Is cerebral control of plasma [Na] a major determinant for systemic sodium balance?
To evaluate the role of volume expansion for prandial/postprandial natriuresis, we first determined spontaneous daily NaCl, H2O, and diet turnover and Evans blue and inulin spaces in male Wistar rats on various high-salt diets. Second, we measured the time course of Na and water clearance in chloralose/ketamine anesthetized rats over 270 minutes after a single intragastric Na load (0, 290.4, or 581 micromol/100 g body weight). Finally, similar measurements were made during and after a local [NaCl] increase in the left carotid artery supplying the brain for 60 minutes. Daily NaCl, H2O, and diet intake per rat was 2 to 74 mmol, 13 to 223 ml, and 1.5 to 33 g, respectively. Only inulin space and plasma [Na] correlated with daily Na uptake (X; regressions Y = 0.02X + 15.13, N = 99, r2 = 0.0716, P = 0.02; and Y = 141.7 + 0.1005X, N = 179, r2 = 0.104, P < 0.0001, respectively). Under chloralose/ketamine anesthesia, 86% to 102% of the total (i.v. plus i.g.) Na load and some 50% of the unilaterally administered intracarotid Na were excreted. Chloralose/ketamine anesthesia is thus suitable for studies on Na balance mechanisms. Plasma [Na] is under cerebral control. Because of its immediate onset, this mechanism might be the principal determinant of prandial and postprandial natriuresis and hence for the systemic Na balance.
Häberle
D A
DA
Department of Physiology, University of Munich, Germany. u7232aa@sunmail.lrz-muenchen.de
Biller
W
W
Ise
T
T
Metz
C J
CJ
D000818:Animals; D001794:Blood Pressure; D001921:Brain / Q000502:physiology*; D002339:Carotid Arteries; D006400:Hematocrit; D007269:Injections, Intra-Arterial; D007668:Kidney / Q000294:innervation* / Q000502:physiology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012982:Sodium, Dietary / Q000097:blood* / Q000652:urine; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
D012982:Sodium, Dietary