Renal functions in hens fed graded dietary levels of ochratoxin A

Renal pathology of the fowl--a review

On the basis of published literature and some original observations a comprehensive review is presented of the current concept of renal diseases in the fowl. All aspects of this important but much neglected subject are considered including autolysis, intoxications, inflammatory and degenerative conditions, specific viral diseases, gout, congenital abnormalities and neoplasms. The aetiology and pathogenesis of some forms of avian kidney disease are well understood but there are large gaps in our knowledge on others.

Comparison of renal and salt gland function in three species of wild ducks

Three processes central to osmoregulation of marine birds were compared in three species of ducks that differ in habitat affinity, diet and saline tolerance. These processes are filtration of Na+ and water from the plasma by the kidneys, their reabsorption along the renal tubules, and secretion by the salt glands. Barrow's goldeneyes Bucephala islandica, the most marine species, have the highest rates for all three processes and only this species can secrete all the infused salt via the salt glands. Rates of all three processes are lower in mallards Anas platyrhynchos, the most freshwater species. Following saline acclimation, mallards could excrete all the infused Na+ by a combined Na+ excretion of the kidneys and salt glands. Canvasbacks Aythya valisineria, despite being more saline tolerant than mallards, are unable to excrete all the infused Na+. They produce a large volume of urine (like mallards) that has a low [Na+] (like goldeneyes). Salt gland secretion Na+ concentration did not differ among the three species, but only goldeneyes secrete at a rate sufficient to eliminate all infused Na+ via the salt glands. Differences in saline tolerance of these ducks species cannot be fully explained by differences in their filtration, reabsorption and secretion of Na+ and water, suggesting that the intestinal tract plays an important role.

Immunosuppression due to chronic ochratoxicosis in broiler chicks

Crystalline ochratoxin A (OA) was added to the feed of broiler chicks at 0.5 ppm and 2.0 ppm, and humoral and cell-mediated immunity (CMI) were studied. CMI was assessed by skin sensitivity testing, graft versus host (GVH) reaction and T lymphocyte count. Humoral immunity was examined by measuring the haemagglutinin (HA) response to sheep RBC (SRBC). In addition, total lymphocyte counts, total serum protein, albumin and globulin were determined and the phagocytic activity of splenic macrophages was measured in the nitroblue tetrazolium test (NBT). The weights of lymphoid organs were also recorded at post-mortem examination of the birds. Highly significant reductions in CMI were indicated by diminished skin sensitivity, GVH reactions and T lymphocyte counts. On the other hand, only the overall HA titres differed significantly between the various treatment groups. Total lymphocyte counts, total serum protein, serum albumin and serum globulin were significantly depressed on the 21st day of intoxication. The number of NBT-positive cells was drastically reduced in both the intoxicated groups compared with controls (P less than 0.05) and the weights of thymus, bursa of Fabricius and spleen of intoxicated birds were significantly reduced. The study illustrated the immunosuppressive effects of ochratoxicosis in broiler chicks.

Effects of chronic ochratoxin A and citrinin toxicosis on kidney function of single comb White Leghorn pullets

The objectives of the present study were to examine the effects of repeated or chronic ochratoxin A (OA) and citrinin exposure, and to determine if severe ochratoxicosis permanently alters renal function in pullets. The OA-treated birds were injected intramuscularly (breast muscle) with a 1 mg/mL solution of OA at a dose of .25 mg/kg BW or .5 mg/kg BW. Citrinin-treated birds were injected with a 6 mg/mL solution of citrinin at a dose of 6 mg/kg BW. Control birds received an equal volume injection of the citrinin and OA solvent, 100% ethanol, at a dose of 1 mL/kg BW. Kidney function was evaluated after 10 consecutive days of OA, citrinin, or ethanol injection, and 2 wk following the final injections. Venous blood gas measurements were taken after the seventh day of injection. The OA increased urine flow rate, decreased urine osmolality, increased ion excretion (Na, K, Ca, P), increased water consumption, increased manure moisture, and caused a relative alkalosis when measured immediately after 10 days of OA injection. These effects of OA were not detected 2 wk later. Citrinin increased manure moisture, decreased plasma P, increased the clearance of para-aminohippuric acid, and had no consistent effect on blood acid-base parameters. The results suggest that OA may cause an osmotic diuresis by inhibiting tubular reabsorption of electrolytes. The data also suggests that the effects of OA may be reversible simply by discontinuing toxin administration. Although the citrinin-induced increase in manure moisture indicates that citrinin had an effect on renal function, renal function analysis suggests that even repeated exposure to high doses of citrinin may only have a short duration of diuretic action on the kidneys.

