| dc.description.abstract | A study to examine the glomerular filtration rate,
renal mechanisms for potassium, sodium and urea excretion,
urine osmolar concentration as well as saline drinking
abilities of the dik dik antelope was carried out under
controlled laboratory experiments.
Observations were made on the daily intake and excretion
of electrolytes (K and Na) by dik diks fed only once daily
and housed in metabolism cages. Food and faeces were
analysed for dry matter, ash and electrolytes contents.
Urine and plasma samples were analysed for osmolality, K,
Na, Urea -N, NH3-N and Endogenous true creatinine
concentrations during control and various treatments.
In the control state, 73% of the total K recovered in
both urine and faeces was excreted in urine while urine Na
represented only 11% of the total Na recovered in urine and
faeces. Renal tubular reabsorption for K, urea and Na was
39.9%, 55.3% and 99.9% of the filtered quantities,respectively ..
The glomerular filtration rate varied from 3.4 to 16.8 with
a mean of 7.2 ml/min. Urine osmolality, K, Na, urea and
creatinine concentrations varied inversely with the urine
volume.
Dehydration was accompanied by significant de..crease of
glomerular filtration rate (P< 0.05) and urine flow rate and
an increased tubular urea reabsorption. Solutes loading
however tended to have opposite effects. Potassium loading
on the other hand increased the ratio of potassium clearance
to creatinine clearance to over unity thereby reaching a
maximum of 2.0. This provided evidence for potassium
secretion by the antelope's renal tubules. Similarly1as
solute excretion rate increased, urine osmolality decreased,
resulting with the highest urine osmolality being observed at
the lowest rates of solute excretion. Dik diks offered
saline solutions as the only source of drinking water ranging
from 0.1 to 0.5 mole/l NaCI could tolerate only a concentration
of 0.3 mole/l NaCl.
The percentages and pattern of urinary potassium
excretion as well as faecal sodium excretion were similar
to the pattern found in both domestic and wild ruminants such
as sheep, cattle and red deer thus far studied. Tubular
potassium secretion was evidenced in the dik dik antelope and
explains its tolerance for rich-potassium diets without any
adverse effects. It was further observed that by increasing
tubular water reabsorption and decreasing glomerular
filtration rate, the dik dik antelope is able to excrete a
very highly concentrated urine (4200 mOsm/kg ri20) and conserve
water.
In the dik dik an te lopey as in the case of the mammalian
kidney in general, 99.9% of filtered Na was reabsorbed along
the renal tubules. The ability of their kidneys to increase
urea reabsorption during dehydration was of interest and
probably explains this species· ability to live in dry areas
and withstand prolonged periods of drought mostly encountered
in the East and Central African regions. | en |
