La chinchilla doméstica

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Datos urológicos de la chinchilla

No disponemos apenas de ningún estudio que permita establecer los valores urinarios de referencia válidos con fines diagnósticos. Os ofrecemos las únicas referencias que hemos podido encontrar que ofrezcan datos sobre los parámetros urinarios de las chinchillas.

 
1
2
3
Color    
amarillo a ámbar
Turbidez    
variable
pH
8,5
 
8,5
Proteínas    
trazas
Glucosa    
negativo
Nitratos    
negativo
Cuerpos cetónicos    
negativo
Bilirrubina    
negativo
Sangre    
negativo
Urobilinógeno (mg/l)    
1 - 10
Densidad (mg/ml)
> 1.045
 
1.045
Sedimento
Cristales de calcio
   
Producción de orina (ml/12 horas), machos en horario diurno  
4,8 - 5,6
 
Producción de orina (ml/12 horas), machos en horario nocturno  
8,4 - 10,4
 
Producción de orina (ml/12 horas), hembras en horario diurno  
3,0 - 4,0
 
Producción de orina (ml/12 horas), hembras en horario nocturno *  
2,0 - 2,8
 
Producción de orina (ml/hora/100g PV), machos en horario diurno  
0,104
 
Producción de orina (ml/hora/100g PV), machos en horario nocturno  
0,189
 
Producción de orina (ml/hora/100g PV), hembras en horario diurno  
0,060
 
Producción de orina (ml/hora/100g PV), hembras en horario nocturno *  
0,041
 
Presión osmótica (mOsmoles), machos en horario diurno  
7,050 - 8,650
 
Presión osmótica (mOsmoles), machos en horario nocturno  
9,950 - 12,010
 
Presión osmótica (mOsmoles), hembras en horario diurno  
5,240 - 6,940
 
Presión osmótica (mOsmoles), hembras en horario nocturno  
4,050 - 5,190
 
Cationes totales (meq/12h), machos en horario diurno  
1,198
 
Cationes totales (meq/12h), machos en horario nocturno  
2,749
 
Cationes totales (meq/12h), hembras en horario diurno  
1,376
 
Cationes totales (meq/12h), hembras en horario nocturno  
1,105
 
Cationes totales (meq/h/100g PV), machos en horario diurno  
0,039
 
Cationes totales (meq/h/100g PV), machos en horario nocturno  
0,055
 
Cationes totales (meq/h/100g PV), hembras en horario diurno  
0,023
 
Cationes totales (meq/h/100g PV), hembras en horario nocturno  
0,019
 
Sodio (meq/l), machos en horario diurno  
54,0 - 84,2
 
Sodio (meq/l), machos en horario nocturno  
90,0 - 112,8
 
Sodio (meq/l), hembras en horario diurno  
78,9 - 153,1
 
Sodio (meq/l), hembras en horario nocturno  
99,2 - 162,0
 
Potasio (meq/l), machos en horario diurno  
189,6 - 245,4
 
Potasio (meq/l), machos en horario nocturno  
124,0 - 170,8
 
Potasio (meq/l), hembras en horario diurno  
160,8 - 229,0
 
Potasio (meq/l), hembras en horario nocturno  
241,1 - 357,1
 
Magnesio (meq/l), machos en horario diurno  
72,2 - 81,4
 
Magnesio (meq/l), machos en horario nocturno  
45,7 - 49,7
 
Magnesio (meq/l), hembras en horario diurno  
68,9 - 86,9
 
Magnesio (meq/l), hembras en horario nocturno  
84,9 - 107,9
 
Calcio (meq/l), machos en horario diurno  
17,7 - 29,9
 
Calcio (meq/l), machos en horario nocturno  
6,5 - 11,13
 
Calcio (meq/l), hembras en horario diurno  
41,6 - 56,6
 
Calcio (meq/l), hembras en horario nocturno  
17,7 - 26,1
 
Cloruro (meq/l), machos en horario diurno  
91,8 - 136,4
 
Cloruro (meq/l), machos en horario nocturno  
48,2 - 67,5
 
Cloruro (meq/l), hembras en horario diurno  
169,6 - 213,0
 
Cloruro (meq/l), hembras en horario nocturno  
186,6 - 283,4
 
* La aparente discrepancia detectada en la producción urinaria de las hembras puede haberse debido a que los resultados no se estandarizaron respecto al estado reproductivo.

