Hepatic steroid inactivating enzymes, hepatic portal blood flow and corpus luteum blood perfusion in cattle.

Production from the corpus luteum (CL) and/or hepatic steroid inactivation impacts peripheral concentrations of P4, which can alter reproductive performance. Our primary objective was to examine hepatic steroid inactivating enzymes, portal blood flow, and luteal blood perfusion at 10 days post-insemination in pregnant versus non-pregnant beef and dairy cows. Twenty early lactation Holstein cows and 20 lactating commercial beef cows were utilized for this study. At day 10 post-insemination, hepatic portal blood flow and CL blood perfusion were measured via Doppler ultrasonography. Liver biopsies were collected and frozen for later determination of cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A), uridine diphosphate-glucuronosyltransferase (UGT) and aldo-keto reductase 1C (AKR1C) activities. Pregnancy was determined at day 30 post-insemination and treatment groups were retrospectively assigned as pregnant or non-pregnant. Data were analyzed using the mixed procedure of SAS. Steroid metabolizing enzyme activity was not different (p > .10) between pregnant versus non-pregnant beef or dairy cows. Hepatic portal blood flow tended (p < .10) to be increased in pregnant versus non-pregnant dairy cows. Luteal blood perfusion was increased (p < .05) in pregnant versus non-pregnant dairy cows. Pregnant dairy cows appear to have an increased rate of hepatic clearance of P4 in combination with increased synthesis from the CL. This could account for the lack of difference in peripheral P4 concentrations between pregnant and non-pregnant dairy cows. This study highlights the relevance of further investigation into steroid secretion and inactivation and their impact on the maintenance of pregnancy in cattle.

Endometrial blood perfusion as assessed using a novel laser Doppler technique in Angus cows.

Previous studies have characterized ovarian steroid synthesis which directly affects uterine environment and blood flow. Clearance of steroids occurs primarily in hepatic tissues, however, it was discovered that there is an abundant activity of the phase II steroid metabolizing enzyme UDP-glucuronosyltransferase (UGT) in uterine biopsies. No minimally invasive techniques for collecting endometrial perfusion, which is affected by steroids and indicative of reproductive health, have been developed for livestock. The objective of the present study was to characterize UGT activity and endometrial blood perfusion during a normal estrous cycle of cattle. It was hypothesized that there would be increased steroid metabolism during the luteal phase of the estrous cycle and in the uterine horn ipsilateral to the corpus luteum (CL). During the first synchronized estrous cycle, progesterone and UGT activity increased on Day 6 compared with 0 and 3, with the first day of estrus being considered Day 0 of the study. Endometrial perfusion was greater ipsilateral to the CL compared with contralateral on Day 12, and was less ipsilateral to the CL compared with contralateral on Day 18. Similar to perfusion results, nitric oxide metabolites (nitrites) were greatest in the endometrium ipsilateral as compared with contralateral to the CL. Moreover, there was a positive correlation (r = 0.28; P = .04) between endometrial perfusion and nitrite concentration. It is concluded that activity of UGT within the endometrium is affected by the contralateral or ipsilateral location of the CL, and collection of endometrial perfusion data using a laser Doppler probe could be a viable measurement technique as indicated by associated nitrite concentrations in the present study.

Effects of body condition score (BCS) on steroid- and eicosanoid-metabolizing enzyme activity in various mare tissues during winter anoestrus.

The objective of this study was to determine the activity of steroid- and eicosanoid-metabolizing enzymes in horses with varying BCSs. The BCSs of twenty non-pregnant, anoestrous mares were determined prior to euthanasia, and tissue samples were collected from the liver, kidney, adrenal gland, ovary and endometrium. Cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A) and uridine 5'-diphospho-glucuronosyltransferase (UGT) activities were determined using luminogenic substrates. The MIXED procedure of SAS was used to test the effect of BCS on enzyme activity and differences between tissues. Activity of CYP1A in adrenals was increased (p ≤ .05) in BCS 5 versus BCSs 4 and 6. Activity of CYP1A in the liver was increased (p = .05) in BCS 4 versus BCSs 5 and 6. Activity of CYP1A was 100-fold greater (p < .0001) in the liver than in the adrenal, ovary and kidney. Activity of CYP2C was 100-fold greater (p < .0001) in the liver than in the adrenal, ovary and endometrium. Activity of CYP3A was only detectable in the liver. Activity of UGT in the kidney was decreased (p = .02) in BCS 4 versus BCSs 5 and 6. Activity of UGT was threefold greater (p < .0001) in the liver than in the kidney, whereas activity of UGT was ninefold greater (p < .0001) in the kidney than in the ovary and endometrium. In general, BCS did not alter the activity of steroid- and eicosanoid-metabolizing enzymes in horses. However, tissue differences in these enzymes indicated abundant hepatic metabolism in horses, which is similar to other livestock species.

