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Biomedical subjects

L L Espey

Publications and source records attributed to L L Espey.

At least 37 records · Page 2Linked to original sources
PubMed1989

Effect of indomethacin, cycloheximide, and aminoglutethimide on ovarian steroid and prostanoid levels during ovulation in the gonadotropin-primed immature rat.

It has become popular to use the gonadotropin-primed immature rat to study ovulation. The ovarian content of progesterone, estradiol, PGE2, PGF2 alpha, and 6-keto-PGF1 alpha during the ovulatory process was determined in this model. Also, the effect of three anti-ovulatory agents on the ovarian levels of the above substances was determined. At 23 days of age, Wistar rats were primed with pregnant mares serum gonadotropin (PMSG) sc, and two days later the ovulatory process was initiated with human chorionic gonadotropin (hCG) sc. The ovarian follicles began rupturing 12 h later. Ovaries were assayed for the two steroids and prostanoids at 2-h intervals before and several 4-h intervals after ovulation. The ovarian estradiol level increased slightly between 0 and 2 h after hCG, while the progesterone level increased sharply between 2 and 4 h after hCG--at a time when the estradiol declined markedly. All three prostanoids increased concomitantly with progesterone. When the PG synthesis was blocked by indomethacin treatment at 1 h before hCG, ovarian progesterone levels still increased. In contrast, when steroidogenic activity was inhibited by aminoglutethimide, the ovarian prostanoid levels also decreased. Cycloheximide had little effect on the steroids and prostanoids. It is concluded that ovarian prostanoid synthesis might be influenced by ovarian steroid output.

Aminoglutethimide↗
PubMed1989

Increase in ovarian blood volume during ovulation in the gonadotropin-primed immature rat.

This study quantifies ovarian blood volume in Wistar rats by measuring the optical density (414 nm) of hemoglobin in ovarian extracts and comparing this measurement to the optical density of known amounts of whole blood. Immature rats were primed with pregnant mare's serum gonadotropin (PMSG), 10 IU s.c., at 23 days of age. On Day 25, the ovulatory process was initiated by human chorionic gonadotropin (hCG), 10 IU s.c., and ova began to appear in the oviducts 10 h later. At 2-h intervals, the ovaries were extirpated and homogenized in 1.0 ml of 0.05 M tris (hydroxymethyl)aminomethane buffer (pH 7.4) for 30 s. Homogenates were centrifuged for 20 min and the supernatant fluids were analyzed with a Gilford RESPONSE UV/VIS spectrophotometer. The hemoglobin in these ovarian extracts had the same peak absorbance of 414 nm characteristic of oxyhemoglobin in whole blood taken by cardiac puncture of the rats. There was a linear relationship between the absorbance and the volume of whole blood in the samples. The volume of blood per ovary from groups of 8 rats was 0.60 +/- 0.07 microL at 0 h after hCG. The volume increased to 1.37 +/- 0.26 microL at 4 h after hCG and reached a peak of 4.55 +/- 0.72 microL at 10 h. Indomethacin treatment (0.3-10.0 mg/rat, s.c.) partially inhibited this 7-fold increase in ovarian blood volume. In conclusion, the increase in ovarian blood volume during ovulation may reflect the vasodilation and hyperemia that are characteristic of inflamed tissues.

Animals↗
PubMed1989

Decrease in ovarian platelet-activating factor during ovulation in the gonadotropin-primed immature rat.