Los ritmos diarios en la composición de la orina son menos marcados en las hembras que en los machos. El patrón de eliminación urinaria, mayor durante la noche, se cree debido a que las chinchillas son animales nocturnos. La presión osmótica de la orina (1500 mOsmoles/l) es hipertónica respecto al plasma (300 mOsmoles/l aprox), aunque es menor que la encontrada en la rata por ejemplo. Sorprende que la orina de la chinchilla no sea más hipertónica dado el árido hábitat del que procede. Puede que se explique por el hecho de que la chinchilla utiliza los chorros de orina como mecanismo defensivo, lo que le obligaría a disponer de una cantidad copiosa de orina. Los estudios anatómicos comparativos de los riñones de los roedores indican que la capacidad de concentración urinaria está relacionada con el tamaño de la papila. El riñón de la chinchilla muestra una papila larga y voluminosa similar a la del jerbo o la rata canguro, que son dos roedores capaces de producir una orina muchísimo más hipertónica que el plasma. Es posible que la discrepancia entre la estructura renal y la capacidad de concentrar la orina del riñón de la chinchilla se deba a la selección artificial con fines comerciales, que ha podido producir numerosas alteraciones de su fisiología. Es probable que el anión más frecuente en la orina sea el bicarbonato, ya que el fosfato se ha detectado en pocas ocasiones y siempre en bajas concentraciones. La excreción de calcio es alta, especialmente durante el día. Al contario que en la rata la concentración de potasio es superior a la de sodio. No se cree que las dietas ricas en potasio sean la causa de esta elevada concentración de potasio en la orina. Es posible que los clásicos mecanismos de excreción renal del potasio no sean completamente aplicables a las chinchillas y demás histricomorfos. Las concentraciones de magnesio en la orina a menudo superan las de sodio. Se cree que la chinchilla tiene una extraordinaria capacidad intestinal para la absorción de magnesio. Sin embargo se deconocen los mecanismos que expliquen esta alta capacidad de absorción y excreción.

La concentración urinaria máxima con privación de agua o en respuesta a la administración de hormona antidiurética, es menor en la chinchilla que en la rata albina y no se observa reducción en la concentración urinaria de sodio bajo privación de comida en la chinchilla. Se está analizando la posibilidad de una sensibilidad alterada a la hormona antidiurética o a los mineralocorticoides. Un autor ha comentado que, comparada con otros roedores, C. laniger se parece a las especies desertícolas en su capacidad para extraer agua útil de soluciones concentradas de NaCl.

En la práctica clínica hemos observado gran variabilidad en el color de la orina. Desde orinas de color amarillento muy poco acusado a orinas de color rojizo intenso. Los cristales de calcio son frecuentes pero no están siempre presentes y la cantidad en que aparecen es muy variable. En las siguientes imágenes vemos la orina de 6 chinchillas mantenidas en la misma jaula y con la misma alimentación. Se puede apreciar el distinto color y el diferente grado de presencia de cristales de carbonato de calcio.


Están a nuestro alcance otros datos referentes a la funcionalidad renal que hemos podido hallar citados fundamentalmente en estudios urológicos referidos a otras especies animales, especialmente la rata. De momento os ofrecemos estos datos en inglés. Según los vayamos traduciendo los iremos poniendo en español.

4 This explicit model analysis of solute and water exchanges within the medulla confirms the general patterns that have been predicted based on anatomy and permeability data while pointing to some discrepancies, especially concerning the micropuncture data on urea absorption by short nephrons and the supposed profiles along the IMCD. A more serious problem pointing, in this author’s opinion, to some fundamental lack in the present formulation, is that this model and all previous models of this system predict a lower instead of steeper inner medullary gradient if permeabilities along the inner medullary LDL are raised, whereas these permeabilities are uniformly found to be higher in species that concentrate better than in those that do not. In a recent study aimed specifically at this question, Layton et al. (21) confirmed, in chinchilla kidneys, the high urea permeability of LDL under conditions resembling those in vitro as closely as possible. This issue thus remains central to the question of the inner medullary concentrating mechanism.

