Blood flow and progesterone levels in the ovary of cycling and pregnant pigs

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Abstract
Blood flow to the ovaries, uterine horns and other organs of the adult pig was determined by using radioactive indicator 86RbCl. The validity of the indicator technique was established in the immature pig. Blood flow in the ovary and uterine horns was determined in non-pregnant animals on the 10th, 12th, 14th, and 16th days of estrous cycle and in pregnant animals on the 10th, 12th, 14th, and 16th days after mating. The pregnant animals were divided into 2 groups, those with a unilaterally gravid uterus (pregnant I) and those with a bilaterally gravid uterus (pregnant II). Half of the nongravid uterine horn in pregnant I animals was removed, leaving intact the portion adjacent to the uterine tube. Blood flow (ml/(min.X g)) to the luteal tissue was similar in pregnant and nonpregnant animals. Corpora lutea weight and luteal progesterone concentration, however, decreased by day 16 in nonpregnant pigs and in the ovary ipsilateral to the nongravid horn in one animal in group pregnant I. Luteal blood flow (ml/(min. X corpus luteum)) decreased by day 16 in pregnant and nonpregnant animals. Blood flow (ml/(min. X g)) was similar in pregnant and nonpregnant animals between days 10 and 16 in ovaries minus corpora lutea and in the uterine horns. These results indicate that decrease in blood flow does not precede the initiation of luteal regression in the pig.