| Abstract: | To investigate the influence of acute isotonic volume expansion (VE) on the plasma concentration of atrial natriuretic factor (ANF), the excretion of catechol compounds and electrolytes and the whole kidney glomerular filtration rate (GFR), these variables were measured before and during 60 min of VE (2% of body weight per hour). Atrial natriuretic factor was measured at the end of the experiment. In a control group (n= 7) without volume expansion, plasma ANF was 58 ± 4 pg ml-1. The excretion of sodium, dopamine (DA), 3 ,4–dihydroxyphenylacetic acid (DOPAC), noradrenaline (NA) and GFR did not change during the control study. In VE animals (n= 7) plasma ANF was 82 ± 7pg ml-1, significantly higher than in the control group. Sodium excretion increased more than 17–fold. The excretion of the DA increased by 38% and that of DOPAC by 30%. Noradrenaline excretion remained unchanged while GFR increased by 20%. In haloperidol-pretreated animals subjected to VE (n = 7). plasma ANF was 81± 8 pg ml-1 during VE, significantly higher than in the control animals. Although the sodium excretion increased more than ninefold in this group during VE, this increase was only 55 % of that in the VE group not given haloperidol. The DA and DOPAC excretion was increased by haloperidol, indicating a feedback effect of receptor blockade. DOPAC excretion was not increased further by VE, hut the excretion of DA increased by 15% and GFR increased by 19%. In conclusion, haloperidol reduced the natriuretic response to VE without impairing either the VE-induced release of ANF or the increase in GFR. The results indicate an important involvement of ANF and DA in the natriuretic response to VE. |