5 Water absorption from the descending limbs of Henle’s loop is of primary importance for the concentrating ability of the mammalian kidney, because ≈90% of filtered water is reabsorbed before it reaches the cortical collecting duct. Reports in the literature describe water- and solute-permeable descending limbs in hamsters, rats, chinchillas, and rabbits. The descending limb of Henle’s loop has been found in all species to be water permeable and moderately permeable to NaCl and urea. The adjacent ascending thin limb (ATL) of Henle’s loop is characterized by extremely low water permeability and very high chloride permeability.
Chou et al. showed that the osmotic water permeability of the descending limb in chinchillas is not uniformly high along its length. Instead, the distal 20% of the long-loop descending thin limb (DTL) was shown to have a relatively low water permeability (50 µm/s). Chou et al. also showed the NaCl and urea permeabilities to be nonuniform in the chinchilla descending limb, attaining a maximum in the innermost segment of 98.4 and 47.6 µm/s, respectively.
In vitro perfusion studies of thin descending limbs in hamsters, rats, and chinchillas have demonstrated a water-permeable descending limb. Low-tomoderate solute permeabilities have been measured for several species in DTL, e.g., sodium permeability in hamsters and NaCl permeability in chinchillas. In addition, little or no Na+,K+-ATPase activity has been recorded in thin descending limbs in the inner medulla, e.g., in rats. The measurements from perfusion studies and the data from immunolocalization suggest that mathematical models of the urineconcentrating mechanism might investigate a distribution of water- and solute-transporting segments of DTL on the basis of the distribution of AQP1 and ClC channels observed. Our observations, as well as those of others, show transitions from AQP1-positive to ClC-positive segments with no significant colocalization of solute and water channels. Hence, mathematical models might test the effect of water-permeable segments of DTL juxtaposed and in series with solutepermeable segments of DTL on solute concentration gradients in the inner medulla and on the kidney’s ability to concentrate urine.

6 High-Urea Permeability Parameter Values To further explore the impact of high urea permeability of LDL (Pu LDL), we also used a second parameter set, which was based mainly on permeability measurements in Henle’s loops of chinchilla (although some of the values are from the rat literature, because there is not a complete set of measurements for chinchilla). The chinchilla has been reported to concentrate its urine as high as 7,600 mosM. We will call this the “high-Pu” parameter set. Table 4 shows the values that are different from the baseline set. Here, we did not adopt the high value of LDL salt permeability used by Layton et al.
Here, we present the results of several key simulations demonstrating the effect of IM metabolic osmole production (glyocolytic conversion of glucose to lactate) in the flat medullary model described above. Using the baseline parameter set, we show that conversion of 15% of the glucose entering the medulla suffices to engender a sizeable IM osmotic gradient, mainly by amplifying the IM recycling of NaCl. We also show that this simulated osmotic gradient is essentially unaffected by raising the urea permeability of the thin descending limbs even to values several times higher than those reported in the microperfusion literature. Then, using a set of parameters corresponding more closely to the chinchilla kidney, which has an even higher value of Pu LDL than the rat, we show that urea can accumulate to levels closer to observed values and yet still be independent of the lactate effect on NaCl recycling.
High Pu LDL: We explored the role of Pu LDL in this model using both the baseline parameter set of Table 2 (based on measurements for the rat kidney and also chosen to facilitate comparison with earlier 3-D models) and a parameter set based on values reported for the chinchilla kidney [as reported in Layton et al.], which has an an even higher Pu LDL than the rat.
Subsequent measurement of tubular permeabilities by in vitro microperfusion was in direct conflict with these predictions; e.g., Pu LDL was found to be low in the rabbit, which does not develop a highly concentrated urine, but quite high in species with wellconcentrated urine, such as the chinchilla and the rat .

