The relationship of changes in mammary blood flow and plasma progesterone at the time of parturition in the ewe.
Previous studies indicate that there is a fall in maternal plasma progesterone and a marked increase in mammary blood flow (MBF) at the time of parturition in ewes. In this experiment the role of progesterone as a cause of this increase in MBF was investigated. Progesterone was infused (9.9 mcg. per minute) into a branch of the mammary artery in five sheep during the induction of premature labor by fetal dexamethasone infusion (1 mg. per 24 hours) to prevent the normal fall in concentration of local mammary artery progesterone. Five ewes used as controls received a mammary artery infusion of cholesterol (9.9 mcg. per minute). In the cholesterol-infused group MBF increased significantly from baseline after 13 +/- 4 hours (mean +/- standard error) to a peak flow of 235 +/- 9 ml. per minute. In the group receiving the progesterone the increase in MBF was delayed to 35 +/- 7 hours, reaching only 161 +/- 22 ml. per minute. These results were significantly different from control group results (p less than 0.01). This study suggests that the fall in maternal plasma progesterone which occurs at the time of parturition may play a role in the increase in MBF that occurs prior to the onset of labor, delivery, and lactogenesis.
D000818:Animals; D005260:Female; D007751:Labor, Induced; D008321:Mammary Glands, Animal / Q000098:blood supply*; D011247:Pregnancy; D011374:Progesterone / Q000097:blood* / Q000494:pharmacology; D012039:Regional Blood Flow; D012756:Sheep
D011374:Progesterone