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.