Studies on renal excretion of potassium in the dik-dik antelope.

1. In a study on the renal handling of potassium by the dik-dik antelope, plasma and urine samples were analysed for potassium, sodium and creatinine concentrations and osmolality during dehydration and intra-ruminal loading of potassium solutions. 2. The fractional excretion of potassium was 0.64 during the control period and rose up to as high as 2.3 during potassium loading. Urinary osmolality and potassium concentration decreased as the urine volume increased but the total amounts of potassium excreted were independent of urine volume. 3. Potassium loading led to a steady increase in its urinary excretion but a decrease in plasma potassium concentration was observed. This observation casts doubt on the hypothesis that alterations in potassium intake produce parallel alterations in plasma potassium concentration (which supposedly stimulates or depresses potassium excretion) and thereby maintain potassium homeostasis. 4. A possible alternative signal for increased potassium excretion following increased intake is discussed.

Physiology of the dik-dik antelope.

1. The East African dik-dik antelope represents a miniature model ruminant for comparative studies. 2. Dik-diks are browsers, consuming a diet consistently high in fermentable and digestable plant material. 3. Their foregut structure is designed for a relatively rapid passage of food and effective absorption of fermentative products. 4. Dik-dik antelopes are very economical in their use of water, having a low daily water exchange and excreting a highly concentrated urine. 5. Dik-diks have been observed to employ three thermoregulatory mechanisms; thermopanting, active sweating and a labile body temperature. 6. Their reproductive cycle is polyestrous with peak breeding in June and December, having a gestation period of between 170 and 174 days.

Renal excretion of urea in a small east African antelope, the dik-dik (Rhynchotragus kirkii).

1. A study on the renal handling of urea by the dik-dik antelope (Rhynchotragus kirkii) was conducted. 2. Plasma and urine samples were analysed for osmolality, urea and creatinine concentrations during dehydration and intra-ruminal loading of potassium and sodium solutions. 3. The glomerular filtration rate (GFR) of the dik-dik was found to be 182.6 +/- 11.7 ml/min/100 kg body mass. 4. Dehydration was observed to increase tubular urea reabsorption and increase plasma and urine osmolalities, but had no effect on the amount of urea filtered at the glomerulus. 5. Potassium loading increased both GFR and urine flow rate.