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Clinical insight
P R O B E
• V o l . L I I I • N o . 3 • A p r – J u n 2 0 1 4
confirmed in in vitro experiments with
CaOX concrements, performed in
confined volume and at physiological
flow conditions, which correspond
to a possible in vivo experiment in a
human kidney pelvis.
Not only does it even seem that HA
is the natural regulator of CaOX
supersaturation in human urine, but
it also appears to be such a regulator
in mammal urine, in general.
This follows from other known
experimental findings on the very low
Figure 2.
Metabolic Pathway of Oxalic Acid
frequency of calcium oxalate stone
formation in herbivorous mammals.
The concentration of HA in mammal
urine is, as a rule, considerably higher
than its level in human urine. A
classical and well-studied case in this
respect gives the urine of horses (from
where Justus von Liebig derived the
name of hippuric acid, many years
ago).
Taking into account the metabolism
of benzoic acid and its salts, as
described above, a good alternative
for metaphylaxis of the CaOX
precipitation of nutrients would
be added to the sodium benzoate.
According to the so called hepatic
sample of Quick, taking 4 g of
sodium benzoate with tea, leads to
separation of 6 g of hippuric acid.
Sodium benzoate is found in many
berries, some formulations, and so
forth, so it is not difficult to raise the
urinary excretion and to establish an
appropriate diet or medication.
One should expect that by
administering and applying benzoic
acid, for a short period of time, a
considerable higher concentration
of HA in stone formers with CaOX
calculi, corresponding to the
physiological norm of this substance in
urine, could be and is in fact achieved.
Thus, a negative supersaturation with
respect to CaOX precipitation, and
even the direct dissolution of CaOX
calculi situated in the kidney pelvis,
or elsewhere in the urinary tract,
could be expected. One proof of this
is achieved by our in vitro results of
solubility of about 30 mmol/L stone.
The role and influence of drugs,
containing BA derivatives, which may
provoke such effects could be of great
importance to a future medication.
The amount of benzoates in a drug
treatment will be the subject of future
research. However, the important fact
is that the salts of BA are contained
in a number of berries and it may
advantageously be applied as an
appropriate diet for the prevention of
CaOX nucleation.
Atanassova SS, et al.
Regulation of Supersaturation in Calcium Oxalate Lithiasis
Table 3. Hippuric Acid as a Solvent of Calcium Oxalate—Comparison With
Classical Complex-forming Agents
Ligand
Complex-
former
Solution
Temperature
°C
pH
K
i
, L/mol
Na-EDTA
Ca
2+
Physiological
solution
25
7
5.0 × 10
5
Mg
2+
C
2
O
4
2-
0.3M NaCl
37
NA
5.6 × 10
3
Mg
2+
C
2
O
4
2-
0.3M NaCl
25
5
4.0 × 10
3
Citric Anion
Ca
2+
Pure water
25
NA
5.0 × 10
2
Hippuric Acid
Ca
2+
Zero
saturated
artificial
urine
25
5.5
7.0 × 10
3
NA, not applicable.
Ethanolamine
Serine
Glycine
Glycolic
Glycolate
Ascorbate
Aldehyde
2-oxo-4-hydroxyglutarate
2-hydroxy-3-oxoadipate
2-oxo-3-hydroxyadipate
2-oxyglutarate
Hydroxyproline
Glyoxylate
Oxalate
