Increase in plasma testosterone concentrations after injection of adrenocorticotrophin into the boar.

Injection of a 'rapid-acting' preparation of porcine adrenocorticotrophic hormone (ACTH) into three boars resulted in a rapid rise in plasma testosterone levels which accompanied the expected rise in plasma corticosteroids. Urinary dehydroepiandrosterone (DHA) levels were measured in one boar and were found to be raised also. The results suggest that the effect involved enhaced testicular steroid activity and was related to the dosage of ACTH employed. This action of ACTH is thought to be mediated through the adrenal cortex since injection of cortisol elecited a rise in testosterone similar to that observed after injection of ACTH. ACTH had no effect on testosterone levels in a castrated boar. When a 'long-acting' preparation of ACTH was administered to two boars twice daily for 5 days, testosterone levels were depressed. It was concluded that ACTH may bring about an increase or a decrease in plasma testosterone levels in the boar depending upon the length of time increased levels of ACTH are present in the circulation.

Effect of cortisol on the response to gonadotrophin releasing hormone in the boar.

The effect of intracarotid perfusion of 40 mg cortisol for 1 h on the hormonal response to three different doses of an intramuscular injection of synthetic gonadotrophin releasing hormone (GnRH) was compared to that of GnRH injected during intracarotid perfusion with 0.9% (w/v) NaCl solution in five boars. The increase in production of LH, above basal values, in response to injection of 0.25 microgram GnRH midway through perfusion was only slightly greater (P greater than 0.05) in boars receiving cortisol compared to that when the same boars received saline. When 0.5 microgram GnRH was injected midway through perfusion, a significantly greater (P less than 0.05) increase in production of LH above basal levels occurred during cortisol administration than occurred when saline was given. Injection of 1.0 microgram GnRH in boars during cortisol perfusion resulted in significantly greater (P less than 0.01) production of LH, above basal levels, compared to the increase above basal levels that resulted when this dose of GnRH was given during intracarotid saline treatment. Increases in plasma values of testosterone reflected the increases in levels of LH. The results suggest that acute elevations in plasma cortisol may, under some circumstances, enhance the increased production of LH in the boar by increasing the responsiveness of the anterior pituitary gland to GnRH.

ACTH treatment disrupts ovarian IGF-I and steroid hormone production.

Hyper-adrenal activity and increased glucocorticoid hormone release are associated with disruptions in reproductive function and adverse effects on the ovary. The aim of this investigation was to determine whether elevated glucocorticoid hormone levels can influence ovarian IGF-I synthesis and action in vivo. To elevate endogenous glucocorticoid levels, gilts were treated with ACTH during the luteal phase of the oestrous cycle (days 9-13) while the control group received saline. The gilts were subsequently ovariectomized on either day 14 or day 18 of the oestrous cycle. Follicular fluid (FF) was collected from individual follicles; IGF-I and steroid hormone concentrations were determined by radioimmunoassay, and IGF-binding protein (IGFBP) expression was assessed by Western ligand blotting. Granulosa cells were also recovered and placed in culture to determine IGF-I, progesterone (P(4)) and oestradiol-17beta (E(2)) production levels. The cells were cultured in serum-free medium for 5 days and supplemented with: (a) media alone, (b) IGF-I, (c) FSH and androstenedione (A(4)), or (d) IGF-I with FSH and A(4). The FF from ACTH-treated gilts was characterized by elevated (P<0.05) cortisol levels on day 14 and lower (P<0.05) E(2) values on both day 14 and day 18. Lower (P<0.05) IGF-I concentrations were also measured in the FF of ACTH-treated gilts collected on day 18. This altered hormone profile in FF was associated with impaired IGF-I and steroid hormone synthesis by granulosa cells. IGF-stimulated P(4) production (P<0.01) by cells recovered from ACTH-treated gilts on day 14 was lower (P<0.05). By day 18, IGF-I, P(4) and E(2) production by cells from the ACTH group were all significantly (P<0. 05) lower. These results demonstrate that increased glucocorticoid concentrations can disrupt subsequent ovarian IGF-I synthesis and IGF action in vivo and can, potentially, impair follicle maturation.

Fibronectin concentrations correlate with ovarian follicular size and estradiol values in equine follicular fluid.