Platelet-activating factor (PAF) is a biologically active phospholipid that is released locally during acute inflammatory reactions and tissue injury. Since there is evidence that the biochemical events of mammalian ovulation resemble an inflammatory reaction, the objective of this study was to determine whether ovarian levels of PAF change during ovulation. At 2-h intervals during the ovulatory process in gonadotropin-primed 25-day-old Wistar rats, the ovaries were extirpated, homogenized, and extracted for lipids. The extracts were subjected to thin-layer chromatography (TLC), and the portion of the silica gel that comigrated with PAF was re-extracted and assayed for PAF activity. The PAF was measured (in fmole equivalents of synthetic PAF) by a bioassay based on the capacity of aliquots of the extracts to release [3H]-serotonin from platelets isolated from whole blood of rabbits and prelabeled with [3H]-serotonin. The ovarian level of PAF decreased (p less than 0.01) by 36% from 6.67 +/- 0.77 to 4.27 +/- 0.45 fmoles/mg ovary by 2 h after treatment with human chorionic gonadotropin (hCG), and it declined another 14% by 4 h after hCG. The ovarian PAF remained at this reduced level for up to 24 h after hCG. The administration of indomethacin (5 mg/rat, s.c.) or epostane (5 mg/rat, s.c.) at 1 h after hCG prevented ovulation, but neither drug affected the decline in ovarian PAF. Preliminary tests showed that the lipid extracts from the ovaries also contained PAF inhibitor(s) that comigrated with PAF on the TLC plates. Similar to PAF, the lipid-soluble inhibitor(s) decreased (p less than 0.05) in the ovaries within 4 h after hCG treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Androstenols↗
PubMed1989

Increase in ovarian leukotrienes during hormonally induced ovulation in the rat.

The ovulatory process was initiated in 25-day-old Wistar rats by injecting human chorionic gonadotropin (hCG; 10 IU sc) 2 days after the animals had been primed with pregnant mares serum gonadotropin (PMSG; 10 IU sc). By 4 h into the ovulatory process, leukotriene (LT) B4 increased 2-fold (P less than 0.001) and LTs C4/D4/E4 increased 1.3-fold (P less than 0.002). By the time of ovulation (10-12 h after the administration of hCG) both eicosanoids declined to their pre-hCG levels. When animals were treated with the cyclooxygenase inhibitor indomethacin at the specific dose of 0.316 mg/rat sc at 1 h before hCG, the ovarian levels of LT B4 and LTs C4/D4/E4 increased to 210% (P less than 0.01) and 113% (P less than 0.05), respectively, above the control levels at 4 h after hCG. Concomitantly, this dosage of indomethacin reduced ovarian prostaglandins (PGs) E and F by 99% (P less than 0.001) and 98% (P less than 0.001), respectively, and it reduced the ovulation rate by 76% (P less than 0.001). Thus it appears this dose of indomethacin blocked the conversion of ovarian arachidonic acid into PGs and shunted this substrate into the lipoxygenase pathways that lead to LT formation. In conclusion, the moderate increase in ovarian LTs is characteristic of inflammatory reactions, and, therefore, these data support the hypothesis that the biochemical events of ovulation resemble an inflammatory process.

Animals↗
PubMed1989

Increase in ovarian 15-hydroxyeicosatetraenoic acid during ovulation in the gonadotropin-primed immature rat.

The ovarian level of 15-hydroxyeicosatetraenoic acid (15-HETE) was measured by RIA during ovulation in gonadotropin-primed immature Wistar rats. The ovulatory process was initiated in 25-day-old rats by a 10-IU injection of hCG sc 2 days after the animals had been primed with 10 IU PMSG, sc. Ovarian follicles begin to ovulate 10 h after hCG. At 0 h after hCG, the ovarian 15-HETE level was 0.6 +/- 0.2 ng/mg ovarian protein. At 6 h the 15-HETE level increased sharply to 27.3 +/- 4.2 ng/mg protein and reached a peak of 50.0 +/- 9.8 ng/mg protein at 10 h. Ovarian 15-HETE decreased significantly between 10-16 h after hCG (when ovulation was essentially completed). The pattern of secretion of this 15-lipoxygenase product was reciprocal to the pattern of secretion of leukotriene-B4 by the rat ovary. Ovarian 15-HETE production and ovulation were inhibited in a dose-dependent manner when indomethacin was administered sc 1 h after hCG in doses ranging from 0.10-10.0 mg/rat. In contrast, the synthesis of ovarian prostaglandins-E and -F was inhibited by a dose of indomethacin as low as 0.0316 mg/rat, but this dose did not significantly affect the ovarian 15-HETE level or the ovulation rate. Therefore, the ovulation rate was more closely correlated with the ovarian 15-HETE level (P less than 0.001) than with the ovarian levels of either prostaglandin-E or -F (0.10 greater than P greater than 0.05). The results suggest that products of the 15-lipoxygenase pathway of arachidonic acid metabolism may be important in the biochemical events of mammalian ovulation.

