Potassium: Aldosterone relationships in pregnant ewes and chronically cannulated ovine fetuses

Abstract

As maternal hyperkalemia quickly induces fetal hyperkalemia, it was decided to investigate the effect of small elevations of plasma [K+] on the peripheral blood aldosterone concentration in chronically catheterized ovine fetuses and to compare this response to that obtained in the adult ewe both pregnant and nonpregnant. For elevations of plasma [K+] of 0.1 to 0.3 mmole/ liter blood aldosterone concentrations were elevated by 6.7 ± 4.9 (9) ng/dl in nonpregnant sheep, 6.3 ± 5.0 (6) in pregnant ewes, but only 0.3 ± 1.7 (4) in fetal sheep. For increments in plasma [K+] of 0.4 - 1.0 mmole/liter aldosterone increments in nonpregnant ewes were 9.5 ± 4.5 (4) ng/dl compared with 10.1 ± 4.7 (5) in pregnant ewes and 1.5 ± 2.6 (7) in fetuses. There was no obvious correlation between the age of the fetus and the response to increased plasma [K+]. In effect, the blood aldosterone concentration of the fetus was not elevated by increasing plasma [K+]. © 1979 International Pediatric Research Foundation, Inc.