Actions of prostaglandin F2alpha and prolactin on intercellular adhesion molecule-1 expression and monocyte/macrophage accumulation in the rat corpus luteum

Expression of intercellular adhesion molecule-1 (ICAM-1) and the accumulation of monocytes/macrophages are inflammatory events that occur during PRL (PRL)-induced regression of the rat corpus luteum. Here we have compared the ability of prostaglandin F2alpha (PGF) and PRL to induce, in rat corpora lutea, inflammatory events thought to perpetuate luteal regression. Immature rats were ovulated with eCG-hCG and then hypophysectomized (Day 0), which resulted in a single cohort of persistent, functional corpora lutea. On Days 9-11, the rats received twice daily injections of saline, PGF (Lutalyse, 250 microg/injection), or PRL (312 microg/injection) to induce luteal regression. Surprisingly, luteal weight and plasma progestin concentrations (progesterone and 20alpha-dihydroprogesterone) did not differ between PGF-treated rats and controls; whereas both luteal weight and plasma progestins declined significantly in PRL-treated rats. Furthermore, corpora lutea of PGF-treated rats and controls contained relatively minimal ICAM-1 staining and few monocytes/macrophages. In contrast, but as expected, corpora lutea of PRL-treated rats stained intensely for ICAM-1 and contained numerous monocytes/macrophages. In an additional experiment, there was no indication that luteal prostaglandin F2alpha receptor mRNA diminished as a result of hypophysectomy. These findings suggest that prolactin, not PGF, induces the inflammatory events that accompany regression of the rat corpus luteum.     

Repeated exposure to prolactin is required to induce luteal regression in the hypophysectomized rat

We investigated whether prolactin (PRL) treatments resembling the intermittent PRL surges of estrous cycles could induce luteal regression in hypophysectomized rats. Immature female rats were stimulated to ovulate and form corpora lutea with exogenous gonadotropins, and were hypophysectomized following ovulation. A single s.c. injection of either vehicle (VEH) or PRL was administered to each rat on post-hypophysectomy Day 8 and again on Day 11. The four resulting treatment groups consisted of rats that received two injections of VEH, VEH followed by PRL, PRL followed by VEH, or two injections of PRL. Rats were killed 24 or 72 h following the second injection. Plasma 20alpha-dihydroprogesterone, luteal weight, and total luteal protein were determined. One ovary was sectioned for immunohistochemistry for monocytes/macrophages, apoptotic nuclei, and major histocompatibility class II (MHC II) molecules. No effect of time (following injection) was observed on any endpoint, indicating that PRL does not have an ongoing regressive action. Time groups from within each treatment group were therefore pooled for analysis. Significant declines (P: < 0.05) in plasma concentrations of 20alpha-dihydroprogesterone, luteal weight, and protein per corpus luteum occurred only after two injections of PRL. Numbers of luteal monocytes/macrophages, apoptotic nuclei, and MHC II-positive cells were low in all groups; numbers of luteal monocytes/macrophages increased following two injections of PRL (P: < 0.05). We conclude that PRL has a cumulative regressive effect on the corpus luteum of the hypophysectomized rat. Drawing a parallel with the estrous cycle, we suggest that continued exposure to PRL, over several cycles, is necessary to induce full luteal regression.     

Prolactin-induced expression of intercellular adhesion molecule-1 and the accumulation of monocytes/macrophages during regression of the rat corpus luteum

