Adsorption of human recombinant erythropoietin on dialysis membranes in vitro.

The adsorptive characteristics of 5 dialysis membranes for recombinant human erythropoietin (EPO) were studied in vitro in a closed circuit system. For 120 min, EPO added with bovine serum was significantly adsorbed by polymethylmethacrylate (PMMA) and polyacrylonitrile (PAN) membranes but not by Cuprophan, ethylene vinyl alcohol (EVAL), or polysulfone (PS) membranes. In addition the EPO adsorptive rate, as well as that of beta 2-microglobulin (beta 2-MG), was greater with a PMMA membrane than with a PAN membrane. EPO was not detected in the ultrafiltrate at 15 min with 5 membranes. These results indicate that EPO was eliminated by membrane adsorption only with some dialysis membranes.

Effect of phosphate depletion on vasopressin secretion and kidney tissue vasopressin concentration in rats.

The effects of chronic phosphate depletion on vasopressin (ADH) secretion and kidney tissue ADH concentration were examined in rats fed on a diet containing 0.26% phosphorus (LP) or 0.99% phosphorus (NP). The concentration of plasma phosphorus (P) fell significantly in the LP rats after a 4-week period on the experimental diet. There was no significant difference between the LP and NP rats as regards their plasma ADH concentrations and kidney tissue ADH concentrations in normal hydration after a 4-week period on the experimental diets. Following hypertonic saline tests, the plasma ADH concentrations increased significantly in the LP and NP rats, but there was no significant difference between the groups. The kidney medulla and papilla ADH concentrations increased significantly with plasma ADH elevations in both groups. Again, no difference could be found in the cortico-medullary ADH concentration gradients between the two groups. These results indicate that chronic hypophosphatemia in phosphate depleted rats may not be related to ADH secretion and the distribution or tissue concentration of ADH in the kidney. Further, our data suggest that a low plasma P does not influence the ability of ADH to bind to kidney receptor in rats.

[Studies on small thyroid carcinoma in dialysis patients with hyperparathyroidism].

For twenty long-term hemodialysis patients with medically uncontrolled hyperparathyroidism, subtotal parathyroidectomy (PTX) was performed and histological examination was done for 17 out of them, suspected of thyroid disease from operative findings. Thyroid carcinomas were found in 5 out of 17 patients by biopsied specimens of thyroids. Histological findings of carcinomas were follicular (2 cases) and papillary types (3 cases). In all cases, carcinomas were in occult state and the sizes of carcinomas of 4 cases were small being a diameter less than 10 mm. Among others, findings of follicular adenoma (2 cases) and chronic thyroiditis (1 case) were obtained. The incidence rate of thyroid carcinoma in this report seemed to be rather high as the incidence diagnosed from biopsied specimen at operation. Several factors such as immunological incompetence accompanied by renal failure, metabolic abnormalities of cells induced by parathyroid dysfunction and accelerated aging are considered to be involved as a cause of increased incidence of thyroid carcinoma in hemodialysis patients with hyperparathyroidism.

Effect of 1,25-dihydroxyvitamin D3 on intestinal disaccharidases in uremic rats.

The effect of 1,25-dihydroxyvitamin D3 (1,25-D) on the activity of intestinal disaccharidases, maltase, sucrase, trehalase and lactase, was studied in five-sixths nephrectomized uremic rats. In uremic rats, maltase, sucrase and trehalase activities were lower than in sham-operated rats. Administration of 1,25-D produced significant improvement of maltase, sucrase, trehalase and lactase activities in uremic rats. These results suggest that activities of intestinal disaccharidases are reduced in uremic rats and these activities are normalized after 1,25-D administration.