A primary renal alteration due to a genetic polymorphism of the cytoskeletal protein adducin associated with an up-regulation of the renal Na-K pump and increased levels of ouabainlike factor (OLF) has been identified as a possible causes of hypertension in Milan rats (MHS). This adducin polymorphism has also been found to be associated with hypertension and the blood pressure changes related to renal Na handling in humans and increased OLF levels have been found in a relevant portion of hypertensive patients. Increased activity and expression of the Na-K pump has also been observed under the following in vitro'and `in vivo' conditions: rat renal cells transfected with the `hypertensive' variant of adducin, as compared with normal cells; normal rat renal cells incubated for 5 days with 10_9 M ouabain and normal rats made hypertensive by a chronic infusion of low doses of ouabain (OS rats). An up-regulation of the Na-K pump seems therefore to be a common biochemical alteration induced both by an adducin polymorphism and/or chronic exposure to low concentrations of ouabain (or OLF). A new antihypertensive compound, PST 2238, that selectively antagonizes the pressor effect and the alteration of the renal Na-K pump induced both by an adducin polymorphism and OLF, is described. The ability of PST 2238 to lower blood pressure and normalize the Na-K pump both in MHS and OS rats suggests that this compound could be useful in the treatment of those forms of essential hypertension in which renal Na-handling alterations are associated with either adducin polymorphisms and/or increased OLF levels.(Hypertens Res 2000; 23 Suppl: S15-S19) Key Words: hypertension, adducin, ouabainlike factor, therapy, pharmacogenomic
IntroductionEssential hypertension is a complex disease in which many genetic and environmental factors interact to result in a final blood pressure increase and the risk to develop specific organ complications (mainly at the cardiac, renal, and brain levels) (1, 2). Although the antihypertensive efficacy of different classes of drugs is widely recognized and is similar when large populations are compared, there is much individual variability in the response to a given therapeutical regimen (3). Population surveys have demonstrated that less than 30% of patients are adequately treated. These problems arise primarily from the lack of a complete understanding of the mechanisms that underlay the development of primary hypertension and its organ complications. Therefore, the success of a future new therapy for hypertension will depend upon our understanding of the molecular-genetic mechanisms operating in a subset of patients and the ability of the new drug to correct such a mechanism. A pharmacogenomic approach (4, 5) has been adopted by Prassis sigma-tau to develop a new class of antihypertensive compounds able to lower blood pressure by correcting a specific genetic-molecular mechanism previously demonstrated to be involved both in rat and human hypertension. As a consequence, the