Intercellular adhesion molecule-1 (ICAM-1) is thought to facilitate the recruitment and migration of monocytes/macrophages to sites of inflammation. Here we investigated whether the luteolytic effect of prolactin in the hypophysectomized rat is associated with the expression of ICAM-1. In addition, we examined the effect of exogenous testosterone (or its potential conversion to estradiol endogenously) on the corpus luteum to address recent speculation that ovarian steroids might augment luteal regression. Immature, 30-day-old rats were ovulated with eCG and hCG and then hypophysectomized; this resulted in a single cohort of persistent corpora lutea. The rats were assigned randomly into four treatment groups: vehicle treatment without or with testosterone (VEH-T4, VEH+T4) and prolactin treatment without or with testosterone (PRL-T4, PRL+T4). Corpora lutea of control rats exhibited minimal ICAM-1 staining and contained relatively few monocytes/macrophages. In contrast, corpora lutea of prolactin-treated rats exhibited prominent ICAM-1 staining and contained numerous monocytes/macrophages. Testosterone did not overtly affect ICAM-1 staining, numbers of monocytes/macrophages, or concentrations of plasma progestins (progesterone and 20alpha-dihydroprogesterone) in either VEH or prolactin treatment groups; notwithstanding, luteal weights increased significantly in response to testosterone in VEH+T4 rats compared to VEH-T4 rats and prolactin-treated rats. We conclude that ICAM-1 expression and monocyte/macrophage accumulation are associated with prolactin-induced luteal regression in the rat and that these aspects are not influenced by testosterone.     

Total monoamine oxidase activity in the hypothalamus, ovary and uterus of rats with an extreme number of ovarian corpora lutea

The activity of total monoamine oxidase (MAO) in the rat ovary and uterus fluctuates significantly under various physiological conditions. We analyzed total MAO activity in the hypothalamus, uterus and ovary in adult rats, having an extreme number of corpora lutea (hyperluteinized ovaries) resulting from the mechanical lesions in the posterior hypothalamic region of neonatal rats. Total MAO activity in the hypothalamus (30.21 +/- 1.53 pmol/mg tissue/min) and uterus (3.16 +/- 0.61 pmol/mg tissue/min) of rats with hyperluteinized ovaries did not show a significant difference as compared to that of intact controls (31.09 +/- 1.72 and 2.90 +/- 0.40 pmol/mg tissue/min, respectively). In contrast, in the ovaries of hyperluteinized rats, total MAO activity (21.16 +/- 1.70 pmol/mg tissue/min) was significantly higher (p<0.01) when compared to that of intact controls (13.61 +/- 1.30 pmol/mg tissue/min). The increased MAO activity in the hyperluteinized ovaries may be attributed to the increased number of transformed and accumulated corpora lutes as a consequence of diminished luteolysis.     

Reactivation of regressing corpora lutea by estradiol in the pregnant rat: dependence on placental lactogen

Previous investigations have clearly demonstrated that estradiol maintains corpus luteum function. However, it is unknown whether estradiol can restimulate progesterone synthesis and/or growth of corpora lutea that have already undergone luteolysis. The present study was designed to determine 1) whether estradiol can reactivate the steroidogenic capacity and/or growth of corpora lutea that are deprived of luteotropic support, 2) whether estradiol affects progesterone metabolism, and 3) whether the action of estradiol is related to levels of rat placental lactogen in the peripheral circulation. Rats were hypophysectomized and hysterectomized on Day 12 of pregnancy and were treated between Days 12 and 15 with either estradiol (100 micrograms/day) or 1-cm testosterone implants. Both treatments are known to maintain luteal concentrations of estradiol at physiological levels. In vivo treatment with either estradiol or testosterone prevented the drop in progesterone production and maintained the concentration of serum progesterone at levels found in intact pregnant rats. This action was not due to an alteration in the rate of metabolism of progesterone to 20 alpha-hydroxyprogesterone, since peripheral serum levels and in vitro production of 20 alpha-hydroxyprogesterone were unaffected by estradiol. When testosterone treatment was started 24 and 48 h after hypophysectomy and hysterectomy, at a time when progesterone production had been markedly reduced and luteal growth had ceased, a restimulation of both progesterone synthesis and luteal growth was observed. However, in all cases the ability of estradiol to stimulate progesterone was finite, and corpora lutea ceased to respond by Day 17, coincident with the time that rat placental lactogen became undetectable in the circulation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of RU 486 on luteal function in the early pregnant rat

