Dietary sodium manipulation and vascular responsiveness during pregnancy in the rabbit

The interrelationship of sodium intake and blood pressure regulation during pregnancy is not clear. The effects of dietary sodium loading and restriction on plasma levels of catecholamines, mean arterial pressure, and vascular response to two pressor agents, Levophed and angiotensin II, were investigated in 49 chronically prepared primigravid rabbits. Sodium loading increased mean arterial pressure (p less than 0.005), but did not alter the response to either pressor agent. Sodium restriction did not alter mean arterial pressure, but did increase plasma norepinephrine (p less than 0.05) and epinephrine (p less than 0.02). Negative correlations between plasma levels of norepinephrine and vascular response to infusions of both pressor agents were observed during sodium restriction, -0.61 (p less than 0.05) for angiotensin II, and -0.74 (p less than 0.05) for norepinephrine. A similar correlation of -0.81 (p less than 0.05) was observed for angiotensin II in control animals. Norepinephrine appears to play a significant role in blood pressure maintenance and vascular response in pregnancy. This role is enhanced during sodium restriction.