The Distribution of Enzymes in the Kidneys of Sheep Fed a High and Low Protein Diet

Abstract

The distribution of 13 enzymes in the cortex, in the outer medulla and in the inner medulla of kidneys was investigated in sheep fed a high (HP) and low (LP) protein diet. Sheep on HP·diet were given a daily ration with 150.2 gofcrude protein (CP) and 15.2 MJ of digestible energy (DE) while the daily intake of sheep on LP·diet was 58.3 g ofCP and 14.2 MJ of DE. Both groups of animals were fed these diets for at least 6 weeks before the collection of kidneys. Histochemical analysis of enzymes showed that glucose·6·phosphatase and 5' ·nucleotidase were not detectable in the kidney Of sheep fed the HP·diet but they appeared in both the cortex and the outer stripe of the outer medulla of sheep on the LP·diet. Alkaline phosphatase of the inner stripe of the outer medulla and of the base of papilla was found in sheep fed the HP·diet only. Adenosine triphosphatase of the inner medulla appeared in sheep fed the LP·diet only. Changes in the distribution of other studied enzymes were only of a small magnitude. The present results demonstrate the enzyme expression of metabolic adaptation of sheep kidney to a low protein intake associated with an increased renal urea reabsorption. Histochemistry, kidney tissue, renal, metabolic adaptationThe sheep kidney plays an important role in many metabolic and biochemical pathways, mainly in gluconeogenesis, both from amino acid and non-nitrogenous glucose precursors. The adaptive changes in metabolic activity of sheep kidney associated with a modified renal function due to altered dietary protein intake are not fully understood yet. Protein intake in sheep and also in other ruminants has a significant effect on the renal concentrating ability (S chm idt-N ie I sen 1979), on the urea reabsorption in tubules (Faix et al. 1988a) and in renal pelvis (C iri 0 and B oi v i n 1990) as well as on glomerular filtration rate (Leng et al. 1985; Faix et al. 1988b;Skrzypczak et al. 1996). Just an increased delivery of some amino acids to sheep kidney due to their direct intrarenal infusion can induce a considerable change in many renal functions (Leng et al. 1994). The adaptation of sheep kidneys to an increased renal reabsorption of urea during low protein intake is expressed also by morphological changes in the epithelium in some nephron segments in both the cortex and medulla (Kocisova et al. 1997). Therefore it may be assumed that renal urea retention in sheep is accompanied also by changes in expression of enzymes in the kidney tissue.The existence of major biosynthetic and catabolic pathways of intermediary metabolism in the mammalian kidney has been known for a long time. Metabolism of the renal cortex is characterized mainly by fatty acid oxidation and gluconeogenesis (Weideman and Address for correspondence:MVOr. Zita Faixova. esc. Kre b s 1969). In contrast, the renal medulla as the kidney compartment with the largest urea recycling, reveals a high rate of aerobic and anaerobic glucose metabolism and it probably depends on glucose as a respiratory fuel (Lee andPeter 1969; A bodeely and ...

Short-term vasopressin analogue treatment does not influence the nitrogen balance in sheep

“…The microbial population in the forestomachs enhances utilization of nitrogen from recycled endogenous urea. Thus, the kidneys of ruminants contribute to a N saving mechanism for protein synthesis (Faixová et al, 1998). These data confirm the important role of the ruminant kidneys in nitrogen metabolism.…”

The Kidney Function in Urea Loaded Sheep Fed a High Protein Diet

“…On the other hand, in ruminants the presence of large microbial population in the forestomachs enhances their potential to utilize nitrogen sources, including ammonia arising from the recycling of endogenous urea. Thus the kidneys of ruminants contribute to the conservation mechanism of nitrogen for a potential proteosynthesis (Faixová et al 1998). This statement on the special role of the ruminant kidneys in nitrogen metabolism is supported also by an unaffected renal urea clearance in our urea-infused sheep.…”

The Renal Response of Sheep Fed a High Protein Diet to Treatment with Vasopressin Analogue

“…The adaptation ability of sheep kidneys to a reduced delivery of protein by food includes the morphological (Koãi‰ová et al 1997), biochemical (Faixová et al 1998) and functional response (Leng et al 1985) in order to increase the renal urea reabsorption for its subsequent recycling through the digestive tract. The main change in renal function responsible for a high urea retention in sheep appears to be a significant reduction of glomerular filtration rate (GFR, Leng et al 1985;Cirio and Boivin 1990).…”