The amounts of total protein, albumin, fibronectin, alpha 2-macroglobulin (alpha 2-M), immunoglobulin G, ceruloplasmin and antithrombin were determined in fluids collected from 53 preovulatory equine follicles and compared with the contents of estradiol-17 beta, progesterone and androstenedione, with follicle size and the amounts of the equivalent proteins in normal equine plasma. The concentration of fibronectin and the fibronectin/albumin ratios increased significantly with follicle size and with follicular estradiol levels. The alpha 2-M levels and alpha 2-M/albumin ratios correlated with follicle size but not with hormone content. Both fibronectin and alpha 2-M were present in lower amounts in follicular fluid compared with plasma while the other proteins were present in similar amounts. Among the proteins evaluated, there was a positive correlation between the amount of the protein in the follicular fluid and the molecular weight of the protein.

Plasma concentrations of immunoreactive relaxin activity and progesterone in the pregnant Asian elephant (Elephas maximus).

Immunoreactive relaxin activity and progesterone concentrations in weekly plasma samples were measured throughout six pregnancies in five Asian elephants (Elephas maximus). One animal aborted, one delivered a stillborn calf at term and the remaining pregnancies concluded normally with living young. Immunoreactive relaxin activity increased by week 20 of pregnancy to reach a mean peak concentrations of > 6 ng/ml in the second trimester. This was followed by a slow decline beginning approximately at 30 weeks before term. A smaller, secondary relaxin rise was observed during the final eight weeks preceding parturition and circulating concentrations remained above pre-pregnancy baseline values for 72 h after birth. In contrast, progesterone concentrations increased immediately after mating and rose to a maximum of > 2 ng/ml by mid-gestation. As with relaxin, progesterone concentrations began to decline gradually approximately 30 weeks before birth. More frequently collected samples before, during and after parturition revealed a decline to pre-pregnancy levels between 2-5 days before parturition, in contrast to elevated relaxin levels (1 ng/ml) during this time. The aborted pregnancy at week 35 was accompanied by a precipitous decline in both immunoreactive relaxin and progesterone concentrations one week before the visible termination of the pregnancy. The delivery of the term stillborn calf occurred five weeks after both immunoreactive relaxin and progesterone concentrations had declined to pre-pregnancy values. Results suggest that immunoreactive relaxin may be important, along with progesterone, in the maintenance of pregnancy in the Asian elephant as well as playing a role in preparation for birth and possibly to indicate foetal well-being.

Glucocorticoid influence on porcine granulosa cell IGF-I and steroid hormone production in vitro.

The effect of cortisol on granulosa cell (GC) insulin-like growth factor I (IGF-I) synthesis, and IGF-mediated steroid production was examined at various stages of follicle maturation. Granulosa cells were recovered from gilts on Days 14, 18, and 20 of the estrous cycle, while luteinizing GC were recovered on Day 21, just prior to ovulation. The cells were cultured in serum-free medium with increasing concentrations of cortisol (0, 1, 10, and 100 microg/mL) for 5 d with or without IGF-I stimulation (10 ng/mL). During culture all cells were supplemented with FSH and androstenedione (A4). Cellular IGF-I, progesterone (P4) and estradiol-17beta (E2) production was determined by specific radioimmunoassays (RIA), and cell proliferation was assessed. Granulosa cell IGF-I and steroid hormone synthesis increased (P<0.05) with follicle maturation. Direct exposure to high cortisol concentrations, however, altered both IGF-I synthesis and action. Cortisol treatment lowered (P<0.05) IGF-I production by GC recovered on Days 18, 20, and 21. Furthermore, it reduced (P<0.05) IGF-stimulated P4 synthesis at all stages and decreased (P<0.05) IGF-stimulated E2 synthesis by cells recovered on Day 14. In contrast, cortisol enhanced (P<0.05) FSH-stimulated P4 production by GC collected on Days 14 and 18. The opposing effects on FSH and IGF-I action indicate that cortisol did not promote an overall suppressive effect on cell function, nor did it impair cell proliferation. Hence, these results demonstrate that elevated cortisol concentrations can disrupt both IGF-I synthesis and IGF-mediated actions by porcine GC under in vitro conditions, and that specific disruptions are dependent on the stage of follicle maturation.

Effect of dexamethasone on secretion of luteinizing hormone and testosterone in the boar.

