GENE-EXPRESSION OF CENTRAL AND PERIPHERAL RENIN-ANGIOTENSIN SYSTEM COMPONENTS UPON DIETARY-SODIUM INTAKE IN RATS

The effects of dietary sodium intake on the gene expression of the ren in-angiotensin system (RAS) were investigated in rat central and perip heral tissues in a single set of experiment. Northern and reverse tran scriptase-polymerase chain reaction (RT-PCR) techniques were used to d etect mRNA expression in rats fed a low- or a high-sodium diet (5 or 5 00 mmol Na+/kg diet) for 20 days. Plasma and renal renin levels were e levated in rats maintained on the low-sodium diet. Sodium deprivation enhanced the expression of angiotensinogen, renin, AT(1A) and AT(1B) r eceptor subtypes in the hypothalamus, but suppressed them in the brain stem. Kidney and adrenal levels of those mRNAs were also enhanced in t he sodium-restricted rats. Both AT(1A) and AT(1B) mRNAs changed in a s imilar magnitude in each tissue examined upon dietary sodium intake. A T(1A) was the predominant receptor subtype of AT(1) in all the tissues examined in the present study except the adrenal gland. The present s tudy demonstrated that dietary sodium modulated the gene expression of the RAS components in the central and peripheral tissues. It also sho wed that the RAS components in the brainstem and hypothalamus were dif ferentially expressed upon sodium deprivation. This suggests different roles of the RAS in these tissues in maintaining body fluid homeostas is in response to different sodium intakes.