R. Jontofsohn, and It Kiuthe,’

content 2

M.D., M.D.

G. Trivisas,

ABSTRACT

The

(serum

regular

hemodialysis, and

compared whereas

alanine.

of erythrocytes

same

gradient

be due

to loss ofuremic

the

for

with

for glutathione support

this

It is well known that disturbances of amino acid (AA) metabolism occur in uremia. Most studies deal with AA imbalance in plasma (1-5), a few studies on the AA content of muscle have also been performed (6). Ganda et al. (7) described changes in the AA levels of the erythrocytes of uremic subjects similar to those seen in the plasma. Since the metabolism in erythrocytes is less complex than in other cells we considered it worthwhile to investigate the changes in AA metabolism occuring in the erythrocytes of uremic patients. Materials Three

and groups

methods were

investigated,

15 patients

with

were

increased

se-

controls.

synthesis

1956

The American

JournalofClinical

Nutrition

and

in red cells.

hypothesis.

Am.

cells

High

J. Clin.

as

alanine

from

uremic

group

the cysteine

erythrocytes

of 3.5:1.

of the elevation

The low cysteine

in their

plasma

levels in erythrocytes glutathione

Nuir.

31:

levels 1956-1960,

in the 1978.

and deproteinized with sulfosalicylic acid in one step. The subsequent handling was the same as that for the measurements of plasma AA content. The AA were measured by ion exchange chromatography on an AA analyzer using the ion exchange resin DC-6 A (Durrum, Palo Alto/CaliL), column size 30 x 0.9 cm. The elution was performed with lithium citrate buffers according to a modification of the method of Kedenburg (9). The evaluation of the spectrophotometric curves was performed by an on line integrator Autolab System (Spectra Physics). The coefficient of variation of this method for the different AA ranged between 1.2 and 3%. Using the methods described above it was not possible to measure the aspartic acid content of whole blood as the peaks of glutathione and aspartic acid coincided. Furthermore in some chromatograms there were difficulties in separating the peaks for glutamine and glutamic acid. These AA were, therefore, not considered in this paper. The AA content of the erythrocytes was estimated using the formula:

vere renal failure, serum creatinine < 8 mg/ 100 ml, treated with selective low-protein diet (potato egg diet, according to Kluthe et al. (8), 13 patients on regular hemodialysis (two to three dialyses/week) on a so-called “free diet”, and 1 1 healthy subjects serving as controls. Two blood samples were taken from each. subject and placed in EDTA tubes. The hematocrit was measured in each specimen. One sample was centrifuged immediately and the plasma deproteinized with sulfosalicylic acid (final concentration 3%) The pH was adjusted with a sodium citrate buffer to pH 2.2 and the samples stored at -30 C until analysis. In order to determine the AA content of whole blood, the specimens were hemolyzed

plasma

in spite

in

reduced Alanine

of normal

of red

In the control

between

patients

is increased

constantly controls.

in spite ratio

to alanine.

a gradient

with

increased

on

acids

of histidine,

level

serine was from healthy

glycolytic

amino

exception

the

renal

severe in patients

Most

erythrocytes

plasma differ

with diets,

studied.

with

the

the not

transamination

of 2.7 compared

patients

levels,

patients

in uremic

were

as in plasma

plasma

to the

in patients low-protein

subjects

changes

of uremic be due

decreased

of cysteine

selective

uremic patients erythrocytes did

be observed

levels by a factor

erythrocytes

In

may

was

same

erythrocytes

and with

of healthy

histidine

of low

pyruvate

could

treated

group the

erythrocytes

more

delivering

cysteine may

in the

of plasma ml)

showed

In spite

M.D.,

content

in a control

levels. This fmding

subjects The

acid

8 mg/100