Eight adult, Yorkshire-Landrace crossbred boars were used to evaluate the effects of the synthetic glucocorticoid, dexamethasone (DXM) on the secretion of luteinizing hormone (LH) and testosterone. Four treatments of 4 d each were administered: 1) 2 ml i.m. of 0.9% (w/v) NaCl solution (control); 2) DXM (2 ml i.m. as a dose of 50 mug/kg body weight, every 12 h); 3) DXM plus gonadotropin releasing hormone (GnRH; 50 mug in 1 ml i.m. every 6 h); 4) 2 ml NaCl solution i.m. plus a single dose of 50 mug i.v. GnRH. Blood samples were collected twice daily from an indwelling jugular vein catheter for 3 d and at 15 min intervals for 12 h on the fourth day. DXM treatment resulted in lower (P M0.01) testosterone values in samples collected twice daily. More frequent sampling on Day 4 revealed that DXM reduced (P<0.01) the number of pulsatile increases of LH in plasma, although the individual mean pulse areas did not fiffer between the NaCl- and DXM-treated groups. This was associated with a decreased pulse frequency of testosterone (P<0.05). GnRH plus DXM treatment caused a significant elevation (P<0.05) in mean values as well as in the mean pulse area and in the total of the individual pulse areas of LH. Pulse area and mean concentrations of testosterone were also increased (P<0.01) when GnRH was given concurrently with DXM. Comparison of a single injection of GnRH when NaCl was being administered (Treatment 4) to one of the injections of GnRH (Day 4, 0800 h, Treatment 3) revealed a subsequently greater (P<0.01) pulse area in LH above base-line during DXM treatment (7.67 +/- 1.17 ng/ml) than during the NaCl (4.17 +/- 0.73 ng/ml) treatment period. This was reflected in a greater (P<0.01) pulse increase of testosterone following the LH pulse in boars treated with DXM. It is concluded that DXM treatment in the boar can reduce the pulse frequency of LH secretion, presumably by affecting GnRH secretion, but it has less effect directly on pituitary LH synthesis and release.

Fetal fluid steroids and their relationship to gonadal steroid secretion in single and twin bovine fetuses.

Steroid concentrations in the fetal fluids of 153 single and 69 twin bovine pregnancies, ranging in age from 35 to 125 d of gestation, were studied to compare gonadal steroid secretions in vitro with the concentrations found in amniotic and allantoic fluids during the early stages of sex differentiation. Among the steroids measured in fetal fluids, only the testosterone level showed a correlation with the amount secreted by the gonads. Significantly higher concentrations of testosterone were associated with male fetuses than with female fetuses. The concentrations of androstenedione, estradiol and estrone in both fetal fluid compartments were generally correlated with age, reflecting the extra-gonadal source of steroids in these fluids. Androstenedione levels in fetal fluids were significantly higher in twins than in singletons, suggesting that this parameter may be useful for the diagnosis of fetal sex and/or type of pregnancy.

Temporal changes in serum prostaglandin F2alpha and oxytocin in dairy cows with short luteal phases after the first postpartum ovulation.

Luteolysis in the cow depends upon an interaction between prostaglandin F2alpha (PGF2alpha) and oxytocin. The objectives of our study were 1) to determine oxytocin concentrations in postpartum dairy cows and 2) to identify the temporal relationship between oxytocin and PGF2alpha release patterns during luteolysis in normal and abbreviated estrous cycles in the postpartum period. Serum oxytocin and PGF2alpha metabolite (PGFM) concentrations from nine cows which had short estrous cycles (<17 d) were compared with those of six cows which had normal estrous cycles. Serum basal oxytocin concentrations in short estrous cycle cows (23.7 to 31.1 pg/ml) were higher (P<0.05) than those of normal estrous cycle cows (14.6 to 19.8 pg/ml). Oxytocin concentrations increased to peak values in both short and normal cycle cows, during luteolysis. Basal PGFM concentrations (112.2 to 137.4 pg/ml) were higher in cows with short cycle (P<0.05) than in cows with normal cycles (62.9 to 87.5 pg/ml). The increase in PGFM concentrations during luteolysis was significant in both normal cycle and short cycle cows (P<0.05). Increases in serum PGFM concentrations were always associated with increases in serum oxytocin concentrations in normal cycle and short cycle cows and the levels decreased simultaneously before the subsequent estrus. Results support the idea of a positive relationship between PGF2alpha and oxytocin concentration during the estrous cycle as well as a possible synergistic action of these hormones in the induction of luteolysis in dairy cattle.

Serum testosterone concentration in response to exogenous GnRH does not predict service rates or pregnancy rates by yearling, performance tested, crossbred bulls.

