Page 129 - Aussie Magazine - 2023 Issue 2

Allantoin is the end product of purine catabolism
in all mammals with the exception of man, apes
and Dalmatian dog breed. Man and Dalmatian
dogs produce uric acid resulting in increase of
uric acid concentration in blood and urine and
can cause serious health problems. However,
the mechanism of production of high levels
of uric acid concentration in blood is different
in both kinds. In kidneys of man and apes, the
uric acid is filtrated in glomeruli and part of it is
reabsorbed in proximal tubules, where it enters
again into the circulation. During the evolution
of primates, several nonsense mutations of
uratoxidase enzyme were substituted (catalyses
the enzymatic oxidation of uric acid to allantoin),
which led to suppression of enzyme function
and to increase in concentration of uric acid in
blood and urine. The uric acid circulates as free
uric acid or uric acid salts in plasma, where it
serves as free radical. The uric acid predisposes
the man to uric acid stone formation and gout.
The Dalmatian dog breed has lost the ability of the bladder, in which case you may see blood
Text written by: Martina Svecova. Photographs provided by: Veronika Follaufova, Monika Peliskova
reabsorption of uric acid in the proximal tubule in the urine, difficulty and pain in urinating and
thanks to mutation in urate transport protein; small, frequent amounts of urine. Urinary tract
the excretion of uric acid equals to or exceeds obstruction is a serious condition that occurs
the rate of glomerular filtration. In Dalmatians, when a stone completely blocks the urethra and
a defect in urine metabolism caused that the blocks the outflow of urine (more common in male
Dalmatians excrete the uric acid instead of dogs that have a smaller urethra). Signs include
allantoin. The uric acid forms uric acid stones in straining to urinate, vomiting and loss of appetite,
Dalmatians. This trait was probably fixed in the weakness and lethargy (lack of energy), due to
breed through selection for a more distinctive toxins building up in the body.
spotting pattern. The specific pattern of their
coat has been created by at least three various Recently, a DNA-test is available that reliably
mutations: reveals the gene that is responsible for excessive
• a mutation for white coat colour (MITF gene, excretion of the uric acid in urine. Hyperuricosuria
Karlsson et al. 2007), in dogs is caused by single nucleotide exchange
• a dominant mutation at the T-locus causing of c.G563T (p.C188F) in SLC2A9 gene (gene
spotting (Little 1957), for urate transport) (Bannasch et al. 2008). The
• a mutation influencing the spot size - just disease is described as an autosomal-recessive
with this mutation is probably segregated condition. This means that a dog must inherit
the mutation responsible for the occurrence two copies of an abnormal gene (one from its
of hyperuricosuria (Schaible 1976). mother and one from its father) before its health
is affected. A dog that inherits only one copy of
The changes in the urine are generally present the abnormal gene (from its mother or its father)
from birth. However it usually takes some time will have no signs of the disease, but will be a
for crystals to form and combine into stones carrier and may pass the gene on to any offspring.
that cause problems, most often between 3 and
6 years of age. The signs you will see in your Almost every dog of Dalmatian breed with
dog depend on where in the urinary tract the the exception of LUA Dalmatians suffers from
stones end up. They collect most commonly in hyperuricosuria – affected homozygotes – having

A Worldwide Magazine for the Aussie • Issue 2/2023 | 129