DIETER JUNGST~
Mesenteric, hepatic and splanchnic extraction of C-terminal and N-terminal atrial natriuretic factor was investigated in male Sprague-Dawley rats. Plasma concentrations (mean f S.E.M.) of C-terminal atrial natriuretic factor were 55.0 f 6.1 fmouml, 31.2 f 4.0 fmoUml and 23.5 f 3.3 fmol/ml (n = 12) in the abdominal aorta, the portal vein and the hepatic vein, respectively. N-terminal atrial natriuretic factor plasma levels in these vessels were 3031 * 766 fmoUml, 2264 f 661 fmoUml and 1618 f 496 fmol/ml (n = 61, respectively. Although the mesenteric extraction ratio was higher (p < 0.05) for C-terminal atrial natriuretic factor (42% f 6%) than for N-terminal atrial natriuretic factor (28% f 4%), there were no significant differences in the hepatic extraction ratio (41% f 6% vs. 39% f 6%) and the splanchnic extraction ratio (56% k 5% vs. 50% f 7%). These data suggest a major role of the liver in the splanchnic extraction of C-terminal and of N-terminal atrial natriuretic factor in the rat. (HEPA"KOGY 1992;16790-793.) The atrial natriuretic factor (ANF) has been shown to be involved in volume homeostasis (1-7). Furthermore, there is increasing evidence that it may play a role in immune and reproductive functions (8,9). ANF circulates as a 28-amino acid C-terminal fragment and a 98-amino acid N-terminal fragment. Although the C-terminal fragment is known to be the bioactive compound of ANF, the biological role of the N-terminal is not yet clearly established. However, there is evidence of a vasodilatory effect of this fragment after further cleavage in plasma (10).