Ten bulls with a scrotal circumference of less than 30 cm at the end of growth performance testing, and 10 cohorts of the same age, size and breed type with a scrotal circumference greater than 30 cm were used to evaluate if testosterone response following GnRH administration could be used to test for fertility, for semen quality, and for specific pathologic testicular parenchymal changes. Serum testosterone concentrations were determined immediately before and 2 to 3 hours following intramuscular injection of 250 ug GnRH. Bulls were examined for breeding soundness, then fertility was tested in a breeding trial; testicular histology was assessed by determining the percentage of cross-sections of seminiferous tubules with no spermatocytes. The mean (+/-SEM) post-GnRH serum testosterone concentration for all bulls was 11.71 (+/-0.64) ng/ml. In order to examine for an association, the GnRH response was classified as above or below the mean for resultant serum testosterone concentration. The GnRH response classification was not related to the scrotal circumference, percentage of tubules devoid of spermatocytes, or percentage of progressively motile spermatozoa (P>0.10). The percentage of morphologically normal spermatozoa was significantly higher (P<0.05) in the bulls with a higher than mean testosterone secretion in response to GnRH injection. In the breeding trial, the percentage of heifers bred and the percentage of heifers pregnant (60 days post breeding) were not significantly different (P>0.10) between the 2 classifications of GnRH response. The GnRH response test was related to the percentage of morphologically normal spermatozoa but did not predict fertility of yearling bulls in this study.

Evaluation of the effect of GnRH on follicular ovarian cysts in dairy cows using trans-rectal ultrasonography.

The objectives of this study were to evaluate ovarian changes in cows with follicular ovarian cysts following treatment with either GnRH or saline. The parameters determined were the intervals from treatment to observation of a CL and from treatment to disappearance of the cyst, and the association between serum concentrations of LH, FSH and the LH/FSH ratio, before and after treatment, with the test intervals. Thirty-nine cows were identified as having follicular cysts. The GnRH treatment induced a significant increase in LH and the LH/FSH ratio. The gonadotropin response was not associated with the intervals from treatment to CL detection or to disappearance of the cyst. Survival curves for the intervals from treatment to CL detection and cyst disappearance indicate that treatment with GnRH or saline did not yield significantly different results for either parameter. The results question the efficacy of treating cystic ovarian disease with GnRH.

Hormonal control of estrous cyclicity and attempted superovulation in wood bison (Bison bison athabascae).

The wood bison (Bison bison athabascae) is a threatened Canadian species that has faced extinction twice in the last 100 yr. Development of assisted reproductive technologies could help ensure the long-term propagation and genetic management of this species. The objectives of this study were to refine estrus synchronization techniques and evaluate superovulatory responses after FSH or eCG administration. In Experiment 1, females were fitted with Syncro-mate B (SMB) implants for 9 d and received an injection of either estradiol valerate (E2V; n = 9) or cloprostenol (PGF; n = 9) at implant insertion (Day-9). In Experiment 2, estrus was synchronized with SMB implants and a PGF injection of Day-9, and superovulation was attempted on Day-2 with either 2500 IU eCG (n = 5) or 400 mg Folltropin-V (n = 5). In each experiment, biosin were examined daily for estrual behavior. Ultrasonography was used during the luteal phase to detect ovulation and assess ovarian status; feces were analyzed by ELISA for immunoreactive progestogens (P) to study ovarian endocrine responses. In Experiment 1, a closer synchrony of estrus was observed between Days 2 to 4 among the PGF-treated (77.8%) than the E2V-treated (66.7%) females. Corpora lutea (CL) were detected in 55% of E2V- and PGF-treated females. In Experiment 2, neither treatment successfully induced superovulation, with only a single female per treatment producing > or = 1 CL. In both experiments, progestogen profiles were similar for each treatment (P < 0.05).

Plasma progesterone levels in sows with induced cystic ovarian follicles.

Large multiple cystic ovarian follicles were induced in three sows and small multiple cystic ovarian follicles were induced in three other sows by injections of adrenocorticotrophic hormone (ACTH) during the follicular phase of the oestrous cycle. Plasma progesterone levels in sows with large cysts were relatively high, while those of sows with small cystic follicles were low. Removal of the ovaries with large cysts from one sow resulted in a precipitous drop in progesterone levels indicating that the large cysts were primarily the source of progesterone. The method by which ACTH may induced cystic ovaries was also investigated. Plasma progesterone levels in two ovariectomised sows during ACTH treatment fluctuated markedly during a 24 h period achieving peak values of 4 or 5 ng/ml. The results suggest that progesterone of adrenal cortical origin may be a factor in the development of the cystic ovarian condition.

Effect of the uterus on induced cystic ovarian follicles in the sow.

