Blood Flow to the Uterine and Ovarian Vascular Beds of Gilts During the Estrous Cycle or Early Pregnancy1

Blood flow to uteri, ovaries and other selected maternal tissues of 3 nonpregnant (NP) and 4 pregnant (P) gilts was determined on Days 9, 11, 13 and 15 post-estrus or post-mating (Day 0=first day of estrus or mating) using gamma-labeled microspheres. On either Day 6, 7 or 8, catheters were inserted into the left ventricle and the left femoral artery for infusion of microspheres and simultaneous withdrawal of blood, respectively. At random, 7 × 106 25 μm spheres with one of 4 gamma labels (51Cr, 25Sr, 141Ce or 169yb), in a volume of 10 ml, were infused on each of Days 9, 11, 13 and 15 such that each gilt received all 4 isotopes. Nonpregnant gills were sacrificed on Day 15 and P gills were sacrificed on Day 18. Each uterine horn from NP gifts was divided into 10 sections of equal length and their position in the uterine horn noted. Uteri of P gilts were divided into sections in contact with and devoid of conceptus tissue. Each section of uterus, as well as the cervix, vagina, liver, kidneys, lungs, and fibularis tertius muscles were weighed, homogenized and aliquoted prior to determination of radioactivity. Corpora lutea (CL), and the extraluteal component of each ovary, utero-ovarian lymph nodes, oviducts and the pituitary were weighed and placed directly into vials for counting. Blood flow (EF; ml/mm per g of tissue) to uterine segments was greater (P<0.05) in P than NP gifts on each of the days measured. In P gilts, BF to uterine segments was higher (P<0.05) on Days 11 and 13 than Days 9 and 15 (2.05 ± 0.11 and 1.92 ± 0.10 vs. 1.18 ± 0.05 and 1.48 ± 0.06, respectively). On Day 13, BF to uterine segments in contact with conceptusea was elevated (P<0.01) compared to segments between conceptuses (2.13 ± 0.04 vs. 1.76 ± 0.04). Corpora lutea BF was elevated (P<0.01) in P gilts on Day 13 (23.97 ± 2.51) compared to P gilts on Days 9, 11 or 15 (15.01 ± 1.26) or NP gilts across all Days (15.20 ± 1.21). These data demonstrate that by Day 13 of gestation, uterine segments in contact with conceptuses have greater blood flow than segments between conceptuses. In addition, this conceptus-associated increase in uterine BF on Day 13 occurs concomitantly with a transient rise in BF through the CL.