Animals↗
PubMed1989

Increase in ovarian kallikrein activity during ovulation in the gonadotrophin-primed immature rat.

The ovulatory process was initiated in 25-day-old rats by injecting them with hCG (10 i.u., s.c.) 2 days after the animals had been primed with PMSG (10 i.u., s.c.). At 2-h intervals after hCG, the ovaries were extracted and assayed for glandular kallikrein activity by using a chromogenic substrate (H-D-Val-Leu-Arg-p-nitroanilide) which exhibits optical density (at 405 nm) upon hydrolysis. In 0-h control ovaries the activity was 12.5 x 10(-3) kallikrein units (KU)/mg protein and it increased to a peak of 56.6 x 10(-3) KU/mg at 12 h after hCG, when the follicles first began to rupture. The kallikrein activity was distinguishable from ovarian plasminogen activator activity on the basis of pH optima and response to trypsin inhibitor (SBTI). The activity was inhibited by a s.c. dose of indomethacin of 0.3 mg/rat, or higher, and this dosage inhibited ovulation. The results suggest that kallikrein activity contributes to the degradation of Graafian follicles during ovulation in mammals.

Animals↗
PubMed1989

Pattern of ovarian steroid secretion during ovulation of in vitro perfused rat ovaries varies with method of sampling.

Wistar rats were primed at 25 days of age with 20 i.u. PMSG s.c., followed 48 h later with 100 ng LH/ml to induce the ovulatory process in vitro. Assays for progesterone, oestradiol, and testosterone were performed on samples taken at fixed intervals of 0, 1, 2, 4, 8 and 12 h after LH administration. The results show that, while there was some degree of correlation in the concentrations of progesterone between the ovarian extract and perfusate, there were very large differences in the measurable amounts of testosterone and oestrogen in the fluid samples and ovarian homogenates. Therefore, taking samples from the perfusate may not provide a good assessment of the steroidogenic activity in the ovary.

Animals↗
PubMed1988

Rat ovarian prostaglandin levels and ovulation as indicators of the strength of non-steroidal anti-inflammatory drugs.

Immature Wistar rats were treated with pregnant mare's serum gonadotropin and human chorionic gonadotropin to induce ovulation. The non-steroidal anti-inflammatory drugs indomethacin, diclofenac, flurbiprofen, and phenylbutazone inhibited both the ovulation rate and the normal increase in ovarian prostaglandin E during ovulation. Tolmetin, ibuprofen, and aspirin did not have any significant effect. There was a significant correlation between the ovulation rate and the level of ovarian prostaglandin E following treatment with these drugs. When indomethacin was given in graded doses, there was also a correlation between ovulation rate and the dose-dependent inhibition of ovarian prostaglandin E.

Animals↗
PubMed1986

Ovarian increase in kinin-generating capacity in PMSG/hCG-primed immature rat.