A dose of 30 mg RU 486/kg, an antiprogesterone, was administered to pregnant rats on Day 2 (Group 1) or Day 4 (Group 2) of pregnancy. RU 486 significantly changed serum progesterone and oestradiol concentrations and luteal 3 beta-HSD and 20 alpha-HSD activities in Group 1, and implantation was significantly inhibited. The luteal 3 beta-HSD activity in Group 2 rats on Day 6 was significantly (P less than 0.01) lower than the control value (7.5 +/- 0.6 and 10.1 +/- 0.6 mU/mg protein respectively). This decline in the 3 beta-HSD activity was followed by a marked decrease in the serum progesterone concentration, resulting in a significant decrease of the progesterone/oestradiol ratio and implantation was completely inhibited. The 20 alpha-HSD activity, which could not be detected on Day 6 in the control rats, was twice as great in Group 2 than in Group 1 rats (17.5 +/- 1.2 and 7.4 +/- 3.1 mU/mg protein respectively). Ultrastructural examination of corpora lutea of Group 2 rats confirmed luteolysis. These results suggest that RU 486 has a luteolytic effect and its anti-implantation effect is concomitant with luteolysis of the corpora lutea of pregnancy.     

Receptors for prostaglandins F2 alpha and E2 in ovine corpora lutea during maternal recognition of pregnancy.

Plasma membrane receptors for prostaglandins (PG) F2 alpha and E2 were quantified in ovine corpora lutea obtained from nonpregnant and pregnant ewes on Days 10, 13, and 15 post-estrus, and from additional ewes on Days 25 and 40 of pregnancy. Regardless of reproductive status or day post-estrus, concentrations of luteal receptors for PGF2 alpha were 7- to 10-fold greater than those for PGE2. In pregnant ewes the concentration of receptors for PGF2 alpha was highest on Day 10 (35.4 +/- 2.8 fmol/mg) and lowest on Day 25 (22.3 +/- 2.5 fmol/mg). A difference in the concentration of luteal receptors for PGF2 alpha between pregnant and nonpregnant ewes was apparent only on Day 15 post-estrus, at which time the concentration of receptors for PGF2 alpha was higher in pregnant ewes than in nonpregnant ewes (27.1 +/- 2.7 vs. 17.7 +/- 2.7 fmol/mg). Concentrations of receptors for PGE2 in pregnant ewes were similar (p > 0.05; 2.8 +/- 0.3 to 3.7 +/- 0.2 fmol/mg) between Days 13 and 40 but were higher (p < 0.05) than in corpora lutea obtained from nonpregnant ewes on Days 10 (5.0 +/- 0.4 vs. 4.1 +/- 0.2 fmol/mg) and 15 (3.7 +/- 0.2 vs. 2.0 +/- 0.4 fmol/mg) post-estrus. Although concentrations of receptors for both PGF2 alpha and PGE2 were lowest in corpora lutea obtained from nonpregnant ewes on Day 15, this was not due to luteal regression since the weights and concentrations of progesterone in corpora lutea on Day 15 were not lower than those for corpora lutea obtained on Days 10 and 13.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of hysterectomy and uterine decidualization on in vivo levels of prostaglandins in the corpus luteum of adult pseudopregnant rats

A possible role of the uterus in regulating content of luteal prostaglandins (PGs) was investigated. Pseudopregnancy was induced in adult virgin female rats by mating them with vasectomized male rats. On Day 5 of pseudopregnancy, decidualization of the uterus was induced or hysterectomy was performed. As controls, intact pseudopregnant animals with a luteal phase of 13 +/- 1 days were used. Measurements of in vivo tissue levels of PGF2 alpha, PGE2, and 6-keto-PGF1 alpha were performed by RIA after homogenization and extraction procedures in CL of pseudopregnancy and remainder of ovaries on Days 5, 13, and 19. Serum levels of progesterone and 20 alpha-dihydroprogesterone were determined by RIA. In hysterectomized animals, PGF2 alpha levels increased 2.5-fold in corpora lutea on Day 13 compared with levels on Day 5 of pseudopregnancy, but were still lower than in control rats undergoing functional luteolysis on Day 13. Decidual-tissue-bearing rats exhibited low levels of PGF2 alpha on Day 13 of pseudopregnancy. On Day 19, when luteolysis had occurred in decidual-tissue-bearing and hysterectomized rats, as judged by plasma levels of progestins, luteal content of PGF2 alpha was elevated to a similar level as that in control animals undergoing functional luteolysis on Day 13. When data pooled from control, decidual-tissue-bearing and hysterectomized rats were analyzed, a highly significant inverse correlation (r = -0.72, n = 46, p less than 0.001) between luteal PGF2 alpha content and ratio of plasma progestins was found.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of a 3beta-hydroxysteroid dehydrogenase inhibitor on monocyte-macrophage infiltration into rat corpus luteum and on apoptosis: relationship to the luteolytic action of prolactin

