Figure 1.
Figure 1.

The angiotensin-bradykinin pathways. Angiotensin-converting enzyme (ACE) plays are role in the regulation of the bradykinin and angiotensin pathways. Bradykinin can elicit vasodilation by increasing endothelial derived hyperpolarizing factors (EDHF), prostacyclin (PGI2), or nitric oxide (NO). Angiotensin II will cause vasoconstriction. However, if angiotensin II is further converted to angiotensin 1-7, vasodilation could occur via NO and PGI2.

 


Figure 2.
Figure 2.

Linear regression analysis of gravid uterine artery blood flow with gravid uterine artery resistance index at d 130 of gestation in ewes (n = 31). Data are from Lemley et al. (2013).

 


Figure 3.
Figure 3.

Linear regression analysis of gravid uterine artery resistance index with total placentome weight at d 130 of gestation. Linear regression analysis was only significant in nutrient-restricted ewes (n = 15; data shown) although no significant effects were observed in adequate fed ewes (data not shown). Data are from Lemley et al. (2013).

 


Figure 4.
Figure 4.

Umbilical artery blood flow (BF) throughout gestation in ewes. Blood flow was evaluated at least 1h postfeeding and before lights off (5 h postfeeding). Baseline measurements were taken on d 48 of gestation and treatments commenced on d 50 of gestation. Treatment groups consisted of no melatonin (CON), 5 mg of melatonin (MEL), 100% of NRC recommendations (ADQ), or 60% of NRC recommendations (RES). Figure 3A depicts individual treatment groups. The 3-way interaction of melatonin treatment by nutritional plane by day was not significant (Panel A; P = 0.15). Significant interactions were observed for melatonin treatment by day (Panel B; P < 0.001) and nutritional plane by day (Panel C; P < 0.0001). Asterisks (*) represent differences (P < 0.05) among means within the same time point. From Lemley et al. (2013); published with permission.

 


Figure 5.
Figure 5.

Linear regression analysis of umbilical blood flow with fetal weight at d 130 of gestation in ewes. Linear regression analysis was only significant in no melatonin supplemented ewes (n = 15; data shown) although no significant effects were observed in ewes receiving 5 mg of melatonin per day (data not shown). Data are from Lemley et al. (2013).

 


Figure 6.
Figure 6.

Uterine artery blood flow during late gestation in pregnant beef cows that were fed 100% of NRC requirements (circles) restricted from d 30 to 85 and then realimented to control levels (triangles) or restricted from d 30 to d 140 and then realimented to control levels (squares).