Joseph Levi

Effect of Parathyroid Hormone on Osmotic Fragility of Human Erythrocytes

The survival of erythrocytes (RBC) is shortened in uremia, and it has been shown that calcium influx into RBC evoked crenation and increased their rigidity. The high blood levels of parathyroid hormone (PTH) may augment entry of calcium into RBC and hence affect their integrity. We examined the effect of PTH on osmotic fragility of human RBC and investigated the mechanisms through which PTH interacts with RBC. Both the amino-terminal (1-34) PTH and the intact (1-84) PTH, but not the carboxy-terminal (53-84) PTH, produced significant increases in osmotic fragility. This effect was abolished by prior inactivation of the hormone. There was a dose-response relationship between both moieties of PTH and the increase in osmotic fragility. This action of PTH required calcium, was mimicked by calcium ionophore, and was partially blocked by verapamil. PTH caused significant influx of (45)Ca into RBC, which was not associated with potassium leak. The hormone did not affect water content of RBC. Scanning electron microscopy revealed that the incubation of RBC with PTH was associated with the appearance of membrane filamentous extensions, which anchor RBC together. Inhibition of glycolytic activity of RBC with NaF or inhibition of Na-K-activated ATPase with ouabain did not abolish the effect of PTH on osmotic fragility. PTH did not stimulate RBC Na-K-activated ATPase or Mg-dependent ATPase but caused marked and significant stimulation of Ca-activated ATPase. The basal activity of the RBC adenylate cyclase was low and PTH produced only a modest stimulation of this enzyme. Both cyclic AMP and dibutyryl cyclic AMP had no effect on osmotic fragility. THE DATA INDICATE THAT: (a) the RBC is a target organ for PTH, (b) the hormone increases osmotic fragility of RBC, and (c) this effect of PTH is due to enhanced calcium entry into RBC. We suggest that the increased calcium influx may affect the spectrin-actin of the cytoskeletal network of the RBC and may alter the stability and integrity of the cell membrane. This action of PTH on the RBC could be, at least in part, responsible for the shortened survival of RBC in uremia, and assign a new role for PTH in the pathogenesis of the anemia of uremia.

Hypocalcemia in magnesium-depleted dogs: Evidence for reduced responsiveness to parathyroid hormone and relative failure of parathyroid gland function

The effect of magnesium depletion on serum calcium and magnesium and on the response to the infusion of parathyroid extract (PTE) was evaluated in nine adult mongrel dogs during a control period, magnesium depletion, and following magnesium repletion. Magnesium depletion was associated with a fall in serum magnesium and calcium, and both returned to normal with magnesium repletion. There was a significant direct correlation between the serum concentration of calcium and magnesium in the magnesium-deficient state. During magnesium depletion, there were significant calcemic and phosphaturic responses to PTE, but these effects were reduced; the impaired responsiveness of the skeleton and the kidney to PTE returned to normal after magnesium repletion. Serum levels of immunoreactive parathyroid hormone, measured in two animals during the control and magnesium depletion state, remained stable during magnesium depletion, despite the hypocalcemia present. These results indicate that both impaired responsiveness of the skeleton to parathyroid hormone and reduced secretion of the hormone in response to hypocalcemia exist in dogs with magnesium depletion. Each of these factors probably contributes to a reduced level of serum calcium in magnesium depletion, and they may compound each other and hence aggravate the degree of hypocalcemia.

Elevated Thrombocyte Calcium Content in Uremia and Its Correction by 1α(OH) Vitamin D Treatment

Intracellular calcium plays an important role in the regulation of platelet function. It has also been demonstrated that platelet functions are impaired in uremia. A rise in intracellular calcium has

Proximal renal tubular acidosis: association with familial normaldosteronemic hyperpotassemia and hypertension.

Further investigation of a family with normaldosteronemic hyperpotassemia and low-renin hypertension showed seven members from three generations, who ranged in age from 4 to 56 years, to be affected. Results of earlier studies had established a normally functioning renin-aldosterone system and normal renal handling of potassium. Constant, albeit mild and asymptomatic, metabolic acidosis in all those affected prompted bicarbonate loading in both the propositus and his brother, which revealed a maximal renal tubular excretory capacity for bicarbonate reabsorption at serum levels of 18 mmole/liter and proved proximal renal tubular acidosis (PRTA). Further, a linear increase in urinary fractional potassium excretion accompanied that of bicarbonate in both, as in normal individuals. Dextrose-insulin infusion in the brother failed to reduce hyperpotassemia. These data support the hypothesis that a generalized cell membrane defect that specifically impedes potassium influx (as opposed to an isolated renal tubular defect) underlies this autosomal dominant disorder.

