Clinical syndromes associated with disorders of renal tubular chloride transport: excess and deficiency of a circulating factor?

Control of vascular tone in the syndromes of Bartter and Gitelman

Bartter's and Gitelman's syndromes can be used as models to gain insight into the mechanisms responsible for maintaining/controlling vascular tone. In fact, the study of patients with these syndromes provides important insights into mechanistic details of the most relevant pathways of vascular tone. So far, several experimental findings in patients with these syndromes point to G protein abnormalities and suggest that the intracellular signaling systems that involve the G protein complex transducing components may be defective, leading to altered vascular reactivity. These results are also of particular interest because the derangements found in Bartter's and Gitelman's syndromes are the mirror images of those involved in the pathophysiology of hypertension.

Renal function during bovine neurotensin infusion in man

The peptide hormone neurotensin (NT) is found mainly in gut endocrine cells of the ileum, but has also been identified as a putative neurotransmitter in the central and peripheral nervous systems. It may have a dual role as a circulating gastrointestinal hormone and peripheral neurotransmitter. Its predominant effects are to reduce oesophageal sphincter tone, inhibit gastric secretion and emptying and inhibit intestinal motility, but stimulate intestinal and pancreatic exocrine secretion; NT-like immunoreactivity has been found in kidney and therefore NT may influence renal function. When infused i.v. in rabbits it causes antinatriuresis. We have studied its renal effects in 11 healthy males by i.v. infusion under conditions of altered dietary sodium. Postprandial circulating neurotensin levels were reproduced by infusion. There were no consistent systemic or renal haemodynamic effects. Plasma electrolytes and renin did not change. Only renal chloride excretion changed significantly, falling by ca. 30%, and recovering after infusion. There is no evidence for a specific renal tubular chloride transport mechanism, but coupled cotransport, Na+:K+:2CI-, may be hormonally regulated. NT might stimulate this process and contribute to the renal response to changes in dietary composition, especially sodium intake.