The effect of follicular wave on fertility characteristics in beef cattle.

The objectives of this experiment were to determine the effects of follicular wave (first or second) on diameter of the dominant follicle, concentrations of progesterone and estradiol and the hepatic enzymes that inactivate them, thickness of the endometrium, and pregnancy rates to AI. Beef heifers ( = 101) and cows ( = 106) were randomly assigned to 1 of 2 treatments: insemination to the first follicular wave (FFW) or insemination to the second follicular wave (SFW). Estrous cycles of females were synchronized to ensure appropriate timing for the treatments. The MIXED procedure of SAS was used for analysis. A similar proportion of females in each treatment responded to presynchronization; however, females in the FFW group ovulated in response to the first injection of GnRH of the CO-Synch protocol more frequently. Only females ( = 94) that properly responded to ovulation synchronization were included in further analyses. Cows in the FFW group tended ( 0.06) to have larger ovulatory follicles 36 h post-PGF of the CO-Synch protocol compared to cows in the SFW group (14.22 ± 0.42 and 11.83 ± 0.49, respectively), whereas heifers were similar between treatment groups. Three d prior to AI, circulating concentrations of progesterone were lesser ( 0.01) in females in the FFW (3.63 ± 0.80 ng/mL) than in the SFW (7.12 ± 0.83 ng/mL), whereas concentrations of estradiol tended ( 0.08) to be greater in those in the FFW (82.72 ± 6.48 pg/mL) than in the SFW (65.55 ± 6.74 pg/mL). Concentrations of cytochrome P450 1A in the liver were lesser ( 0.01) in females in the FFW than those in the SFW (0.68 ± 0.08 vs. 0.96 ± 0.06, respectively). Endometrial thicknesses were similar between treatments but were thicker ( < 0.0001) in cows (9.73 ± 0.24 mm) than heifers (7.22 ± 0.26 mm). When considering all females or only those that were properly presynchronized, pregnancy rates were similar between treatments. However, when evaluating females that ovulated to the assigned follicular wave, there was a treatment by parity interaction ( = 0.04) with heifers in the FFW having a lesser pregnancy rate (25.9%) than heifers in the SFW (72.0%) while cows in both treatment groups were intermediate (45.4% in FFW and 50.0% in SFW). The differences in concentrations of steroids between treatment groups may affect fertility of heifers; however, additional research is necessary.

Effects of Supplementing Holstein Heifers with Dietary Melatonin during Late Gestation on Growth and Cardiovascular Measurements of their Offspring.

The objective was to examine the effects of supplementing dams with dietary melatonin during late gestation on offspring growth and cardiovascular measurements. On day 190 of gestation, heifers (n = 20) were blocked by body weight and randomly assigned to one of two dietary treatments consisting of 20 mg of dietary melatonin per day [melatonin (MEL)] or no melatonin supplementation [control (CON)]. Dietary treatments were terminated on day 262 of gestation. At birth, calves were separated from their dams with no further treatments. Calf (n = 18) blood pressure, cortisol, nitrites and total antioxidant capacity were collected on weeks 0, 1, 2, 3 and 4 of age. Calf hepatic portal blood flow and concentrations of insulin-like growth factor 1 were determined on weeks 0 and 4 of age. Calf body weight, abdominal girth, hip height and wither height increased (p < 0.05) with age. An age by treatment interaction (p < 0.01) was observed for calf body weight, which was increased at weeks 8 and 9 of age in calves born to MEL heifers compared to calves born to CON heifers. Pulse pressure, mean arterial pressure, absolute hepatic portal blood flow and blood flow relative to calf body weight were not different (p > 0.05) between treatments. A main effect of calf age (p < 0.05) was observed for concentrations of insulin-like growth factor 1, which was decreased at week 4 compared to week 0. An age by treatment interaction (p < 0.05) was observed for cortisol, which was decreased at week 2 in calves from MEL-treated dams compared to calves from CON-treated dams. Early post-natal growth was altered in offspring born to dams supplemented with dietary melatonin. This could lead to further foetal programming implications in conjunction with post-natal development.