Unusual case of crescentic glomerulonephritis associated with malignant lymphoma : a case report and review of the literature

Renal lesions in non-Hodgkins lymphoma are rare. Furthermore, to the best of our knowledge, only 5 cases of crescentic glomerulonephritis associated with non-Hodgkins lymphoma have been previously described. We report a case of crescentic glomerulonephritis and renal failure which preceded the diagnosis of non-Hodgkins lymphoma. Following steroid therapy there was a resolution of these histological findings a year later.

Androgen-Associated Hepatoma in a Hemodialysis Patient

A patient on hemodialysis treatment developed hepatocellular carcinoma (HCC) after long-term therapy with androgenic anabolic steroids. The tumor progressed very rapidly, and there was no evidence of regression despite discontinuation of the drug. In view of the evidence of an increased of malignancy in patients with chronic uremia and hemodialysis, and of the higher frequency of HCC correlated to treatment with C17-alkylated anabolic steroids, it is necessary to further evaluate the efficiency of this treatment in the aforementioned group of patients.

The effect of high-dose nifedipine on renal hemodynamics of cyclosporine-treated renal allograft recipients

Cyclosporine has been shown to reduce renal perfusion and to decrease glomerular filtration rate. Experimental studies suggest that nifedipine might reverse this renal vasoconstrictive effect of cyclosporine. We studied renal hemodynamics of 5 cyclosporine-treated renal transplant recipients before and after 2 weeks of therapy with high-dose nifedipine (up to 120 mg/day). Pretreatment GFR and renal plasma flow (RPF) were decreased. Following administration of nifedipine, RPF increased by 18% (P less than 0.01), while GFR did not change. Filtration fraction decreased by 10.5% (P less than 0.01). Mean arterial pressure declined from 111 +/- 5 to 96 +/- 3 mmHg (P less than 0.01). Renal vascular resistance dropped by 25% (P less than 0.01). Calculated postglomerular plasma flow increased by 20.5% (P less than 0.01). Urinary albumin excretion rate was unaffected. Cyclosporine whole blood levels were unchanged. The increase in RPF and in postglomerular plasma flow suggests that high-dose nifedipine might lessen cyclosporine-induced glomerular and interstitial ischemia in renal allograft recipients.

Twenty-four-hour blood pressure monitoring during treatment with extended-release felodipine versus slow-release nifedipine: cross-over study.

The lack of comparative studies of nifedipine and felodipine using 24-h blood pressure (BP) monitoring in the same patients led to the present study evaluating the antihypertensive efficacy and side effects of treatment with slow-release (SR) nifedipine (20 mg twice daily) and extended-release (ER) felodipine (10 mg once daily). In the double-blind study, subjects were randomly assigned to one of two treatment groups: 6 weeks of nifedipine SR (20 mg twice daily) followed by 6 weeks of felodipine (ER) (10 mg once daily with evening matched placebo), or vice versa. Twenty-four-hour ambulatory BP monitoring showed no significant differences in systolic BP (SBP) during the day. There were no significant differences in diastolic BP (DBP) throughout the 24 h, although the frequency of DBP recordings > 90 mm Hg was greater during nifedipine (33.1%) than felodipine (27.75%) treatment. The most common side effects were flushing, palpitations, headaches, and ankle edema; there were no adverse effect on lipid profile or glucose level.

Angiotensin-Converting Enzyme Inhibition and Anaemia in Renal Patients

A 35-year-old renal transplant patient with stable renal function developed an unexplained anaemia. Appropriate investigations proved non-diagnostic. Only when enalapril therapy was stopped did the anaemia reverse and haemoglobin levels returned to pre-treatment levels. An association between angiotensin-converting enzyme inhibitors and anaemia in patients with renal failure is becoming more evident. A literature review of this problem and its possible pathogenesis in patients with renal failure is given.

Biochemical changes associated with the osmotic fragility of young and mature erythrocytes caused by parathyroid hormone in relation to the uremic syndrome.

The effect of parathyroid hormone at concentrations found in uremic patients on erythrocytes (RBC) from newborn and adult rabbits was studied in relation to the fragility pattern in hypotonic salt solutions and the activities of Ca- and Mg-dependent ATPases. Median osmotic fragility of RBC from newborn rabbits was significantly lower than in mature rabbits. Parathyroid hormone (PTH) stimulated to a greater extent the mean osmotic fragility in RBC from newborn rabbits, than in those from adults. Similarly, the hormone stimulated to a much greater extent the Ca-ATPase but not the Mg-ATPase in RBC from the newborn rabbits, in comparison to those from adult rabbits. PTH, which is greatly elevated in the blood of patients with chronic renal failure, may be one cause of the anemia seen in these patients, and its effect, which is mediated by Ca-ATPase activity, is stronger on young RBC. There were significant morphological changes in the young RBC caused by PTH, as seen with scanning electron microscopy.