Ovarian kinin-generating capacity was determined during induced ovulation in immature Wistar rats. The onset of ovulation was monitored by counting the number of ova in the oviducts at 2-h intervals after the administration of human chorionic gonadotropin (hCG). Ova began to appear in significant numbers at 14 h after hCG, with an average of 7.6 +/- 2.3 ova/rat. By 16 h after hCG, the oviducts contained 32.7 +/- 4.1 ova/rat. The ovaries from each group of animals were homogenized in phosphate-buffered saline, and extracts of this tissue were incubated for 200 min to allow the generation of kinins from endogenous kininogen. The amount of kinin generated by this procedure was measured by radioimmunoassay. At 0 h (i.e., just before the administration of hCG), the ovaries contained 5.90 +/- 0.60 pg kinin/micrograms protein per 200 min in the ovarian extract. By 4 h after hCG, the kinins increased significantly (P less than 0.05) to 13.16 +/- 3.61 pg kinin/micrograms protein. The kinins progressively increased (P less than 0.001) to 67.88 +/- 23.26 pg kinin/micrograms protein by 16 h after hCG. Indomethacin and cycloheximide significantly inhibited both kinin-generating activity and ovulation. These data suggest that kinin-forming activity and kinins may have a role in the ovulatory process of mammals.

Animals↗
PubMed1986

Effect of time and dose of indomethacin on follicular prostaglandins and ovulation in the rabbit.

This study determined specifically when ovarian prostaglandins (PGs) increase during ovulation and how effectively different doses of indomethacin inhibit PGs and ovulation. Rabbit ovarian follicles were removed at hourly intervals after stimulating the animals with hCG (50 IU/kg). The follicles were homogenized in 0.1 M acetate buffer (pH 4.5), and the PGE and PGF in the extracts were measured by RIA. Ovulation rates were determined by calculating the percentage of mature follicles that ruptured after stimulation by hCG. Before hCG, the normal levels of PGE and PGF were 111.1 +/- 14.7 and 51.0 +/- 6.6 pg/mg follicle, respectively. By 2 h after hCG treatment, PGE and PGF both increased to 162.6 +/- 17.0 and 80.6 +/- 13.3 pg/mg follicle, respectively. Approximately 5 h later, there was a second, sharper increase in both PGs which peaked at 652.6 +/- 63.5 and 345.4 +/- 32.3 pg/mg follicle, respectively, 10 h after hCG treatment, i.e. at the expected time of ovulation. We found that regardless of whether indomethacin was given early or late during the ovulation process, this agent significantly reduced follicular PG production within 5 min after its administration. For example, only 5 min after 10 mg/kg indomethacin were administered 8 h after hCG, PGE and PGF dropped from 317.7 +/- 50.0 and 125.0 +/- 10.5 pg/mg follicle to 93.3 +/- 17.4 and 49.3 +/- 10.5 pg/mg follicle, respectively. Unexpectedly, when graded doses of indomethacin were administered either 1 or 8 h after hCG, there was not a statistically significant correlation between follicular PG levels and ovulation rate. For example, when doses of 1.25, 2.5, 5.0, and 10.0 mg/kg indomethacin were given 8 h after hCG, the PGE and PGF levels at the expected time of ovulation (i.e. 2 h later) were always equal to or less than the PG levels in follicles that had not been stimulated by hCG, yet ovulation proceeded at rates of 46.7 +/- 12.3%, 30 +/- 7.7%, 14.3 +/- 9.3%, and 0%, respectively. Therefore, the results raise questions about the specific role of PGs in the ovulation process.

Animals↗
PubMed1986

Cycloheximide inhibition of ovulation, prostaglandin biosynthesis and steroidogenesis in rabbit ovarian follicles.

Cycloheximide (5 mg/kg, i.v.) significantly inhibited ovulation in the rabbit when it was administered as early as 20 h before the ovulation process was initiated by hCG, and as late as 1 h after hCG. The ovulation rate was significantly reduced, but follicular biosynthesis of prostaglandins E and F was only partly inhibited. The biosynthesis of progesterone and oestradiol in follicles during the early stages of the ovulation process was also inhibited. Cycloheximide may therefore inhibit ovulation by a mechanism which is different from the action of indomethacin, and this mechanism may involve the suppression of ovarian steroidogenesis.