Dietary melatonin alters uterine artery hemodynamics in pregnant Holstein heifers.

The objective was to examine uterine artery hemodynamics and maternal serum profiles in pregnant heifers supplemented with dietary melatonin (MEL) or no supplementation (CON). In addition, melatonin receptor-mediated responses in steroid metabolism were examined using a bovine endometrial epithelial culture system. Twenty singleton pregnant Holstein heifers were supplemented with 20 mg of melatonin (n = 10) or no melatonin supplementation (control; n = 10) from days 190 to 262 of gestation. Maternal measurements were recorded on days 180 (baseline), 210, 240, and 262 of gestation. Total uterine blood flow was increased by 25% in the MEL-treated heifers compared with the CON. Concentrations of progesterone were decreased in MEL vs CON heifers. Total serum antioxidant capacity was increased by 43% in MEL-treated heifers when compared with CON. Activity of cytochrome P450 1A, 2C, and superoxide dismutase was increased in bovine endometrial epithelial cells treated with melatonin, whereas the melatonin receptor antagonist, luzindole, negated the increase in cytochrome P450 2C activity. Moreover, estradiol or progesterone treatment altered bovine uterine melatonin receptor expression, which could potentiate the melatonin-mediated responses during late gestation. The observed increase in total uterine blood flow during melatonin supplementation could be related to its antioxidant properties. Compromised pregnancies are typically accompanied by increased oxidative stress; therefore, melatonin could serve as a therapeutic supplementation strategy. This could lead to further fetal programming implications in conjunction with offspring growth and development postnatally.

Effect of anabolic implants on adrenal cortisol synthesis in feedlot beef cattle implanted early or late in the finishing phase.

Implantation of anabolic steroids to increase growth rate in beef cattle impacts adrenal glucocorticoid production. The mechanism by which combination androgen and estrogen implants reduce cortisol biosynthesis in heifers is not clear. The objective of this study was to identify whether pituitary or adrenal gene expression and liver enzyme activity may contribute to altered serum cortisol concentrations in heifers receiving a combination implant. On d 0 of a 122-d finishing phase, 187 predominantly Angus heifers (361 kg) approximately 14 months old were randomly assigned to one of three implant groups: (1) non-implanted control, (2) implanted at the beginning of the finishing phase (d 0; early implant) with a combination implant (200mg TBA+20mg E2; Revalor 200®), and (3) implanted during the late stage of the finishing phase (d 56; late implant) with Revalor 200®. At d 56, body weight (BW) was greater (P<0.0001) for the early implanted heifers (456 ± 1.9 kg) compared to 437 and 435 (± 1.8) kg for control and late implanted heifers, respectively. Final BW (d 122) was similar between both implanted groups and heavier than non-implanted controls (P<0.0001). Serum cortisol was similar among groups at d 0 (P=0.86) however, by d 28 heifers receiving the combination implant had reduced (P<0.05) serum cortisol concentrations (31.2 ng/mL) compared to controls (49.4 ng/mL) and late (48.2 ng/mL) groups. On d 84 cortisol was similar (P=0.75) among implanted heifers and was less (P<0.01) than non-implanted heifers. Expression of pituitary and adrenal genes involved in glucocorticoid synthesis was evaluated at d 28/29 or 84/85; however, despite decreased serum cortisol in implanted heifers, no change in mRNA expression was demonstrated. Liver CYP3A enzyme activity at d 28/29 was decreased 59% in early implanted heifers compared to control heifers (P=0.01). Additionally, at d 84/85 AKR1C activity was greatest (P=0.01) in control heifers compared to both implanted groups. Data suggest that components of hypothalamic-pituitary-adrenal axis are influenced by exposure to exogenous hormones and this should be recognized when considering cortisol levels as a marker for stress response.

