Erythrocyte sodium transport in dialyzed uremic patients

To investigate the status of the Na+ concentration and ionic fluxes in red cells of human subjects with dialyzed chronic uremia, the authors measured the Na(+)-K+ pump activity as well as Na(+)-K+ cotransport (CoT), Na(+)-Li+ countertransport (CTT) and Na+ passive permeability in erythrocytes from 37 normal subjects and 23 chronic uremic patients receiving maintenance hemodialysis. The mean intracellular Na+ concentration [Na+]i value in the pre-dialytic group was significantly lower than that in control subjects (p less than .0001), but tended to recover to the normal value of [Na+]i in the post-dialytic group. The mean intracellular K+ concentration value in the post-dialytic group was significantly higher than that of the control group (p less than .001), but not significantly different from that of the pre-dialytic group. It was found that the Na(+)-K+ pump activity of erythrocytes in the pre- and post-dialytic groups markedly decreased over that of the normal control group with statistical significance (p less than .0001, respectively). The Na(+)-K+ pump activity in the post-dialytic group, however, tended to recover, but not significantly. The rate constant for ouabain-sensitive Na+ efflux in the post-dialytic group was significantly decreased over that of the normal controls (p less than .05). The authors observed a significant decrease of the Na+ CoT value (p less than .001 respectively) and rate constant for Na+ CoT (p less than .05, respectively) in the patients with pre- and post-dialytic uremia vs. that of normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of adenylate cyclase in human keratinocytes by protein kinase C

Adenylate cyclase (ATP-pyrophosphate lyase (cyclizing); EC 4.6.1.1) in the human keratinocyte cell line SCC 12F was potentiated by 12-O-tetradecanoyl-phorbol-13-acetate (TPA), phorbol-12,13-diacetate, and 1,2-dioctanoylglycerol. Keratinocytes exposed to TPA showed a 2-fold enhancement of adenylate cyclase activity when assayed in the presence of isoproterenol or GTP. The half-maximal effective concentration (EC50) for both isoproterenol and GTP were unaltered by TPA treatment of the cells. Basal adenylate cyclase activity in membranes from TPA-treated cultures was also increased 2-fold relative to activity in control membranes. Potentiation of adenylate cyclase activity was dependent on the concentration of TPA to which the keratinocytes were exposed (EC50 for TPA = 3 nM). TPA actions on adenylate cyclase were maximal after 15 min of incubation of the cells with the compound, correlating well with the time course of translocation of protein kinase C (Ca2+/phospholipid-dependent enzyme) from cytosol to membrane. The action of cholera toxin on adenylate cyclase was additive with TPA. In contrast, pertussis toxin actions on adenylate cyclase were not additive with TPA. Treatment of control cells with pertussis toxin activated adenylate cyclase 1.5-fold, whereas cells exposed to pertussis toxin for 6 h followed by TPA for 15 min showed the same 2-fold increase in adenylate cyclase activity as observed in membranes from cells exposed to TPA without prior exposure to pertussis toxin. Pertussis toxin catalyzed ADP-ribosylation was increased 2-fold in membranes from SCC 12F cells exposed to TPA, indicating an increase in the alpha beta gamma form of Gi. These data suggest that exposure of human keratinocytes to phorbol esters increases adenylate cyclase activity by a protein kinase C-mediated increase in the heterotrimeric alpha beta gamma form of Gi resulting in decreased inhibition of basal adenylate cyclase activity.

The clinical utility of microalbuminuria in nephrotic syndrome with complete remission, isolated microscopic hematuria and renal transplantation donors

Using urinary microalbumin radioimmunoassay, we evaluated the clinical utility of microalbumin excretion in nephrotic syndrome with complete remission, isolated microscopic hematuria and kidney donors in reanl transplantation. The highest value in normal controls was 10.86 μg/min, and the upper normal level was set to 15 μg/min. The range of microalbuminuria in patients with nephrotic syndrome with complete remission was 1.67 μg/min to 32.5 μg/min. There was no significant correlation between the recurrence rate and microlbuminuria level in nephrotic syndrome with complete remission. The range of microalbuminuria levels in isolated microscopic hematuric patients was between 2.37μg/min and 103.2 μg/min. There was no singificant correlation between the amount of the red blood cells in urine and the level of microalbuminuria in the isolated microscopic hematuric patients. Most renal transplantation donors showed a normal range of microalbuminuria after nephrectomy. The aim of this study was to evaluate the clinical utility of urinary microalbuminuria in diseases other than diabetes. We concluded that further extensive and specific study will be required to determine the clinical utility of microalbuminuria.

Changes of plasma angiotensin-converting enzyme activity during hemodialysis

Plasma angiotensin-converting enzyme activity was measured by spectrophotometer in normal subjects and in patients with end stage renal failure, serially during a routine hemodialysis. Patients on maintenance hemodialysis tended to be associated with elevated plasma angiotensin-converting enzyme activity versus normal subjects. Plasma angiotensin-converting enzyme activity was significantly elevated in patients with chronic renal failure after 5 hours of hemodialysis(p<.001). Plasma angiotensin-converting enzyme activity corrected for hemoconcentration was also significantly increased(p<.05). There was a significant correlation between the increase in plasma angiotensin-converting enzyme activity after 5 hours of hemodialysis and the decrease in white blood cell count at one hour of hemodialysis (r = 0.51, p<.05). It is suggested that plasma angiotensin-converting enzyme analysis may prove to be a method for assessing transient pulmonary dysfunction during hemodialysis.