The administration of prolactin to hypophysectomized rats results in regression of the corpora lutea, accompanied by immune-inflammatory events such as infiltration of monocytes and macrophages. Recent reports indicate an autocrine role for progesterone during the lifespan of the corpus luteum. In the present study, an inhibitor of 3beta-hydroxysteroid dehydrogenase, Trilostane, was used to investigate the hypothesis that a decrease in luteal tissue steroids precipitates the cascade of immune-inflammatory events leading to luteal regression in prolactin-treated hypophysectomized rats. Immature rats were induced to ovulate by administering eCG-hCG, and hypophysectomized on the day after ovulation (at 32 days of age). Rats were injected s.c. 9-11 days after hypophysectomy with (a) Trilostane (80 mg kg(-1) day(-1)), (b) ovine prolactin (500 mg day(-1)), (c) Trilostane plus prolactin, or (d) vehicle. Plasma and luteal tissue progesterone and 20alpha-dihydroprogesterone ('progestin') were quantified; luteal tissue monocytes-macrophages and apoptotic nuclei were counted, and luteal wet mass was determined. Rats treated with prolactin alone showed the expected markers of luteal regression: decreased plasma progestin, increased numbers of monocytes-macrophages and apoptotic nuclei in luteal tissue, and decreased luteal wet mass; however, progestin concentration in luteal tissue was unchanged. Treatment with Trilostane reduced plasma and luteal tissue progestin, but did not result in an infiltration of monocytes-macrophages or increased numbers of apoptotic nuclei in the corpora lutea, or any change in luteal wet mass. Trilostane in combination with prolactin reduced plasma and luteal tissue progestin and produced the expected markers of regression, with the exception of luteal tissue mass, which remained unchanged. In conclusion, inhibition of steroidogenesis does not initiate luteal regression or augment prolactin-induced luteal regression in hypophysectomized rats. Prolactin-induced infiltration of monocytes-macrophages is not accompanied by a decrease in luteal tissue progestin, at least in the early stages of luteal regression.     

The effect of a depot injection of recombinant bovine somatotropin on follicular development and embryo yield in superovulated Holstein heifers

Superovulated Holstein heifers (n = 32) were given a depot injection of 500 mg recombinant bovine somatotropin (rBST) or vehicle at Day 4 of the estrous cycle (7 days before the first FSH injection); at Day 11, coincidentally with the first FSH injection; or at Day 15, the time of artificial insemination. Embryos were collected nonsurgically, and the number of corpora lutea was counted by ultrasonography at Day 7 after insemination. Blood samples were taken every second day, from Day 2 of the superovulatory cycle until the day of embryo collection, and were analyzed for progesterone, somatotropin and insulin-like growth factor-1 (IGF-1). Somatotropin-treated heifers at Day 11 had a significantly higher mean number of corpora lutea than the controls (18.1 vs 13.4; P 0.63), but it was negatively correlated with progesterone (P 相似文献   

Changes in rat luteal ultrastructure and P450scc mRNA and protein content after in vivo treatment with a gonadotropin-releasing hormone agonist