Effects of ochratoxin A alone and in combination with citrinin on kidney function of single comb White Leghorn pullets

The present study was designed to evaluate the acute effects of ochratoxin A (OA) on pullet renal function, and to determine if the diuretic effects of citrinin are altered by acute ochratoxicosis. Birds were injected intramuscularly with a 1-mg/mL solution of OA at a dose of 5 mg/kg body weight for 2 consecutive days. Control birds received an equal volume injection of the OA carrier vehicle (100% ethanol). On the 3rd day, birds were anesthetized and prepared for renal function studies. Following 30 min of control urine and plasma collection, an intravenous infusion containing 400 ppm citrinin was initiated, and urine and plasma were collected for an additional 70 min. The OA alone caused an increase in manure moisture and increased hematocrits (hemoconcentration), but direct effects on glomerular filtration rate (GFR), urine flow rate/GFR, para-aminohippuric acid clearance (CPAH), free water clearance (FWC), and electrolye excretion (Na, K, Ca, P) were not consistently demonstrated. The OA may cause hemoconcentration by causing a subtle increase in urine flow (diuresis), or by increasing intestinal water loss (diarrhea). Citrinin infusion caused increased urine flow rate, increased urine flow rate/GFR, increased FWC, increased Na excretion, and decreased urine osmolality. Pretreatment with OA attenuated these effects of citrinin, presumably due to renal compensation for the OA-induced hemoconcentration. Citrinin and OA do not appear to have additive diuretic effects during the first 48 h of toxin exposure.

A modified Sperber technique for direct estimation of true renal tubular excretion fraction

The Sperber technique in the hen is particularly suitable for the study of renal tubular secretion. However, results obtained with this technique vary considerably, due to an unpredictable and highly variable shunting of renal portal blood. In an attempt to get a total and stable renal perfusion by portal blood from the leg, appropriate shunt vessels were ligated. This procedure was found to force all portal blood from the leg to perfuse the ligated kidney, without affecting the symmetry of glomerular filtration or renal clearance of 125-I-Na-o-iodohippurate between the kidneys. In conclusion, the abolition of renal portal shunt flow allows use of the Sperber technique for a direct estimation of the true tubular excretion fraction (TTEF) of a substance. Thus, TTEFPAH, a measure of the tubular excretion efficiency of para-amino-hippuric acid, was found to be about 70%. The stable renal perfusion in ligated animals will also facilitate comparative studies of renal tubular excretion in the hen. Moreover, no animal has to be rejected due to a low renal perfusion of portal blood. Furthermore, the use of ligated hens makes it unnecessary to use markers for the renal perfusion of portal blood when steady-state experiments are performed. Finally, the total renal perfusion of portal blood in ligated animals will facilitate the demonstration of a secretory component in the renal handling of substances with a low affinity for the renal transport system.

Ochratoxicosis in White Leghorn hens

As ochratoxin-producing fungi are often isolated from poultry feeds and from cereals used in compounding these feeds, a study has been made of the effects of feeding ochratoxin A (OA) to laying birds. Four groups of White Leghorn hens were fed 0, .5, 1, and 4 ppm in the feed respectively. Egg production and feed consumption declined in the three groups given OA, while egg and body weight were depressed only by feeding higher levels of OA. Fertility and hatchability were unaffected by feeding OA. Prothrombin times were increased and total serum proteins were decreased after feeding 1 or 4 ppm for six weeks. After the withdrawal of the mycotoxin-contaminated feed, OA disappeared from the muscle after 24 hr but persisted in liver and kidney for more than 48 hr. No residues were found in fat or skin.

Blood flow distribution in the renal portal system of the intact hen. A study of venous system using microspheres

The blood flow in the renal portal system of intact hens was characterized by determining the fractional distribution of 15 microns and 50 microns microspheres in this system after injection into a leg vein. Validation tests showed that only 50 microns spheres gave reliable estimation of this distribution. The blood flow in the coccy-geomesenteric vein was directed towards the liver in nearly all cases. On the average 44, 47 and 8% of the portal blood from the external iliac vein perfused the ipsilateral kidney, the liver and the lungs, respectively. However, the distribution of portal blood to these organs varied considerably between individuals and changed appreciably within 35 min in half the animals studied. The reason for these variations is not clear. The portal blood from the right and left external iliac veins was asymmetrically distributed in most animals illustrating the importance of local factors in its regulation. Variation was great in the regional distribution of portal blood within the kidney possibly due to local vasoconstriction of portal vessels. Further information e.g. on the regulation of renal portal blood flow is needed to explain its physiological significance. Microspheres provide a convenient method for such studies. A combination of microsphere and Sperber techniques allows us to determine the renal excretion efficiency of a given substance.