in conscious dogs.

The effects of acute hypercalcaemia on arterial pressure and vascular tone have been poorly understood. We analysed the effect of a bolus of calcium chloride (15 mg . kg-1 iv) on arterial pressure, total peripheral resistance, and left ventricular function in 25 conscious dogs studied with or without pharmacological autonomic blockade. Without autonomic blocking drugs, the maximum response to calcium included increases of +139.4 kPa . s-1 (+1046 mmHg . s-1) in maximum rate of change of left ventricular pressure, +2.2 cm3 in stroke volume, +2.6 kPa (+ 19.2 mmHg) in aortic systolic pressure, and +0.6 kPa (+4.4 mmHg) in mean aortic pressure, but total peripheral resistance was unchanged. During beta-adrenergic blockade with propranolol, calcium again increased maximum rate of change of pressure and stroke volume, increased mean aortic pressure (2.2 kPa [+16.5 mmHg]), and increased resistance by 35%. When calcium was given during alpha-adrenergic blockade with phenoxybenzamine or phentolamine, mean aortic pressure did not rise, and resistance fell by 19%. The calcium-induced rise in resistance during beta-adrenergic blockade was abolished by surgical adrenalectomy. We conclude that excess extracellular calcium ion may influence vascular resistance by increasing autonomic nervous system excitation of alpha- and beta-adrenergic vascular receptors. A major mechanism by which the sympathetic nervous system effects occur is through increased release of catecholamines from the adrenal medulla.

Effect of prostaglandins on renal salt and water excretion.

There are several important mechanisms by which renal prostaglandins modulate renal salt and water excretion. The role of endogenous renal prostaglandins in facilitating urinary sodium excretion and the individual nephron segments that are affected by renal prostaglandins are reviewed. The role of the administration of nonsteroidal anti-inflammatory agents on the kidney's ability to excrete salt and water both physiologically and clinically is summarized. The potential role for endogenous prostaglandins to antagonize the effect of antidiuretic hormone and to alter renal water excretion is also described. The clinical consequences of taking nonsteroidal anti-inflammatory drugs in terms of hyperkalemia, sodium retention with associated edema, and possible hyponatremia are all discussed. Although these clinical consequences are quite uncommon statistically, there are certain subsets of patients for whom additional concern is important.

Alport's syndrome associated with macrothrombopathic thrombocytopenia.

The combined occurrence of hereditary nephritis with nerve deafness (Alport's syndrome) and macrothrombocytopathic thrombocytopenia is very rare. The authors have had the opportunity to study such a case in a 20-year-old man who had been followed since birth. The clinical history, renal biopsy, platelet studies, and autopsy findings are presented. The renal pathologic findings are well defined; however, the hemostatic abnormalities and the hearing loss are not well characterized. In this paper, an attept is made to clarify the diverse platelet functional and morphologic abnormalties.

Modulation by food restriction of intracellular calcium signaling in parotid acinar cells of aging Fischer 344 rats.

Previous studies suggest that alpha 1-adrenergic (alpha 1-AR)-induced intracellular calcium ([Ca2+]i) mobilization in rat parotid acinar cells declines with age. In this study, we examined the effects of food restriction on alpha 1-AR and muscarinic-stimulated [Ca2+]i mobilization in parotid acinar cells during aging. [Ca2+]i levels in response to the alpha 1-AR agonist epinephrine and the muscarinic agonist carbachol were evaluated in Fura-2-loaded parotid acinar cells from ad libitum-fed (AL) and food-restricted (FR) Fischer 344 male rats at 4, 6, 14, and 24 months of age. [Ca2+]i responses to epinephrine and carbachol (10 microM) were significantly reduced (48% and 35%, respectively; p < .05) in cells from 24-month-old AL rats as compared to younger AL rats. In contrast, no significant reduction of epinephrine and carbachol responses was observed in 24-month-old FR animals. An age-related increase in basal [Ca2+]i (peak around 14 months; p < .02) was observed in both AL and FR rats. In addition, basal [Ca2+]i was higher in FR than in AL rats at 14 and 24 months of age (p < .02). These studies suggest that FR partially attenuates or delays age-related impairments in alpha 1-AR- and muscarinic-cholinergic signal transduction systems of parotid acinar cells. Basal [Ca2+]i also appears to be altered during aging and by FR.

The natriuretic effect of the organic acid para-aminohippurate.

Infusion of para-aminohippurate (PAH) during renal clearance experiments has been shown to increase urinary sodium excretion (UNAV). In addition, it has recently been suggested that accumulation of PAH and/or related compounds may be responsible for the increased UNAV per nephron in chronic renal failure. Therefore, studies were designed to determine the mechanism for the natriuretic effect of PAH. PAH administration at (0.19 mM per minute) into the dog renal artery led to an average increase in UNAV of 56+/-11 muEq per minute. Mannitol given at this rate (0.19 mM per minute) led to an increase in UNAV of 26+/-10 muEq per minute, which was less than the increase in UNAV with PAH. NA2SO4 given at this (0.19 mEq per minute) or a higher rate (0.60 mEq. per minute) was associated with an increase in UNAV of 53+/-18 and 228+/-38 muEq per minute, respectively. In the PAH and SO4 studies the increase in UPAHV or USO4V was not different from the increase in UNAV. These results suggest that the natriuretic effect of PAH is mainly due to its effect as a nonreabsorbable anion and offer no support for an osmotic effect or a direct effect on active sodium transport.

