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 α-keto-δ-guanidinovaleric acid (α-keto-δ-GVA), guanidinosuccinic acid (GSA), creatinine (CTN), γ-guanidinobutyric acid (γ-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 α-keto-δ-GVA, γ-GBA, α-N-acetyl-arginine and homoarginine remained unchanged. In contrast, GSA, guanidinoacetic acid (GAA), creatine (CT), CTN and β-guanidinopropionic acid (β-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 β-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.