Dehydration modifies guanidino compound concentrations in the different zones of the rat kidney

Abstract

Guanidino compounds (GCs) related to arginine (Arg) are unevenly distributed along the cortico-papillary axis of the rat kidney. Inasmuch as the concentration of alpha-keto-delta-guanidinovaleric acid (alpha-keto-delta-GVA), guanidinosuccinic acid (GSA), creatinine (CTN), gamma-guanidinobutyric acid (gamma-GBA) and methylguanidine (MG) increased steeply along the inner medulla in parallel to the urea and osmotic gradients, the question arose as to whether dehydration enhances their renal content and distribution. To examine this possibility, adult male rats were dehydrated by removing the drinking water for 24 or 48 h. The kidneys were sliced and cut in seven sections along the cortico-papillary axis. Twelve GCs were determined by liquid chromatography in each renal zone. Dehydration modified GC concentrations and regional distribution. The renal content of Arg, guanidine and MG was decreased while that of alpha-keto-delta-GVA, gamma-GBA, alpha- N-acetyl-arginine and homoarginine remained unchanged. In contrast, GSA, guanidinoacetic acid (GAA), creatine (CT), CTN and beta-guanidinopropionic acid (beta-GPA) concentrations were enhanced significantly in different renal zones after 24 and 48 h dehydration. In addition, the tissue level of GCs supplying energy, such as CT and beta-GPA, the precursor of CT (GAA) and its metabolite (CTN) were enhanced under dehydration. Arg and CT account for 80-90% of the GCs located in the renal cortex. Variations of some GC levels under dehydration may modify enzyme activities, renal metabolism and cell function.

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“…Abundance of 4-guanidinobutanoate was strikingly decreased ( Figure S1A ) and was the most important feature contributing to the clustering of groups in the PLS-DA analysis ( Figure S1B ). Guanidino compounds are metabolized from arginine, and dehydration modifies abundance of these compounds in the kidney [ 25 ]. Kidney injury not only results in reduced arginine synthesis but change in levels of guanidino compounds and their metabolism in muscles and liver [ 26 ].…”

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“…The blood contained in each kidney was removed with blotting paper (blood-free). Each kidney was sliced longitudinally with a razor blade and cut into 7 zones at 4°C under a stereomicroscope as follows : cortex (C); outer stripe of the outer medulla (OS); inner stripe of the outer medulla (IS); inner medulla (IM), which was subdivided into 2 equivalent portions (IM1 and IM2); and papilla, which was also subdivided into 2 equivalent portions (Pap1 and Pap2), as published earlier [11]. Pieces of C, OS, and IS were collected from each rat to determine the levels of each GC.…”

“…The gradient of these 2 solutes is deeply affected in response to antidiuresis and diuresis [2,9,10]. Recently, we established that water deprivation for 24 and 48 hours was associated with an increase of the renal content of GSA, GAA, CT, CTN, and β-GPA along the corticopapillary axis in parallel with these 2 gradients [11]. In contrast, the renal content of Arg, G, and MG was decreased after 1 and 2 days of water deprivation.…”

“…Arterial blood was collected in 36 rats, and the 2 kidneys of 3 groups of 10 rats were collected to dissect the 7 well-defined renal zones as previously published [2,11].…”