Effect of urodilatin on cGMP accumulation in the kidney

Urodilatin is found in the urine and is thought to be produced in the kidney. The effect of urodilatin on cGMP accumulation in the kidney was investigated. cGMP accumulation by urodilatin and atrial natriuretic peptide (ANP) were compared with tubule suspensions from renal cortex, outer medulla, inner medulla, and microdissected nephron segments. Urodilatin-stimulated cGMP accumulation was higher in tubule suspensions from the inner medulla than in those from the cortex and outer medulla. The highest accumulation stimulated by 10(-6) M urodilatin among nephron segments was observed in glomeruli and inner medullary collecting ducts (IMCD). Small accumulations were seen in proximal convoluted tubules and medullary thick ascending limbs. Urodilatin-stimulated cGMP accumulation was almost equal to that stimulated by the same concentrations of ANP in these nephron segments. Urodilatin (10(-8) M) did not stimulate cGMP accumulation in glomeruli, but it stimulated cGMP accumulation in IMCD by threefold. This pattern was quite similar to that with ANP. It was concluded that urodilatin has a similar ability to ANP in stimulating cGMP synthesis and that the main target sites are glomeruli and IMCD.