We investigated the temporal association between placental vascular endothelial growth factor (VEGF), a potent stimulator of angiogenesis and vascular permeability, and changes in placental/endometrial vascularity on selected days throughout gestation in the pig. Placental and endometrial tissues were collected from sows on Days 25 (n = 4), 36 (n =6), 44 (n =6), 70 (n =5), 90 (n =5), and 112 (n =7) of gestation. Cross sections of the placental/endometrial interface of each conceptus were used to estimate the number of blood vessels per unit area via image analysis and the intensity of VEGF staining via immunohistochemistry. Placental tissues were also collected on these days to evaluate VEGF mRNA expression. Placental VEGF mRNA expression and the numbers of blood vessels per unit area of placental and adjacent endometrial tissue were low and decreasing from Day 25 to Day 44, before increasing (P < 0.05) markedly and progressively through Day 112. These data are consistent with the marked increase in VEGF immunostaining in the chorionic and uterine luminal epithelium from early to late gestation. Further, these increases in placental VEGF mRNA were positively correlated with fetal weight (r = 0.73; P < 0.0001) and placental efficiency (fetal weight/placental weight ratio; r = 0.66, P < 0.0001). These data are consistent with a role for VEGF in increasing the number of blood vessels at the placental endometrial interface, resulting in an increased capacity for nutrient transfer from the maternal to the fetal compartment.
The vasoconstrictor activity of the ovarian vascular bed in vitro was investigated during the oestrous cycle and early pregnancy. Gilts were killed during the follicular phase (Days 20 to +1; N = 5) or luteal phase (Days 11 to 13; N = 4) of the oestrous cycle, or on Day 13 of pregnancy (N = 5). Immediately before death, a sample of vena cava blood was obtained for determination of progesterone and oestrogen (oestrone and oestradiol-17 beta) concentrations. One ovary was removed, cannulated, perfused in vitro, and subjected to 10-min infusions of saline (vehicle control) and noradrenaline. Vasoconstriction was provoked by electrical stimulation at the end of each infusion. Ovaries from luteal-phase gilts exhibited greater (P less than 0.01) vasoconstriction than did ovaries from follicular-phase and pregnant gilts at the end of saline and noradrenaline infusions. The oestrogen to progesterone ratio was less (P less than 0.01) for luteal-phase and pregnant than for follicular-phase gilts. Vasoconstriction was negatively correlated (r = -0.99, P less than 0.01) with the oestrogen to progesterone ratio in systemic blood of gilts during the oestrous cycle but not during early pregnancy (r = +0.39, P greater than 0.10), possibly due to an effect of the conceptuses.
Pregnant cows were fed pine needles (PN, 2 kg.cow−1.d−1) mixed with the diet to determine factors that affect abortion response. In Exp. 1, treatments were used to determine the effects of experimental stress and pelleting of pine needles. Pelleting needles and experimental stress delayed abortion response (P < .01). Stress-induced delay was associated with abnormal patterns of progesterone and cortisol (P < .01). In Exp. 2A and 2B, the role of the corpus luteum (CL) in abortion response to PN consumption was investigated by regressing the CL with prostaglandin F2α. Regression of the CL and PN feeding reduced interval to parturition, but the effect of PN feeding was less when the CL was regressed (PN × CL, P < .01). The progesterone increase in response to experimental stress was decreased by CL regression (P < .01). In Exp. 3, melengestrol acetate (MGA) was fed (0, 2, or 4 mg.cow−1.d2212;1) in addition to PN. Parturition was blocked more effectively as dose of MGA increased (P = .075), but only parturition was blocked rather than the effects of PN. In Exp. 4, CL regression was blocked by feeding ketoprofen. Ketoprofen delayed response to PN, but the effect was only temporary (P < .01). Our conclusions are that 1) experimental stress delays abortion response to PN by increased concentrations of progesterone, 2) pelleting PN decreases their abortifacient activity, and 3) abortions caused by PN can be blocked by feeding a progestin or a prostaglandin inhibitor, but these compounds do not block the primary abortifacient effects of PN.