Previous studies have demonstrated that plasma progesterone levels decrease in pregnant rats treated in vivo with a gonadotropin-releasing hormone agonist (GnRH-Ag), without changes in testosterone or estradiol levels in ovarian vein plasma. The objective of this study was to determine the loci of GnRH-Ag disruption of progesterone synthesis by examining luteal mitochondria, lipid droplets, cellular composition, and P450 side-chain cleavage (P450scc) enzyme and mRNA content in the pregnant rat. On Day 7 or 11 of pregnancy, osmotic minipumps containing GnRH-Ag were implanted into 5-7 rats. Sham operations were performed on 5-6 controls at each time period. Five micrograms per day of GnRH-Ag were released for about 24 h, after which corpora lutea and jugular vein plasma were collected. The corpora lutea were prepared for microscopy or analyzed for P450scc enzyme and mRNA content. Plasma progesterone levels were measured by RIA. In those rats treated with GnRH-Ag, progesterone levels had decreased, and within the luteal cells, there was an increase in the number of lipid droplets and a decrease in the number of tubular cristae within the mitochondria. Concomitantly, P450scc enzyme and mRNA content decreased on both Day 8 and Day 12 of pregnancy. Also, GnRH-Ag treatment decreased the ratio of large to small steroidogenic luteal cells on Day 8 of pregnancy, but did not alter cellular ratios on Day 12 of pregnancy. These observations suggest that treatment with GnRH-Ag inhibits progesterone synthesis by decreasing the amount of P450scc mRNA and enzyme content, which may alter the mitochondrial cristae structure on Day 8 and Day 12 of pregnancy. The reduction in tubular cristae and P450scc enzyme in the mitochondria may account for the increase in lipid droplets, as less cholesterol is converted to pregnenolone. An additional mechanism of inhibition may be the reduction in the number of large steroidogenic luteal cells, which appear to be the major source of progesterone in the rat corpus luteum on Day 8 of pregnancy.     

Measurement of inhibin A and follicular status predict the response of ewes to superovulatory FSH treatments

Variability in superovulatory response to FSH stimulation is common to most mammals and imposes practical problems for assisted reproduction. In sheep, we have studied if this response is related to the ovarian follicular population and activity before the stimulation. During the breeding season, 30 ewes were treated with 40 mg FGA sponges for 14 days and 125 microg cloprostenol injection on Day 12, considering Day 0 as the day of progestagen insertion. Superovulatory response was induced with two different FSH regimes using the same total dose (8.8 mg), administered twice daily from 60 h before to 24 h after progestagen withdrawal. At the first FSH injection, all follicles > or = 2 mm were observed by transrectal ultrasonography and plasma FSH and inhibin A levels were determined. The number of corpora lutea and the number of and viability of recovered embryos in response to the treatment were determined on Day 7 after sponge withdrawal. No significant differences were found between treatments. The total mean number of corpora lutea (11.5 +/- 1.2) and recovered embryos (7.9 +/- 1.1) were positively correlated (P < 0.05 and <0.01, respectively) with the number of small antral follicles (2-3 mm: 9.2 +/- 0.7) and inhibin A concentration (240 +/- 18 pg/ml; P < 0.05 for corpora lutea and P < 0.005 for recovered embryos) observed at the onset of the superovulatory treatment, which was also positively correlated with the number of viable embryos (5.8 +/- 0.9, P < 0.005). In 18 ewes with follicles > or = 6 mm prior to FSH treatment, the ovulation rate was unaffected but the number of embryos (6.1 +/- 0.9 versus 11.6 +/- 2; P < 0.05) and their viability (4.5 +/- 0.8 versus 8.5 +/- 2; P < 0.05) was reduced. The lower number of embryos produced when a large follicle is present suggest that a proportion of the smaller follicles are in early stages of atresia and the developmental competence of their oocyte is compromised.     