Animals↗
PubMed1985

Increase in plasminogen activator in the involuting uterus of the postpartum rat.

Plasminogen activator (PA) activity in the rat uterus was measured at fixed intervals post partum in order to determine whether this serine protease increases during the acute remodelling of tissue which occurs in the involuting uterus. Plasminogen activator activity was measured by an indirect method based on the hydrolysis of the chromogenic substrate S-2251 by PA-generated plasmin. At the time of parturition the control level of PA activity was 0.033 +/- 0.018 (S.D.) mumol/4 mg uterine wet weight per 30 min. This activity increased fourfold to a peak of 0.131 +/- 0.036 at 3 days post partum, and then it declined steadily towards the control level during the next 7 days. Concomitantly, uterine weight decreased to 25% of the control weight by 3 days post partum, and it continued to decrease until day 15. In the 30 days post partum during which PA activity was monitored there was no significant change in plasmin inhibitors in the uterine extracts. The results suggest a correlation between PA activity and the process of tissue remodelling which occurs during involution of the rat uterus. This increase in PA might serve to activate a latent collagenase since the measured peak in PA activity happens to coincide with a reported increase in collagenolytic activity in the involuting rat uterus.

Animals↗
PubMed1983

Comparison of the effect of nonsteroidal and steroidal antiinflammatory agents on prostaglandin production during ovulation in the rabbit.

The nonsteroidal antiinflammatory agents diclofenac, fenoprofen and aspirin were tested to determine how well they inhibit the preovulatory elevation in prostaglandin (PG) production in rabbit follicles in comparison to indomethacin. In addition, the steroidal antiinflammatory agent dexamethasone and the antipyretic agent acetaminophen were tested. The agents were administered 8 h after the ovulatory process was stimulated by hCG (50 I.U./kg). At 10 h after hCG (i.e., at the expected time of ovulation) control follicles had PGF and PGE levels of 370.0 and 582.6 pg/mg of follicle, respectively. Diclofenac inhibited PG production the most--reducing PGF and PGE to 22.8 and 53.6 pg/mg, respectively. Indomethacin reduced the PGF and PGE levels to 27.4 and 76.6 pg/mg, respectively. Fenoprofen was less effective, reducing the PGF and PGE to 77.8 and 222.4 pg/mg, respectively. Aspirin reduced the PGF and PGE to 123.4 and 174.6 pg/mg, respectively. Dexamethasone and acetaminophen did not inhibit PG production. Ovulation was completely inhibited by diclofenac and indomethacin, partially inhibited by fenoprofen, and unaffected by aspirin, acetaminophen, or dexamethasone. The results suggest that any potent nonsteroidal antiinflammatory agent can inhibit ovulation provided it adequately reduces PG production; whereas steroidal antiinflammatory agents are ineffective. The antiinflammatory agent must completely abolish the preovulatory elevation in PGs in mature follicles in order to totally inhibit ovulation.

Acetaminophen↗
PubMed1983

Inhibition of ovulation in the rabbit by the antimitotic agent, colchicine.

This study establishes the optimum time to administer colchicine to inhibit ovulation in the rabbit, and it examines the effect of colchicine on prostaglandin biosynthesis in ovulatory follicles. Colchicine (2 mg/kg) was given at intervals ranging from 50 hours to 2 hours before ovulation. The ovulation efficiency was significantly reduced when colchicine was administered between 30 hours and 9 hours before ovulation, with maximum inhibition occurring at 20 hours before ovulation. Normal elevation in prostaglandin biosynthesis at the time of ovulation was significantly reduced when colchicine was given at 20 hours before ovulation, but not when it was given at 9 hours or 2 hours before ovulation. The results suggest that the mechanism by which the antimitotic agent colchicine inhibits prostaglandin biosynthesis and ovulation may be different from that of the nonsteroidal antiinflammatory agent indomethacin.

Animals↗
PubMed1982

Optimum time for administration of indomethacin to inhibit ovulation in the rabbit.