Prostaglandins may mediate chloride concentration gradient across domes formed by MDCK1 cells.

The MDCK1 and LLC-PK1 cell lines have been used to characterize transepithelial transport in isolated culture. Both can be maintained in continuous culture and form domes that represent fluid actively transported from luminal to contraluminal surface. Fluid in domes from LLC-PK1 cells was isotonic with the culture medium and no Cl gradient between domes and medium was present. Fluid from domes formed by MDCK1 cells was also isotonic with respect to Na and K but there was a persistent Cl concentration gradient. To evaluate prostaglandin (PG) production by these cell lines, the culture medium was analyzed for PGE. LLC-PK1 cells released no measurable PGE; MDCK1 cells regularly released PGE both during basal conditions and after augmentation of PG synthesis by a high Ca concentration in the medium. Qualitatively similar results had previously been found with these cell lines when PG synthesis was augmented with addition of arachidonic acid or Ca ionophore A23187, and PGE or 6-keto-prostaglandin F1 alpha was measured in the medium. To evaluate whether PGs might be responsible for the Cl gradient across MDCK1 cells, indomethacin or meclofenamate was added. There was a marked decrease in the Cl gradient with either agent at 5 h. To evaluate the possibility that PGE2 or PGI2 plays a role in maintaining this Cl gradient, further studies were done in which indomethacin was added to the culture medium to block endogenous PG synthesis, and exogenous PGE2 or PGI2 was added. Although addition of PGE2 was without effect, addition of PGI2 to indomethacin-treated cells maintained the Cl gradient for at least 5 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal effects of nonsteroidal anti-inflammatory agents.

In conclusion, there are a large variety of nonsteroidal anti-inflammatory drugs presently available for clinical use, which on occasion, particularly in human beings with a variety of disease states, can lead to relatively rapid decreases in renal function, particularly glomerular filtration rate. Although it is possible to predict which classes of patients may be more susceptible to this untoward event, even in these groups of patients the incidence of this phenomenon is relatively uncommon and does not preclude the use of these drugs, but rather it suggests that the physician be wary during their administration. Although it is attractive to consider the possibility that these effects are, in part, due to a decrease in endogenous prostaglandins, this issue is still open to active investigation.

Plasma renin activity during exercise in the dog.

Previous workers have suggested that a rise in plasma renin activity (PRA) may mediate some of the hemodynamic changes associated with exercise. To test this hypothesis in nine dogs chronically instrumented for measurement of aortic pressure (catheter) or cardiac output (ascending aorta electromagnetic flow probe) PRA was measured by radioimmunoassay in blood samples drawn before and during running on a level treadmill at 4-8 miles per hour. Exercise caused increases in heart rate from 96 +/- 5 (SE) to 186 +/- 7 beats/min, cardiac output from 2.8 +/- 0.3 to 6.2 +/- 0.6 liters/min, and mean aortic pressure from 115 +/- 5 to 132 +/- 5 mm Hg (P less than 0.01). Mean PRA was 6.6 +/- 0.7 (SE) ng of angiotensin 1/ml per 3 hours before and 7.6 +/- 1.2 ng Ang I during exercise, values that are not different statistically. Propranolol reduced PRA at rest from 8.6 +/- 1.1 to 5.9 +/- 1.1 ng Ang 1 (P less than 0.05), but there was no significant difference between resting and exercise levels, although the increments in heart rate, cardiac output, and mean aortic pressure were reduced. Standing on hindlimbs for 5 minutes did not cause a change in mean aortic pressure or PRA. However, administration of pentolinium reduced mean aortic pressure, and PRA rose from 6.0 +/- 1.1 to 9.8 +/- 1.5 ng Ang I. Exercise, with or without beta-adrenergic blockade, does not cause increased PRA in conscious dogs in which the renin-angiotensin system is normally responsive.

Renal physiology of the prostaglandins and the effects of nonsteroidal anti-inflammatory agents on the kidney.

The prostaglandins are a series of fatty acid products derived from the cellular metabolism of arachidonic acid. The kidney makes prostaglandins and the endogenous renal prostaglandins appear to play a role in the regulation of renal hemodynamics, renal salt and water excretion, and control of the level of activity of the renin-angiotensin system. The administration of nonsteroidal anti-inflammatory drugs blocks cyclooxygenase activity, an early step in the synthesis of prostaglandins. This class of drugs, under certain circumstances, leads to sodium retention, hyperkalemia and several different forms of acute and chronic renal failure. The potential role of altered prostaglandin synthesis in leading to these clinical syndromes is reviewed.

Ammonia production and amino acid metabolism by rat renal papillary epithelial cells in culture.