OBSERVATIONS ON THE FINE STRUCTURE OF LUTEIN CELLS : II. The Effects of Hypophysectomy and Mammotrophic Hormone in the Rat

Corpus luteum formation was induced in 26-day-old rats which were subsequently hypophysectomized and injected with mammotrophic hormone (MH, LTH). Sections of corpora lutea from these animals were examined with the electron microscope and compared with similarly prepared (Caulfield's fixed, Araldite embedded) corpora from normal pregnancy and from controls, the latter consisting of corpora prior to hypophysectomy and corpora from uninjected rats 7 to 14 days after hypophysectomy. Lutein cells from corpora lutea of injected animals and of normal pregnancy are characterized by abundant, tortuous, tubular agranular endoplasmic reticulum and by mitochondria, many of which are disc-shaped with dense matrices and both villiform and lamelliform cristae. The endoplasmic reticulum is most abundant in lutein cells from pregnant animals, in which cells it is in the form of thin, highly tortuous tubules. The form of the lipid droplets seen in cells of stimulated animals varies greatly. Marginal foldings of the lutein cells on the perivascular space were found in all instances. Lutein cells from hypophysectomized animals have a less highly developed agranular endoplasmic reticulum. The mitochondria have irregular outlines and a relatively lucid matrix. The lipid droplets in these cells show less tendency to be extracted, but are not so large or abundant as in the cells of onset controls. Granules believed to contain lipid pigments are common in the lutein cells of these control animals. It is suggested that lutein cells from corpora lutea which are actively secreting progesterone may be readily distinguished from lutein cells from non-active corpora by means of the multiple characteristics enumerated. It is further suggested that mammotrophic hormone has a general effect on the metabolism of lutein cells rather than solely affecting a specific organelle, the abundance or composition of which may be the limiting factor in the production of progesterone.     

Prostaglandin metabolism in the ovine corpus luteum: catabolism of prostaglandin F(2alpha) (PGF(2alpha)) coincides with resistance of the corpus luteum to PGF(2alpha)

To examine possible mechanisms involved in resistance of the ovine corpus luteum to the luteolytic activity of prostaglandin (PG)F(2alpha), the enzymatic activity of 15-hydroxyprostaglandin dehydrogenase (PGDH) and the quantity of mRNA encoding PGDH and cyclooxygenase (COX-2) were determined in ovine corpora lutea on Days 4 and 13 of the estrous cycle and Day 13 of pregnancy. The corpus luteum is resistant to the action of PGF(2alpha) on Days 4 of the estrous cycle and 13 of pregnancy while on Day 13 of the estrous cycle the corpus luteum is sensitive to the actions PGF(2alpha). Enzymatic activity of PGDH, measured by rate of conversion of PGF(2alpha) to PGFM, was greater in corpora lutea on Day 4 of the estrous cycle (P < 0.05) and Day 13 of pregnancy (P < 0.05) than on Day 13 of the estrous cycle. Levels of mRNA encoding PGDH were also greater in corpora lutea on Day 4 of the estrous cycle (P < 0. 01) and Day 13 of pregnancy (P < 0.01) than on Day 13 of the estrous cycle. Thus, during the early estrous cycle and early pregnancy, the corpus luteum has a greater capacity to catabolize PGF, which may play a role in the resistance of the corpus luteum to the actions of this hormone. Levels of mRNA encoding COX-2 were undetectable in corpora lutea collected on Day 13 of the estrous cycle but were 11 +/- 4 and 44 +/- 28 amol/microgram poly(A)(+) RNA in corpora lutea collected on Day 4 of the estrous cycle and Day 13 of pregnancy, respectively. These data suggest that there is a greater capacity to synthesize PGF(2alpha), early in the estrous cycle and early in pregnancy than on Day 13 of the estrous cycle. In conclusion, enzymatic activity of PGDH may play an important role in the mechanism involved in luteal resistance to the luteolytic effects of PGF(2alpha).     