The antiinflammatory agent, indomethacin, inhibits ovulation in mammals by interfering with the synthesis of prostaglandins in preovulatory follicles. To determine the optimum time to administer this inhibitor, indomethacin was given at specific intervals from 10 h before, and up to 9 h after, the ovulatory process had been initiated by hCG (50 I.U./kg). The drug dosage ranged from 1.25 mg/kg to 40 mg/kg. The optimum time to give indomethacin was at 7-8 h after hCG (i.e., 2-3 h before expected rupture of the follicle) at which time the minimum effective dose was 2.5 mg/kg. Since a significant elevation in prostaglandin synthesis occurs as early as 3-5 h after hCG stimulation of rabbit follicles (1), these results reveal that nonsteroidal antiinflammatory agents can interrupt the ovulatory process even after the follicle has begun producing substantial amounts of prostaglandins. The data suggest that prostaglandins need to be produced continuously in the follicle up to the time of actual rupture or else that indomethacin is interfering with some other aspect of the ovulatory process which transpires after the elevation of prostaglandins.

Animals↗
PubMed1982

Survey of antiinflammatory agents and related drugs as inhibitors of ovulation in the rabbit.

A wide variety of antiinflammatory agents and related compounds were administered to rabbits so that their ability to inhibit ovulation could be evaluated. In order of decreasing effectiveness, ovulation was inhibited by the nonsteroidal antiinflammatory agents diclofenac, indomethacin, fenoprofen, niflumate, tolmetin, phenylbutazone, naproxen, meclofenamate, ibuprofen, and flufenamate. Ovulation was not inhibited by aspirin, salicylate, or mefenamate, nor by the steroidal antiinflammatory agents dexamethasone (DEX) and prednisolone. The antineoplastic agents colchicine and vinblastine inhibited ovulation, but not azathioprine, 6-mercaptopurine, or cyclophosphamide. Contrary to previous reports, ovulation was not inhibited by the antihistamines chlorpheniramine, diphenhydramine, or cimetidine. Among the miscellaneous agents tested, ovulation was strongly inhibited by cycloheximide and slightly by acetaminophen but not by clomiphene, quinacrine, allopurinol, diethylstilbestrol (DES), heparin, melatonin, papaverine, chloroquine, D-penicillamine, or levamisole. These results show that ovulation can be inhibited by agents that inhibit acute inflammatory reactions.

Animals↗
PubMed1981

Effect of indomethacin on preovulatory changes in the ultrastructure of rabbit Graafian follicles.

This investigation uses electron microscopy to examine the effect of prostaglandins on follicular tissue during the ovulatory process. The ultrastructure of follicles from indomethacin-treated rabbits was compared to the ultrastructure of normal ovulatory follicles in order to determine the morphological differences between follicles with negligible and normal prostaglandin synthesis, respectively. The most obvious difference between the two groups of follicles was that the tissue at the apex of normal follicles began to thin out significantly by 9 h post coitus (near the time of ovulation), whereas the follicles from indomethacin-treated animals showed no signs of thinning, even as late as 12 h post coitus. It appeared that the fibroblasts in the follicles with limited prostaglandin synthesis failed to undergo the normal ovulatory transformation from a quiescent to a proliferative state. Otherwise, the prostaglandin-deficient follicles had a number of morphological features similar to those which usually occur in ovulatory tissue. There was detectable loosening of the connective tissue elements and some indication of edema at the apex of the mature follicles. Also, granulocytes became localized in the vascular compartment of these follicles. In addition, there tended to be an increase in the multivesicular structures which protrude from the fibroblasts, as well as an increase in the dense granules which accumulate in the cytoplasm of the surface epithelial cells. Collectively, these data suggest that normal prostaglandin synthesis in ovulatory follicles may be important in the connective tissue decomposition and ultimate thinning of the follicle wall.

Animals↗