Large multiple cystic ovarian follicles were induced in 16 sows and small multiple cystic ovarian follicles were induced in five sows by daily injections of adrenocorticotrophic hormone during the follicular phase of the oestrous cycle. Large ovarian cysts persisted until euthanasia at 35 to 51 days after complete bilateral hysterectomy between days 5 and 10 in four sows. Atresia of large cysts was seen about days 15-18 in a sham-hysterectomy experiment. Unilateral hysterectomy of three sows resulted in persistence of large cysts on the ovary adjacent to uterine horn removal and atresia in the contralateral ovary. Lutein patches developed on the follicular wall of persistent cysts between the time of hysterectomy and autopsy. Atresia did not occur after hysterectomy in three sows with small cystic follicles, nor did sham hysterectomy of a sow with small ovarian cysts result in cyst atresia. A pronounced reduction in the size of large cysts occurred in three of four sows after the intrauterine injection of prostaglandin F2a. When a prostaglandin inhibitor, indomethacin, was injected into one uterine horn, the adjacent ovarian cysts persisted while those on the ovary next to the uterine horn receiving saline solution underwent atresia. Daily urinary oestrogen values from a hysterectomised sow with large cysts were initially high but subsequently fell to values between 30 and 60 microng/ml, except for several high values when signs of oestrus were observed. Oestrogen values in urine from a hysterectomised sow with small cysts were comparatively lower, and rose to high values only once in the 50-day period studied. Plasma oestrogen values in a hysterectomised sow with large cysts were high, although considerable day-to-day variation occurred. Plasma progesterone values were also high in this sow. In a sow with small cystic follicles for a 50-day period, oestrogen values in plasma were relatively low, but higher values were obtained occasionally. Plasma progesterone levels remained consistently low in this sow.

Half-life of 13,14-dihydro-15-keto prostaglandin f2 alpha in peripheral plasma of the pig.

The metabolite of prostaglandin F2 alpha (PGF2 alpha ) namely 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM), was administered as an intravenous bolus injection into five adult pigs. Concentrations of PGFM in blood collected periodically after injection indicated a biexponential decline suggesting a rapid distribution to the extracellular fluid and a slower elimination by metabolism. A mean half-life value of 14.97 +/- 1.33 (SD) minutes was calculated for the second component of the decline in PGFM concentration.

Prostaglandin F2 alpha and prolactin in experimental hypogalactia in sows.

Peripheral plasma concentrations of 13,14-dihydro-15-keto-prostaglandin F2alpha(PGFM), progesterone, prolactin and oestrone were determined in 20 sows for two days before and three weeks after parturition. Groups of four sows each received one of the following five treatments post partum: 30 ml sterile 0.9 per cent saline solution intrauterinely; ovariectomy and 30 ml saline solution intrauterinely; 10 ml Lugol's iodine plus 20 ml saline solution intrauterinely; ovariectomy and 10 ml Lugol's iodine plus 20 ml saline solution intrauterinely, or progesterone (0.5 mg [kg bodyweight]-1 intramuscularly). Saline solution and iodine were administered every 48 hours, starting immediately after parturition, for one week. Ovariectomy was performed within eight hours of delivery. Progesterone was given every third day for 12 days. Piglet weight gains were used as a reflection of milk yield. In all sows, oestrone values were elevated before parturition, but fell by the end of delivery and were very low during lactation. PGFM concentrations rose during the last two days of pregnancy to reach maximal values at the time of delivery. Plasma progesterone levels declined concomitantly with the rise in PGFM values before parturition. Basal values of progesterone were achieved within 24 hours after delivery in control sows receiving saline treatment. Progesterone values fell immediately after ovariectomy in sows receiving saline or iodine treatment but were slightly elevated for one week in sows that received only intrauterine iodine treatment, suggesting that complete regression of corpora lutea is prevented by suppression of post parturient uterine prostaglandin production. Sows injected with progesterone maintained plasma values of about 5 to 15 nmol litre-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma concentration profiles of gonadotrophins and testosterone in the adult boar.