7 A second lesson for the mammalian system is that prebend enlargements are likely to play a significant role in the outer medullary and inner medullary concentrating mechanisms. Although this role has been previously hypothesized, this study of the quail medullary cone indicates, in the context of a specific physiological setting, that the PBEs can significantly increase concentrating capability. Prebend segments have been identified in the long loops of Henle of the chinchilla; these segments have transport properties (low water permeability and high solute permeabilities) similar to thin ALs in chinchilla. PBEs have been reported in long loops in rats. Short loops of Henle in rat have recently been found to have a long prebend segment that appears to be water impermeable but urea permeable. This segment, which is coextensive with the inner part of the inner stripe of the outer medulla, has been hypothesized to play a role in urea cycling, but it may also enhance concentrating capacity by removing the osmotic load that would otherwise be presented to the inner stripe by DL fluid.

8 Structural identification of DTL-type and ATL-type segments of single thin limbs of Henle’s loop in the inner medulla. Rat inner medullary DTL were differentiated from ATL on the basis of structural characteristics when viewed with a compound microscope equipped with Nomarski DIC optics. The cells of the DTL with their nuclei appearing to bulge into the lumen create a distinct luminal outline. The cells of the ATL appear flatter than those of the DTL and exhibit dominating, round nuclei. A distinct luminal outline is absent in the ATL. These structural characteristics closely resemble those previously reported for the chinchilla thin limbs of the inner medulla. When first beginning to tease out thin limbs, we made certain that the cells we were defining as ‘‘DTLtype’’ based on the work of Chou and Knepper were seen at the beginning of the DTL (following the straight portion of the proximal tubule) and that the cells we were defining as ‘‘ATL-type’’ were seen at the end of the ATL where it joined the thick segment of the ascending limb. In this way, we thought that we could be absolutely certain that segments with these cell types truly represented either DTL or ATL. The reason for this is that we were interested in the papillary thin limbs (those from juxtamedullary nephrons), and it was rarely possible to tease out a whole DTL or ATL.
The presence of a large number of mixed-type thin limbs in Munich-Wistar rat kidneys, along with the presence of mixed-type thin limbs in the kidneys of other species, suggests that they may serve a common and important function in mammals. At present, we can only speculate on their possible significance. In chinchillas and rats (and, we assume, other mammalian species), the water permeability of the DTL is markedly higher than the water permeability of the ATL.

9 Chou y Knepper encontraron que en la chinchilla el grado de permeabilidad hídrica disminuía significativamente en segmentos cercanos al extremo de la papila comparándolos con segmentos de la región externa de la medula interna, y anotaron el rango de permeabilidades de todos los niveles de la medula interna de la chinchilla, incluida la región externa. En la rata, al menos,  la baja permeabilidad hídrica en segmentos de los niveles inferiores de la médula interna es debida aparentemente a la ausencia de expresión de AQP1.

10 The second IM segment, which we call LDL3 and which corresponds to the AQP1-null segment of the DTL, was assumed to be impermeable to NaCl but to have a water permeability of 400 µm/s in the pipe mode, based on micropuncture experiments in rat DTLs from the deep the IM, and to have no water permeability in the SS mode, consistent with our finding of no AQP1 expression and with micropuncture experiments in chinchilla indicating a water permeability of 50 µm/s in DTLs from the deep IM.
In the SS mode, we assumed that all IM loop segments have at least a moderate permeability to urea and that the urea permeabilities of LDL3, the prebend segment, and the ATL are very large. The LDL2S, ATLS, and LDL2 were assigned a permeability of 13 x 10-5 cm/s. The urea permeabilities of the LDL3, the prebend segment, and the ATL were suggested to us by the high permeabilities measured in the long loops of Henle of chinchilla. The permeability of the prebend segment and ATL was taken to be 150 x 10-5 cm/s, lower than the measured value of 170 x 10-5 cm/s in chinchilla ATL, but about an order of magnitude larger than reported values in rat of 14–23 x 10-5 cm/s. The permeability for LDL3 was taken to be 100 x 10-5 cm/s, about twice the value of 48 x 10-5 cm/s reported in chinchilla for the lower DTL. Our value for urea permeability in LDL3 supports the effective function of the SS mode and may not be unreasonable, because results from microperfusion studies of DTLs may have been skewed by tubules that spanned more than one functional segment.
The pipe mode concentrates more effectively when loop of Henle urea permeabilities (in units of 10-5 cm/s) are sufficiently small (≈1–5), whereas the SS mode concentrates more effectively when the loop urea permeabilities are sufficiently large (more than or equal to ≈100); intermediate values (e.g., ≈10–50) significantly decrease concentrating capability in both modes. Because perfused tubule studies have indicated that chinchilla loops are highly permeable to urea, whereas our preliminary data suggest that rat loops are nearly impermeable to urea, both the low and high urea permeability limits (i.e., both the pipe and SS mode) could be exploited in vivo, depending on species. On the other hand, definitive evidence that the loops are only moderately urea permeable when animals are in an antidiuretic state would cast doubt on both modes.
Unlike most other recent model studies, we have not considered our loop of Henle urea permeability choices to be bound by average values reported in perfused tubule experiments; rather, in conformity with our own recent experiments and unpublished preliminary observations, we have assumed low loop of Henle urea permeabilities in AQP1- null loop segments, or, alternatively, we have assumed high urea permeabilities in those segments, similar to values reported in chinchilla. Urea permeabilities obtained in perfused tubule measurements in the rat, hamster, and rabbit have exhibited a large range of variability, and the measurements were obtained under experimental circumstances that may not have been representative of normal function in antidiuretic animals.

