ABSTRACT
Experiments were performed with young two-humped camels exposed to 36-hour starvation with free access to water. The renal functions were measured by the standard clearance method. In spite of the administration of 20 micrograms DDAVP, a higher urine flow rate was recorded in the camels subjected to control measurements (feed intake) than in the fasting period (1.45 +/- 0.06 vs. 0.96 +/- 0.06 ml . min-1, P less than less than 0.001). On the second day of fasting the camels had a significantly reduced glomerular filtration rate (GFR 317.5 +/- 23.2 vs. 170.2 +/- 17.4 ml . min-1, P less than 0.001), urea output (700.5 +/- 62.9 vs. 352.2 +/- 64.7 mumol . min-1, P less than 0.005), and fractional excretion of urea (26.9 +/- 2.8 vs. 17.9 +/- 1.7%, P less than 0.01), whereas their tubular resorption. of urea (Reab urea/GFR) increased (6.28 +/- 0.61 vs. 9.12 +/- 0.82 mumol . ml-1, P less than 0.02). No significant difference was found in the concentration of urea in plasma in the fed camels and in fasting camels (8.55 +/- 0.64 vs. 11.18 +/- 1.09 mmol . l-1, N. S.). The creatinine inulin clearance ratio (C creat/Cin) was 0.92 +/- 0.07 when the animals were fed and 1.17 +/- 0.05 when the animals starved (P less than 0.001); this suggests that the clearance of endogenous creatinine is not suitable for GFR measurement in camels under different conditions of nutrition. The kidneys of camels regulate the excretion of urea during short-time fasting mainly through the reduction of glomerular filtration rate and just partly through an increased tubular resorption.
