Failure to show a correlation between serum parathyroid hormone, nerve conduction velocity and serum lipids in hemodialysis patients

The proposed role of parathyroid hormone as an important agent for the development of certain uremic complications could not be confirmed in studies correlating, in dialysis patients, the nerve conduction velocity and the serum lipids with four different immunochemically defined forms of circulating parathyroid hormone. To a certain extent the data invalidate suggestions which favor parathyroid hormone as a leading uremic toxin.

[Treatment of renal osteopathy with 5,6-trans-25-hydroxycholecalciferol (author's transl)]

The influence of 5,6-trans-25-hydroxycholecalciferol on renal osteopathy was investigated in a total of 132 patients in 26 dialysis centres. Various doses were used, the average being 4000-6000 IU/day. In 32 patients a daily dose of 6000-9000 IU was used. The average individual duration of treatment was 276 days with a maximum of 910 days. Histologically there was an improvement in the renal osteopathy in 55.9% of evaluable cases (n = 34) and in 25.3% there was no deterioration. Radiographically these results were found in 21% and in 70.5% of evaluable cases (n = 105). Serum calcium increased in 46.6% of cases (n = 131), remained the same in 32.8% and decreased in 20.6%. The changes in alkaline phosphatase were similar : it dropped in 42.1% of patients, remained the same in 28.1% and rose in 29.8%. Immunoreactive parathormone which was invariably raised at the beginning of treatment (n = 36), fell in 25.0%, remained the same in 44.4% and rose further in 30.6%. The clinical symptoms of renal osteopathy which had been present in 57 patients improved in 51.0%, remained the same in 46.0% and deteriorated in 3.0%. Signs of intolerance and side effects were rare. Severe hypercalcaemia did not occur.

Chronic hemofiltration. A critical evaluation of a new method for the treatment of blood

The experiences which have been compiled in more than 2400 hemofiltrations confirm that this method represents an alternative way of treating uremic patients. The main advantages of chronic hemofiltration are the comfort of the patient and the ease in handling excess overhydration without extending treatment time, which is less than 3 X 3 hours/week if adequate hemofilters are used. With regard to the improvement of such typical uremic complications as severe hypertension, hypertriglyceridemia or neuropathy, hemofiltration does not seem to be superior to hemodialysis. However, since most hemofiltration patients do not require phosphate binders and, additionally, remarkable amounts of parathyroid hormone are removed during one hemofiltration, it appears possible that hemofiltration might be an important therapeutic alternative for those renal patients who suffer from severe hyperphosphatemia and secondary hyperparathyroidism.

[Investigations on the pharmacokinetics of pentoxifylline in chronic renal failure (authors transl)]

The pharmacokinetical behaviour of 14C-labelled pentoxifylline was investigated in normal volunteers and in patients with different stages of impaired renal function. It was shown that in patients, having a creatinine-clearance of less than 10,0 ml/min., occurs an accumulation of pentoxifylline. This finding leads to the conclusion that in patients with advanced renal failure the daily dose of pentoxifylline should be adjusted to the diminished renal elimination.

The hemofiltration system: variations of the negative pressure

The physical conditions of the hemofiltration process are briefly discussed to describe the applied system that is characterized by a negative pressure pump which is directly attached behing the filter. A schema is presented that shows the characteristics of a fully automatic hemofiltration apparatus that is presently in development.

Parathyroid hormone-, 25-OH-vitamin D-, and digoxin levels in patients treated by chronic hemofiltration

Immunoreactive parathyroid hormone (iPTH) was measured in the serum and filtrate before, during and after hemofiltration. iPTH regularly declines during hemofiltration; one patient, investigated for a longer period, showed a normalization of iPTH serum level with this treatment. The iPTH values found in the hemofiltrate were remarkably high, a finding that could be explained by non-specific effects, by the occurrence of hormone fragments or by an increased secretion rate. At any rate, the results suggest a filtration of parathyroid hormone and/or hormone fragments. On the other hand, it was impossible to detect any 25-OH-vitamin D in the hemofiltrate. Finally, digoxin could be found in the filtrate, but only in very low concentrations.

Clinical aspects of hemofiltration

We report on clinical experiences obtained in 7 uremic patients treated since January 1976 3 times weekly by chronic hemofiltration. The observations which we collected in more than 300 treatments suggest that hemofiltration might be superior to conventional hemodialysis. The main advantages of this treatment are characterized by its better control of hypertension, hyperhydration, and possibly of uremic bone disease. Furthermore, the applied acrylonitrile membrane allows the removal of substances with a molecular weight up to 60,000, similar to the glomerular basement membrane. Additionally, we report on methodological problems, on the compatibility of hemofiltration, and finally on its efficiency for removal of different uremic solutes.