 


Bibliografía impresa
  1. Hoefer HL, Crossley DA. Chinchillas. En: Meredith A, Redrobe S. Manual de animales exóticos. 4ª ed. Barcelona: Ediciones S, 2007: 89-104.
  2. Bellamy D, Weir BJ. Urine composition of some hystricomorph rodents confined to metabolism cages. Comp. Biochem. Physiol. 1972; 42A: 759-771.

  3. Recursos en línea

  4. Boussarie D. Carte D'identite Chinchilla. 27 WSAVA Congress. 2002. Consultado el 04 de septiembre de 2007.
  5. Thomas SR. Cycles and separations in a model of the renal medulla. Am. J. Physiol. 275 (Renal Physiol. 44): F671–F690, 1998. Consultado el 13 de septiembre de 2007.
  6. Mejia R, Wade JB. Immunomorphometric study of rat renal inner medulla. Am J Physiol Renal Physiol 282: F553–F557, 2002. Consultado el 13 de septiembre de 2007.
  7. Stéphane H, Thomas SR. Inner medullary lactate production and urine-concentrating mechanism: a flat medullary model. Am J Physiol Renal Physiol 284: F65–F81, 2003. Consultado el 13 de septiembre de 2007.
  8. Layton H E, Davies JM, Casotti G, Braun EJ. Mathematical model of an avian urine concentrating mechanism. Am J Physiol Renal Physiol 279: F1139–F1160, 2000. Consultado el 13 de septiembre de 2007.
  9. Pannabecker TL, Dahlmann A, Brokl OH, and Dantzler WH. Mixed descending- and ascending-type thin limbs of Henle’s loop in mammalian renal inner medulla. Am. J. Physiol. Renal Physiol. 278: F202–F208, 2000. Consultado el 13 de septiembre de 2007.
  10. Pannabecker T L, Abbott DE, Dantzler WH. Three-dimensional functional reconstruction of inner medullary thin limbs of Henle’s loop. Am J Physiol Renal Physiol 286: F38–F45, 2004. Consultado el 13 de septiembre de 2007.
  11. Layton AT, Pannabecker TL, Dantzler WH, Layton HE. Two modes for concentrating urine in rat inner medulla. Am J Physiol Renal Physiol 287: F816–F839, 2004. Consultado el 13 de septiembre de 2007.
  12. McManus JJ. Water relations of the chinchilla Chinchilla lanigera. Comparative Biochemistry and Physiology Part A: Physiology 1972. (41) 3: 445-450. Consultado el 13 de septiembre de 2007.
  13. Gutman Y, Beyth Y. Chinchilla laniger - discrepancy between concentrating ability and kidney structure. Life Sciences 1970. (9) 1: 37-42. Consultado el 13 de septiembre de 2007.
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