A significant percentage of excreted ammonium is added to tubular fluid along the medullary collecting duct. However, it is not clear whether this ammonia is produced in the cortex and delivered into the medulla or is produced directly by medullary cells. To address this issue, rat epithelial cells derived from the renal papilla were grown in continuous culture and their ability to generate ammonia was examined. When grown in Dulbecco's modified Eagle's medium with 4 mM glutamine, these cells produced ammonia at a rate of approximately 27 nmol/10(6) cells/h. When these cells were grown in minimum essential medium without glutamine, ammonia production fell to 7 nmol/10(6) cells/ h. Increasing the glutamine concentrations of minimum essential medium to 4 mM increased ammonia production to slightly greater than 30 nmol/10(6) cells/ h. Increasing the media concentration of glutamate, glycine, or asparagine resulted in no significant increase in ammoniagenesis. Analysis of media amino acid concentration revealed that glutamine was the main amino acid consumed while alanine was the predominant amino acid produced. The glutaminase activity of these cells appears to be primarily phosphate-dependent, similar to that observed in vitro in papillary tubules. Alterations of K+ or H+ ion concentration did not alter ammoniagenesis, but addition of 2.5 mM ammonium chloride significantly reduced net ammonia production. It is concluded that rat papillary epithelial cells have the intrinsic ability to utilize glutamine to generate ammonia and alanine. In vivo ammonia produced locally in the medulla may contribute to final urinary ammonium excretion.

Prostaglandin I2 attenuates ischemic acute renal failure in the rat.

We gave prostaglandin I2 (PGI2) (8 ng X kg-1 X min-1 i.v.) for 20 min before, during, and 20 min after clamping of the rat left renal artery for 40 min to evaluate the effect of PGI2 in this model of acute renal failure. Control animals were given glycine buffer (PGI2 diluent). Glomerular filtration rate was estimated by the clearance of inulin 24 h later from each kidney. In group I rats (studied during hydropenia) inulin clearance in the control (right) kidney averaged 1.4 ml/min. Inulin clearance in kidneys exposed to 40 min of ischemia was 0.05 (glycine treated) versus 0.22 (PGI2 treated) ml/min. Although PGI2 offered significant protection in the group I animals, the differences were small and many of the glycine-treated ischemic kidneys were anuric. In the group II studies the same protocol was employed except that 5% body wt volume expansion was done with Ringer solution prior to measurement of inulin clearance. In the group II rats inulin clearance in control (right) kidneys averaged 1.5 ml/min. Inulin clearance after 40 min of renal ischemia was 0.04 ml/min in glycine-treated rats versus 0.90 ml/min in PGI2-treated animals. Histological examination of the group II ischemic kidneys revealed cellular necrosis and cast formation in the S3 segments of the glycine-treated animals and significantly less necrosis and cast formation in the PGI2-treated animals. The degree of necrosis and casts was inversely related to inulin clearance. Accordingly, PGI2 significantly attenuated the fall in inulin clearance measured 24 h after ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

The Spitzer-Weinstein syndrome: one form of type IV renal tubular acidosis and its response to hydrochlorothiazide.

A twelve-year-old girl with persistent hyperkalemia, metabolic acidosis, normal blood pressure and glomerular filtration rate, and short stature (first percentile for height) was studied using metabolic balance techniques. Prior to therapy with hydrochlorothiazide (HCTZ), urinary potassium and acid excretion were low and urine pH was inappropriately high at 5.8. HCTZ (25 mg orally per day) (1 mg/kg) was then started and rapidly corrected her serum electrolytes. The therapy with HCTZ was associated with a diuresis, a decrease in urine pH to 4.8, and concomitant increases in potassium, titratable acid (TA) and ammonium excretion. The increase in TA excretion was explicable, in part, to the decrease in urine pH and, in part, to the considerable increase in phosphate excretion (from 56 to 81 mmol/d). Plasma renin activity and plasma aldosterone increased markedly following HCTZ but urinary prostaglandin E (PGE) excretion was unchanged. These observations suggest that administration of HCTZ in this setting increases hydrogen ion secretion. It is unclear whether this effect is a direct consequence of HCTZ at the level of the tubule or is secondary to some other action of HCTZ. However, it is clear that this effect is not related to an alteration in PGE excretion.

B2-microglobulin and associated amyloidosis presenting as bilateral popliteal tumors.

Chronic hemodialysis has led to the prolongation of life in many patients with end-stage renal disease, but has also allowed for the development of new diseases that are a consequence of this clinical setting. B2-microglobulin accumulation leading to systemic amyloidosis may be the most recent disease in this category. This case report documents the development of bilateral popliteal tumors in a patient undergoing chronic hemodialysis for 9 years. Removal of one of the tumors and pathological examination demonstrated amyloid that was positive for B2-microglobulin by specific antibody testing. This case adds further support to the suggestion that B2-microglobulin amyloidosis in chronic hemodialysis patients is truly a systemic disorder. The development of popliteal tumors, particularly in proximity to joints, in a chronic hemodialysis patient, must include amyloidosis in the differential diagnosis.