Turnover of free and conjugated serum catecholamines during hemodialysis.

The response of the catecholaminergic system was evaluated in uremic patients maintained on a chronic outpatient hemodialysis (HD) program. Serum concns of free and conjugated catecholamines (CA) were measured prior to and following HD and in response to upright posture, and were compared to values obtained in a normal group of individuals submitted to the same stimuli. Before HD, the level of free plasma dopamine (DA) (155 +/- 58 pg ml-1) was comparable to that of normal individuals (38 +/- 12 pg ml-1) due to the large number of individuals of the 2 groups having undetectable serum levels. Free norepinephrine (NE) and epinephrine (E) serum levels were higher, before HD, in uremic patients (301 +/- 31 and 139 +/- 43 pg ml-1) than in normal individuals (206 +/- 14 and 34 +/- 4 pg ml-1). Serum concns of the 3 forms of conjugated CA, before HD, in uremic patients were markedly elevated (35,800, 9644 and 1374 pg ml-1 for DA, NE and EPI, respectively), compared to those in normal individuals (1885, 1374 and 65 pg ml-1). Only the serum level of free NE was elevated (from 301 to 600 pg ml-1) due to the rapid fluid loss that occurs during HD. On the other hand, a drastic decrease in the serum level of conjugated DA (16,020 vs 35,794 pg ml-1), NE (4282 vs 10,596 pg ml-1) and E (688 vs 1294 pg ml-1) occurred during HD. It is suggested that uremic patients lose their normal catecholaminergic response to upright posture at the end of HD treatment as a result of a progressive depletion of their free CA storage that cannot be supplemented from the large quantity of conjugated CA still available in the serum under such circumstances.

Primary nephrosis in childhood associated with focal glomerular sclerosis: is long-term prognosis that severe?

In our study, 32 nephrotic children with focal glomerular sclerosis were observed for an average period of 8 years (ranging 1-19 years of age). Of the 32, 25 children showed histological lesions of focal segmental sclerosis (FSG) and 7 of focal global glomerulosclerosis (FGG). All patients were reevaluated in 1979, creating the most recent status as follows: for children with FSG, 6 (24%) are in remission, 10 (40%) have a relatively normal renal function but exhibit either a persisting proteinuria (PP) or a recurrent nephrotic syndrome (NS), 1 (4%) is in chronic renal failure, 5 (20%) required dialysis and transplantation, and 3 (12%) died from non-renal causes. For children with FGG, 4 (57%) are in remission, 2 (29%) have a good renal function but display either PP or NS, and 1 patient (14%) is in chronic renal failure. The long-term observation of our study shows a more favorable prognosis than the one reported in researched literature. We believe that such results reflect a difference in the type of population encountered in our institution. Our population of patients represents less a highly referred population than the one of the centers who reported similar long-term studies, and we believe therefore that our study may represent a wider spectrum of the natural history of the disease. Moreover, the group of patients with PP or NS does not show a progressive decrease of glomerular filtration rate with time, which suggests that the disease may progress in a stepladder fashion.

Determination of free and conjugated catecholamines and L-3,4-dihydroxyphenylalanine in plasma and urine: evidence for a catechol-O-methyltransferase inhibitor in uraemia.

A sensitive, accurate and reproducible method has been developed for the determination of free and conjugated catecholamines and L-3,4-dihydroxyphenylalanine in plasma and urine. The assay involves the enzymatic conversion of these compounds to their radio-labelled O-methylated derivatives using catechol-O-methyltransferase and S-adenosyl-L-[methyl-(3)H]methionine. Recoveries of 75 + /- 5% for dopamine, 70 + /- 5% for adrenaline and 65 + /- 5% for noradrenaline were obtained. The sensitivities were 0.5 pg for adrenaline and noradrenaline and 5-7 pg for dopamine, and dihydroxyphenylalanine. Measurements of conjugated catecholamines were performed after mild acid hydrolysis for 20 min at 95 degrees C. During this procedure no degradation of the catecholamines was observed. This assay led to the discovery of a dialyzable factor in the plasma of chronic uraemic patients which inhibits catechol-O-methyltransferase activity in vitro. The mean 22% inhibition observed for unhydrolyzed plasma increased to 42% after hydrolysis. The identity of this inhibitor which exists as an inactive conjugated form, probably a sulphate ester, and its implication in physiopathological disorders remain to be established.

Inhibition of cell proliferation in the livers of hepatectomized rats by a rabbit hepatic chalone.

A purified chalone isolated from rabbit liver was tested in vitro on regenerating rat liver slices incubated with tritiated thymidine to determine more precisely the phase of the normal cell cycle that was blocked by that substance. Biochemical and radioautographic studies showed that the inhibition of tritiated thymidine incorporation during chromosomal DNA replication resulted chiefly from a block in the G(1)-S transition in the normal cell cycle. Under these conditions the chalone had little inhibitory effect on hepatocytes that were in the S phase of the cell cycle. The inhibitory effects of the liver chalone appeared to be specific for hepatocytes and no significant inhibition of cell division was observed when that compound was tested against intestinal villi or tongue epithelial cells of the rat. When, on the other hand, the purified chalone was injected into rats following partial hepatectomy, not only was an inhibition observed during the G(1)-S transition but an increase in the ratio of metaphases to anaphases was found, suggesting that a block also occurs at metaphase as a result of the action of the purified liver chalone used in this study. The injection of a crude supernatant fluid obtained from rabbit liver homogenates into partially hepatectomized rats resulted not only in a more pronounced block at the G(1)-S transition than was observed when the purified chalone was used, but the supernatant liquid also affected significantly DNA synthesis during the S phase of the cell cycle. These inhibitory effects were observed not only in hepatocytes but in intestinal epithelium and tongue epithelial cells of the rat as well. The rabbit liver supernatant fluid thus appears to contain, in addition to the liver chalone, one or more nonspecific inhibitors of DNA synthesis.