Hormonal regulation of estradiol biosynthesis, aromatase activity, and aromatase mRNA in rat ovarian follicles and corpora lutea

To determine the molecular basis for changes in aromatase (P450arom) activity in rat ovarian follicles and corpora lutea, seven clones for rat P450arom cDNA have been identified and isolated from a rat granulosa cell λgtll cDNA expression library using a 62 mer deoxyoligonucleotide probe (derived from an amino acid sequence of purified human placental aromatase) and a human placental P450arom cDNA probe. One of the rat P450arom cDNA clones contained an insert 1.2 kb in size. Both the human 1.8 kb cDNA and the rat 1.2 kb cDNA probes hybridized to a single species of P450arom mRNA that was 2.6 kb in size. Northern blot analysis revealed that corpora lutea isolated on day 15 of pregnancy contained high amounts of P450arom mRNA, whereas granulosa cells of antral follicles of hormonally primed, hypophysectomized rats (i.e., those from which mRNA was isolated to construct the cDNA library) contained only low amounts of P450arom mRNA. The lower amounts of P450arom in granulosa cells of preovulatory follicles in the estradiol-follicle-stimulating hormone primed hypophysectomized rats were unexpected because follicles incubated in medium containing testosterone substrate produce more estradiol than do corpora lutea isolated on day 15 of pregnancy and incubated under similar conditions. Additional studies will determine the hormonal events responsible for the elevated amounts and constitutive maintenance of P450arom mRNA and aromatase activity in luteal cells in vivo and in vitro.     

Relationships between ovarian blood flow and ovarian response to eCG-treatment of dairy cows

The goal of the present study was to investigate ovarian blood flow and ovarian response in cows undergoing a gonadotropin treatment to induce a superovulatory response, using transrectal colour Doppler sonography. Forty-two cows including 19 cross-bred, 14 German Holstein and 9 German Black Pied cows were examined sonographically before hormonal stimulation on Day 10 of the oestrous cycle, three days after administration of eCG (Day 13) and seven days after artificial insemination (Day 7(p.i.)). After each Doppler examination, blood was collected for determination of total oestrogens (E) and progesterone (P4) in peripheral plasma. The blood flow volume (BFV) and pulsatility index (PI), which is a measure for blood flow resistance, were determined in the ovarian artery, and B-mode sonography was used to count dominant follicles and corpora lutea. Important criteria to assess the ovarian response following the hormonal treatment were the number of follicles >5mm in diameter on Day 13 and the number of corpora lutea on Day 7(p.i.) per cow. The number of follicles ranged from 2 to 61 (mean+/-S.E.M.: 17.5+/-1.7) and corpora lutea from 0 to 50 (mean+/-S.E.M.: 17.0+/-1.6). The BFV increased from 28.4 to 45.0 ml/min between Days 10 and 13 and reached a maximum of 108.5 ml/min on Day 7(p.i.) The PI decreased from 6.25 on Day 10 to 4.70 on Day 13 and to 2.10 on Day 7(p.i.) The BFV and PI on Day 13 did not correlate with the number of follicles (P>0.05). However, on Day 7(p.i.) the number of corpora lutea correlated positively with the BFV (r=0.64; P<0.0001), and an inverse relationship was found for the PI (r=-0.51; P=0.0005). There were no correlations (P>0.05) between the BFV and PI on Day 10 and the number of follicles on Day 13 or the number of corpora lutea on Day 7(p.i.) Results of the present study show that in cows, a hormonal treatment to induce a superovulatory response yielded a marked increase in BFV and a marked decrease in PI in the ovarian artery. However, there was no correlation between BFV and PI in the ovarian arteries before hormonal stimulation and the number of follicles and corpora lutea that developed after stimulation. Thus BFV and PI measured in the ovarian arteries have limited diagnostic value to predict the outcome of a gonadotropin treatment.     

Lipoprotein lipase activity in the bovine corpus luteum during the estrous cycle and early pregnancy.