[Immunoreactive parathyroid hormone, 25-hydroxycalciferol and bone histology in renal osteodystrophy (author's transl)]

Immunoreactive parathyroid hormone (iPTH) and 25-hydroxycalciferol (25(OH)D) serum levels were determined in 32 patients with renal osteopathy, they were correlated with the results of bone biopsy and other clinical parameters. iPTH was closely related to bone histology, it did not correspond to serum calcium and alkaline phosphatase, but the correlation to serum phosphate was statistically significant. 25(OH)D levels were not related to the histological findings of osteomalacia or increased bone resorption, while a correlation between the vitamin D metabolite and serum calcium could be observed. Since iPTH and 25(OH)D levels exhibited a significant correlation, an inhibitory effect of 25(OH)D on parathyroid gland function in renal failure was discussed.

[Effect of pentoxyfylline on the organ distribution of 47Ca and on intestinal Ca absorption and secretion in the rat (author's transl)]

The influence of 3,7-dimethyl-1-(5-oxo-hexyl)-xanthine (pentoxyfylline, Trental) on organ distribution of 47Ca and on intestinal Ca absorption and secretion was studied in rats. Oral application of 4 mg/kg bodyweight pentoxifylline was followed after 30 min by a significantly higher accumulation of orally applied 47Ca in the intestinal wall as compared to untreated controls, while in other organs the 47Ca activity was lower than in control animals. When 47Ca was given i.p. and pentoxifylline at the same dose was applied orally 24 h later, there was no difference in organ distribution of 47Ca between treated rats and untreated controls after 30 min. There was likewise no difference in serum Ca concentration. On the other hand, i.v. infusion of 20.8 mg/kg bodyweight pentoxifylline was followed by a significant fall of serum Ca. At the same time, there was a significant reduction of intestinal Ca net absorption, as demonstrated by the intestinal perfusion technique, while Ca net secretion was not influenced. The possible mechanisms causing the pentoxifylline induced reduction of serum Ca concentration are discussed.

Pharmacokinetics of 5,6-trans-25-hydroxycholecalciferol, a synthetic analogue of vitamin D3, in man

Vitamin D analogues of high biological activity are probably useful in the treatment of renal osteodystrophy. The pharmacokinetics of the synthetic compound 5,6-trans-25-hydroxycholecalciferol have been studied in healthy subjects who were of normal vitamin D status. In comparison to natural 25-hydroxy-cholecalciferol, serum levels of the analogue were lower and its half-life in blood after oral or intravenous administration was considerably shorter. In normal subjects no increase of dihydroxylated metabolites in serum was observed within seven days of an intravenous dose.

The effect of Solanum malacoxylon on rachitic bone lesions in the rat

The plant Solanum malacoxylon (S.M.) is known to cause severe soft tissue calcifications in cattle and sheep and has recently become of special interest since it exerts biological actions which resemble those of vitamin D. In order to investigate whether S.M. is capable to improve the rachitic bone changes in vitamin D and phosphate deficient rats, a watery extract of 50, 100 and 200 mg S.M. was fed daily to these animals over a period of 10 days. The width of epiphyseal plates was compared after the time with those of rats treates with 0, 0.225, 0.45, and 0.9 IU of vitamin D3 daily. There was a dose related curative effect of S.M. on the epiphyseal lesions very similar to that of vitamin D3. The hypercalcemic and hyperphosphatemic effect of S.M. was identical to that of vitamin D3. The 25-hydroxy-vitamin D serum levels remained almost undetectable in the S.M. treated rats as well as in the vitamin D3 treated animals.

The metabolism and organ distribution of 5,6-trans-25-hydroxycholecalciferol, an analog of vitamin D-3 in vitamin D-deficient rats

Investigations have been performed on the metabolism and organ distribution of 5,6-trans-25(OD)D-3, which represents an analog of vitamin D-3 being active in uremia. This analog is rapidly metabolized into at least two more metabolites. The main storage organ for this compound seems to be fat, whereas liver and intestinal mucosa showed at 24 hrs the highest concentration of polar metabolites. In contrast to 25(OH)D-3 5,6-trans-25(OH)D-3 is much less absorbed from the intestinal tract, which should be considered if this compound is applied for treatment of uremic bone diseases.