Pressure-dependent renin release: effects of sodium intake and changes of total body sodium

The impact of sodium intake and changes in total body sodium (TBS) for the setting of pressure-dependent renin release (PDRR) was studied in freely mo ving dogs. An aortic cuff allowed servo control of renal perfusion pressure (RPP) at preset values. Protocols were 1) high sodium intake (HSI), 2) low sodium intake (LSI), 3)TBS moderately increased (+3.1 mmol Na/kg body wt) by 20% reduction of RPP for 2-4 days, 4) large increase of TBS (+8.2) by co mbining protocol 3 with aldosterone infusion, and 5) TBS reduced (-3.1) by peritoneal dialyses. Twenty-four-hour time courses of arterial plasma renin activity (PRA) revealed that LSI increased PRA for the first 10 h only; af terward PRA did not differ between LSI and HSI. Reduced TBS increased PRA c onstantly, and the large increase of TBS constantly reduced PRA. PDRR stimu lus-response curves (assessed 20 h after last sodium intake) revealed an ex ponential relationship in each protocol. PDRR was not changed by different sodium intake. Conversely, reduced TBS increased PDRR markedly, whereas the large increase of TBS suppressed it. Thus an inverse relationship between TBS and PRA, i.e., a TBS-dependent renin release, was found. This relations hip was enhanced by decreasing RPP This interplay between TBS-dependent ren in release and PDRR allows the organism a differentiated reaction to change s in TBS and arterial pressure.