Cardiovascular Responsiveness to Arginine Vasopressin in Water‐loaded and Sodium‐depleted Pregnant and Non‐pregnant Sheep

Abstract

1. In conscious ewes pregnancy was associated with a significantly increased heart rate and cardiac output, while mean arterial pressure (MAP) and stroke volume were unchanged. 2. The present study examines the effect of arginine vasopressin (AVP) infused at 0.3, 1, 3.0, and 10 micrograms/h, into water-loaded and sodium-depleted ewes, either non-pregnant or during the last third of gestation. 3. In the water-loaded state, MAP rose significantly at the lowest rate of infusion in both pregnant and non-pregnant ewes. Bradycardia occurred first at 0.3 micrograms/h in the pregnant ewes but not until 3.0 micrograms/h in the non-pregnant animals. 4. In sodium deficiency there was no increase in MAP at any rate of infusion in either group. Bradycardia occurred in both groups at 1 microgram/h. 5. This study shows that the pressor effects of AVP are unchanged by pregnancy. However, pregnant ewes are more sensitive to AVP-induced bradycardia when the ewes are water-loaded.

Water movements after an intraruminal water load in pregnant and lactating Sardi sheep

“…Before the water load, total plasma protein was lowered during both pregnancy and lactation, while plasma osmolality was similar during pregnancy, lactation and the control period ( In agreement with previous observations in goats (Olsson et al, 1982) (Benlamlih, 1984) and fast plasma clearance rate for the argininevasopressin (Wintour et al, 1987 (Engelhardt, 1970). On the other hand, rumen osmolality was the same during pregnancy, lactation and the control period, and therefore, the net water absorption from the rumen caused by the osmotic gradient was probably the same during all 3 physiological states.…”