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Erythropoietin (EPO) formation in kidneys of 18 patients with autosomal dominant polycystic kidney disease (ADPKD) was investigated. In 12 patients on hemodialysis and in 6 patients with preterminal renal failure serum, EPO was 29±7 and 16±1.5 mU/mI and hemoglobin concentrations were 11.0±0.6 and 12.7±1.2 g/dl, respectively. Cyst fluid from a total of 357 renal cysts was obtained by either in vivo aspiration or immediately after nephrectomy. The cysts contained variable concentrations of bioactive EPO from undectable values up to 3.2 U/ml. A pronounced enrichment of EPO was observed in cysts with sodium concentrations > 100 mmol/liter, suggesting an association with proximal tubular malformations. The EPO concentrations in the cysts were neither c orrelated with the protein concentration nor with the oxygen pressure of the cyst fluid. Using a cDNA probe for human EPO, mRNA for EPO was localized in stroma cells of the cyst walls by an in situ hybridization technique. Our findings suggest that single interstitial cells juxtaposed to proximal tubular cysts may produce EPO independent of the oxygen pressure inside the cysts, which ameliorates the anemia during end-stage polycystic kidney disease.

Dialysis-related amyloidosis is characterized by various imaging appearances. In evaluating amyloidosis, MRI provides considerably more information than that obtained from conventional radiographic, CT, and sonographic studies.

The detection of characteristic radiographic signs in CAPD patients presenting with symptoms of intestinal obstruction may suggest the presence of severe SP and should lead to cautious surgical interventions.

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The mechanism of increased serum creatinine after administration of pyrimethamine and dapsone was evaluated for six healthy volunteers. Serum parameters, urine sediment, and clearances of creatinine, inulin, and para-aminohippurate were assessed prior to and 28 h after the ingestion of a single, combined dose of 100 mg of pyrimethamine and 200 mg of dapsone. In a second series, the same renal function tests were performed for nine human immunodeficiency virus-infected men before and after 1 month of prophylactic treatment with a weekly dose of 75 mg of pyrimethamine and 200 mg of dapsone to evaluate sustained effects on renal function. Serum creatinine increased within 28 h from 81 14 to 102 + 16 ,umol/liter (P = 0.002) in the healthy volunteers. Blood urea nitrogen, 132-microglobulin, and urine remained normal. Creatinine clearance decreased from 125 + 27 to 91 ± 26 ml/min (P < 0.02) without changes in inulin clearance. The effect was reversible within 21 days and attributable to pyrimethamine, as determined by administration of each drug alone. The sustained effect of four doses of pyrimethamine and dapsone in human immunodeficiency virus-infected patients consisted of an analogous rise in serum creatinine from 69 17 to 87 + 32 ,umol/liter (P < 0.05). Both creatinine and inulin clearances, however, were unchanged, representing a new equilibrium between creatinine production and elimination at a higher level in serum. Pyrimethamine, thus, may reversibly inhibit renal tubular secretion of creatinine without affecting the glomerular filtration rate. This physiologic effect in pyrimethamine-treated patients must be differentiated from possible organ-related nephropathies.