This study was conducted to define further the role of catechol estrogens (CE) as intermediates in estrogen-stimulated uterine hyperemia. Previous studies from our laboratory strongly suggest that changes in uterine blood flow (UBF) result from alterations in uterine arterial tone (distensibility) and/or contractility (reactivity to α 1-adrenergic agonists). Tone changes appear to set the baseline rate of flow, whereas contractility changes result in short-term reductions in luminal diameter. Changes in uterine arterial tone and contractility result from alterations in Ca2+ uptake through potential-sensitive channels (PSCs) and receptor-operated channels (ROCs), respectively. Uterine and mesenteric arteries were removed from 6 gilts at estrus (Day 0), 9 gilts on Day 13 of gestation (high estrogen, high UBF), and 8 gilts on Day 13 of the estrous cycle (low estrogen, low UBF). Arterial measurements included initial tone (baseline perfusion pressure [BPP] to a constant intraluminal flow) and increased tone after exposure to KCl, the contractility in response to the α 1-agonist phenylephrine, and specific uptake of 45Ca before and after exposure to the CE 4-hydroxylated estradiol (4OH-E2). Contractility of uterine arteries from Day 13 nonpregnant (NP) and Day 13 pregnant (P) gilts to phenylephrine were similar and significantly greater (p<0.01) than contractility of vessels from estrous gilts. The BPP and responses of uterine arteries from Day 13 NP gilts to KCl were greater (p<0.05) than the BPP and responses of arteries from Day 13 P and estrous gilts, which were similar to each other. In addition, 40H-E2 reduced 45Ca uptake by uterine arterial segments from Day 13 NPgilts to levels similar to those determined for vessels from Day 13 P or estrous gilts. These data suggest that increased UBF accompanying either ovarian (estrus) or conceptus (Day 13 P) production of estrogens may result from
Uterine blood flow (UBF) of 6 sows was monitored throughout an estrous cycle and the first 30 days of pregnancy using electromagnetic blood flow probes. Probes were placed around both uterine arteries of each sow on Day 12, 13 or 14 of the estrous cycle (first day of estrus = Day 0). The UBF (ml/min) was recorded twice daily for 15 min at 0700 and 1600 h. Values were averaged over both 15 min periods on each day for each artery and considered an estimate of UBF. Blood flow to uteri of nonpregnant sows was highest from Day −5 to estrus and this was followed by a gradual decline during the remainder of the estrous cycle. The pattern of blood flow to uteri of the sows during early pregnancy was similar to that observed during the previous estrous cycle until Day 11 after mating. On Days 12 and 13 of pregnancy, UBF increased (P<0.0l) 3-fold to 4-fold. No corresponding increase in UBF was observed in nonpregnant sows during this 2 day period. By Day 14 of pregnancy, UBF had returned to a level slightly higher than that observed on Day 11, remained relatively constant from Day 14 to 19, then increased (P<0.01) dramatically to Day 30. a second study was conducted using 7 sows made unilaterally pregnant on day 2 postmating (first day of mating = day 0). fertilized ova were flushed from one oviduct and the ipsilateral uterine horn was ligated at the uterine body with silk sutures (nongravid horn). blood flow probes were placed around both uterine arteries and ubf was recorded twice daily. sows were slaughtered on day 16 postmating. five of the 7 sows had embryos and/or embryonic tissue in the nonligated uterine horn (gravid horn) at slaughter. sows in which embryonic tissue was found had higher (p<0.05) blood flow to the gravid compared with the nongravid uterine horn on days 12 and 13 of pregnancy. corpora lutea on the ovary ipsilateral to a gravid uterine horn had higher (p<0.05) progesterone concentrations (±sem) than did corpora lutea on the contralateral ovary (5.45 ± 1.69 vs 2.07 ± 0.49 µg/g luteal tissue).
Maternal obesity (MO) is associated with offspring cardiometabolic diseases that are hypothesized to be partly mediated by glucocorticoids. Therefore, we aimed to study fetal endothelial glucocorticoid sensitivity in an ovine model of MO. Rambouillet/Columbia ewes were fed either 100% (control) or 150% (MO) National Research Council recommendations from 60 d before mating until near-term (135 days gestation). Sheep umbilical vein and artery endothelial cells (ShUVECs and ShUAECs) were used to study glucocorticoid receptor (GR) expression and function in vitro. Dexamethasone dose–response studies of gene expression, activation of a glucocorticoid response element (GRE)-dependent luciferase reporter vector, and cytosolic/nuclear GR translocation were used to assess GR homeostasis. MO significantly increased basal GR protein levels in both ShUVECs and ShUAECs. Increased GR protein levels did not result in increased dexamethasone sensitivity in the regulation of key endothelial gene expression such as endothelial nitric oxide synthase, plasminogen activator inhibitor 1, vascular endothelial growth factor, or intercellular adhesion molecule 1. In ShUVECs, MO increased GRE-dependent transactivation and FKBP prolyl isomerase 5 (FKBP5) expression. ShUAECs showed generalized glucocorticoid resistance in both dietary groups. Finally, we found that ShUVECs were less sensitive to dexamethasone-induced activation of GR than human umbilical vein endothelial cells (HUVECs). These findings suggest that MO-mediated effects in the offspring endothelium could be further mediated by dysregulation of GR homeostasis in humans as compared with sheep.