Lipolytic activity measured at pH 8.6 in bovine corpora lutea exhibited classical properties of lipoprotein lipase (LPL) in terms of serum and heparin stimulation and NaCl inhibition. LPL activity was measured in 23 corpora lutea collected at different stages of the estrous cycle and early pregnancy. The LPL activity in cyclic corpora lutea (mumole FA released/hr/100 mg acetone powder) was low at Days 4-8 of the estrous cycle (3.1 +/- 1.5: mean +/- SE) and at Days 19-20 (1.6 +/- 0.6). However, high activity of the enzyme was found at Days 12-15 of the cycle (11.8 +/- 1.8); these concentrations were significantly (P less than 0.01) elevated over those found at Days 4-8 and 19-20. The enzyme activity began to decline at Days 16-18 of the estrous cycle (5.1 +/- 1.7). Low enzyme activity was found in the corpora lutea removed from two cows at Day 22 of pregnancy. Progesterone concentrations were measured in 16 of the 23 corpora lutea and a good correlation (r = 0.75, P less than 0.01) was found between lipoprotein lipase and progesterone concentrations of the tissue. The data suggest that LPL may be involved in controlling the transfer of fatty acids, including arachidonic, from plasma lipoproteins to luteal tissue.     

In vivo levels of prostaglandin F2 alpha, E2 and prostacyclin in the corpus luteum of pregnant and pseudopregnant rats

Prostaglandin F2 alpha (PGF2 alpha) is a well-known luteolytic factor in the rat corpus luteum. To investigate a possible luteal origin of PGF2 alpha, measurements of this prostaglandin were performed in different luteal tissues in vivo. Prostaglandin E2 (PGE2) and the stable metabolite of prostacyclin, 6-keto-PGF1 alpha, were assayed simultaneously. Corpora lutea of different ages from 57 pregnant and pseudopregnant rats (mated with sterile males) were rapidly excised, dissected in 0 degree C indomethacin solution, homogenized, and extracted for prostaglandins with solid-phase extraction cartridges. Prostaglandins were determined by radioimmunoassay. Plasma levels of progesterone and 20 alpha-dihydroprogesterone were also monitored. In the adult pseudopregnant rat model, luteolysis occurs at Day 13 +/- 1, and maximal levels of all three prostaglandins were detected on Day 13 of pseudopregnancy: 0.40 +/- 0.02, 2.6 +/- 0.29, and 1.76 +/- 0.24 pmol/mg protein (mean +/- SEM, n=7) for PGF2 alpha, PGE2, and 6-keto-PGF1 alpha respectively. In pregnant rats, on the corresponding day, levels were considerably lower: 0.15 +/- 0.02, 0.90 +/- 0.13, and 0.50 +/- 0.06 pmol/mg protein (mean +/- SEM, n=9, p less than 0.0001), respectively. Luteal levels in pregnant rats showed a continuous decline on Days 13 and 19 for all prostaglandins measured, whereas in pseudopregnant rats an increment of PGF2 alpha was noted between Days 7 and 13 and remained high on Day 19. PGE2 closely followed levels of PGF2 alpha, but at a 5- to 10-fold higher level. The coefficient of correlation between PGF2 alpha and PGE2 in the luteal compartment of both models was 0.87 (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Reappearance of cyclicity of vaginal smears in androgen-sterilized rats following thyroidectomy

During studies on the mechanism of hypersensitivity to gonadotropins of thyroidectomized rat ovary, results were obtained which suggest an increase in the endogenous luteinizing hormone (LH) release after thyroidectomy in androgen-sterilized rats. Female rats were injected subcutaneously with 1 mg of testosterone propionate dissolved in .05 ml of olive oil on Day 5 after birth. At the age of 10-12 weeks, those animals which showed persistent vaginal cornification were thyroidectomized. Within 1-2 days after thyroidectomy, the thyroidectomized rats exhibited leukocytic and epithelial vaginal smears for 2-6 days. Irregular cyclicity with the pattern of 2-6 days diestrus and 3-10 days estrus persisted for 1 month. Histological examination revealed that the corpora lutea were intermingled with a number of cystic follicles in the ovaries of the androgen-sterilized and throidectomized rats while the ovaries of androgen-sterilized controls had vesicular follicles but were devoid of corpora lutea. The results indicate a rapid enhancement in the LH release in androgen-sterilized rats following thyroidectomy.