Effect of 2 corpora lutea on blood perfusion, peripheral progesterone, and hepatic steroid-inactivating enzymes in dairy cattle.

The luteal structure that develops postovulation is critical to the facilitation and maintenance of pregnancy in dairy cattle. The objectives of this experiment were to determine if the induction of an accessory corpus luteum (CL), via human chorionic gonadotropin, altered blood perfusion of CL, peripheral concentrations of progesterone, or hepatic steroid-inactivating enzymes. Twenty-eight late-lactation Holstein cows were synchronized using the Ovsynch protocol and randomly assigned to 1 of 2 treatment groups. Cows received either an injection of human chorionic gonadotropin (1,000IU, i.m.) to induce an accessory CL (cows had exactly 2CL in 1 ovary) or no treatment (cows had exactly 1CL). Corpora lutea were examined daily from d 10 to 18 (d 0 was induced ovulation) via Doppler ultrasonography and a blood sample was collected. Volume of the CL was recorded, as well as images and videos of each CL, which were analyzed for blood perfusion. On d 13, a liver biopsy was performed to analyze hepatic steroid-inactivating enzymes. Cows with 1 or 2CL had similar peripheral concentrations of progesterone. Cows with 2CL had similar luteal volumes to cows with 1CL but cows with 2CL had greater total luteal blood perfusion. Hepatic enzyme [cytochrome P450 (CYP) 1A, 3A, and 2C, aldo-keto reductase 1C, and uridine diphosphate glucuronosyltransferase] activities did not differ between cows with 1 and 2CL. Overall, the observed increase in total luteal blood perfusion in cows with 2CL did not correspond to differences in peripheral concentrations of progesterone or clearance of progesterone measured by the hepatic enzyme activity. This could indicate that induction of an accessory CL would not affect concentrations of progesterone necessary to maintain pregnancy.

Hepatic steroid metabolizing enzyme activity during early, mid, and late bovine pregnancy.

The objective was to examine hepatic steroid inactivating enzymes throughout gestation and determine the effect of early to mid-gestation maternal nutrient restriction followed by realimentation on the activity of these enzymes. On day 30 of gestation, cows were assigned to dietary treatments: control (CON; 100% National Research Council; n = 18) and restricted (RES; 60% National Research Council; n = 30). On day 85, cows were slaughtered (CON, n = 6 and RES, n = 6), remained on control (CC, n = 12) and restricted (RR, n = 12), or were realimented to control (RC, n = 11). On day 140, cows were slaughtered (CC, n = 6; RR, n = 6; RC, n = 5), remained on control (CCC, n = 6; RCC, n = 5), or were realimented to control (RRC, n = 6). On day 254, all remaining cows were slaughtered. Jugular blood samples were collected before the slaughter for steroid analysis. At slaughter, maternal liver samples were collected for hepatic enzyme activity analysis. Activity of cytochrome P450 3A decreased (P = 0.05) from mid- to late-gestation. Peroxisome proliferator-activated receptor alpha DNA binding activity was increased (P < 0.01) on day 140 and 254 of gestation vs day 85. Concentrations of estradiol-17ß (E2) increased (P < 0.01) as gestation proceeded, whereas progesterone concentrations (P4) tended to increase (P = 0.06) from mid- to late-gestation. Activity of cytochrome P450 1A and 2C were decreased (P < 0.05) in nutrient restricted cows vs control, whereas concentrations of E2 were increased (P < 0.05) in nutrient restricted cows vs control. A longer period of nutrient realimentation from mid- to late-gestation increased (P < 0.05) aldo-keto reductase 1C activity and decreased (P < 0.05) P4 concentrations compared with the shorter period of nutrient realimentation. In addition, significant negative correlations were observed for cytochrome P450 3A activity vs E2 (r(2) = -0.30; P < 0.05) and aldo-keto reductase 1C activity vs P4 (r(2) = -0.29; P < 0.05). The present study implicates hepatic steroid inactivation in the partial modulation of peripheral concentrations of E2 and P4 during gestation.

A new treatment option for acne scars: allograft dermis.

Unsightly facial scars resulting from acne can be the source of painful emotional trauma. A new option for treating acne scars is described. It is pre-packaged dermal graft material that is easy to use, safe, and effective. A review of current treatment options and the steps for using this material are presented.