Follicle stimulating hormone, luteinizing hormone and testosterone were measured by radioimmunoassay in plasma samples collected at 15 min intervals for a 12 h period in eight adult boars. Pulse increases in follicle stimulating hormone concentrations varied from one to four between individual boars while those of luteinizing hormone ranged from zero to four. The index of hormone production, provided by calculation of the area under the curve, was 0.5 +/- 0.51 microgram/L (means +/- S.D.) for follicle stimulating hormone and 0.46 +/- 0.11 microgram/L (means +/- S.D.) for luteinizing hormone. A significant correlation between changes in follicle stimulating hormone and luteinizing hormone values was seen in only two boars. The mean plasma testosterone concentration was 7.43 +/- 1.58 nM/L (means +/- S.D.). An identified increase in testosterone values occurred once in the 12 h period for six of the boars but was not noted in the other two animals. Although increases in testosterone could be identified with a previous pulse of luteinizing hormone, not all luteinizing hormone pulses were followed by an elevation in testosterone. A significant correlation between luteinizing hormone and testosterone was present in three of the eight animals. Follicle stimulating hormone and luteinizing hormone were measured in samples similarly collected two weeks after castration in the same eight boars. The number of pulses of follicle stimulating hormone increased significantly (p less than 0.05) and ranged from 3 to 7/12 h. The index of production of 1.8 +/- 1.15 micrograms/L (mean +/- S.D.) also represented a significant increase (p less than 0.05) over precastration follicle stimulating hormone values.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dexamethasone on gonadotrophin secretion in the gonadectomized sow and boar.

Saline solution or dexamethasone (DXM, 35 micrograms/kg bodyweight) was injected intramuscularly twice daily for four days into five ovariectomized sows and five castrated boars. Blood samples from an indwelling jugular vein catheter were taken at 15 min intervals for 12 h prior to DXM injection and on the fourth day of treatment in order to compare the effect on variables describing the pulsatile secretion of luteinizing hormone (LH) and follicle stimulating hormone (FSH). Dexamethasone treatment caused a decrease (p less than 0.05) in the number of pulsatile episodes of LH secretion in both gonadectomized boars and sows resulting in a significant decrease in mean concentrations. Follicle stimulating hormone secretion parameters appeared to be unaffected by DXM injection in both groups of animals. It is concluded that previously described differences in LH suppression in boars and sows given glucocorticoids may be attributed to the influence of gonadal hormones.

Morphometric and steroid hormone changes associated with experimental anovulatory follicles in the sow.

Steroid levels and ovarian follicular morphology were examined in sows on days 19 and 26 (day 5 of next cycle) after injection of adrenocorticotropic hormone (ACTH) or dexamethasone (DXM). Five sows received DXM (30 micrograms/kg bodyweight, intramuscularly) at 12 h intervals from days 9 to 14. Another five sows were given ACTH (2 IU/kg bodyweight, intramuscularly) from day 17 to day 19 or the end of estrus. Five control sows received no treatment. Ovulation occurred only in control sows and progesterone was significantly elevated at day 26. Estradiol values in ovarian vein blood were low but variable on day 19 in DXM- and ACTH-treated animals. Androstenedione values were lower (p less than 0.05) on both days in sows receiving DXM but not in those given ACTH compared to control values on day 19. Morphometric analysis, based on six follicles in each of three sows from each treatment group, indicated that follicular and antral diameters and granulosa cell numbers did not differ for either hormone treatment group on either day compared to those of control sows on day 19. The mitotic index suggested that cell replication continued. However, pyknotic and karyorrhectic nuclei were also seen in the hormone treatment groups. Follicles and oocytes from both DXM- and ACTH-treated sows showed signs of early degenerative changes including disorganization of cumulus cells and large lipid droplets in the cytoplasm of oocytes. Significant differences from control follicles in granulosa cell density and theca interna cell density suggested an association with the altered steroid hormone secretion.

Effect of cortisol on luteinizing hormone release during sexual behavior in the boar.

The effect of inhibiting the rise in cortisol concentrations that occurs at copulation upon luteinizing hormone release was studied in seven adult boars. Plasma samples were collected for assay of luteinizing hormone, testosterone and cortisol on a control day and before, during and after exposure to an estrous sow. The area under the curve was used to evaluate hormone production and treatment effects were evaluated by a paired Student's t-test. The 11 beta-hydroxylase inhibitor, metyrapone, was used to suppress glucocorticoid hormone production. Cortisol concentrations increased significantly (p less than 0.05) after breeding compared to values on the control day while treatment with metyrapone prior to breeding prevented the cortisol increase (p greater than 0.05). Although luteinizing hormone production increased significantly after copulation in both breeding experiments, metyrapone pretreatment resulted in a reduction of luteinizing hormone secretion (p less than 0.05). Testosterone production was also reduced in boars pretreated with metyrapone. The results suggest that the increased levels of cortisol occurring at copulation may enhance luteinizing hormone release in boars.