Peroxisomal chain-shortening of prostaglandin F2 alpha

We have recently reported that prostaglandin F2 alpha can be chain-shortened by isolated rat liver peroxisomes. In the present study it is further established by cell fractionation experiments that the enzymes involved in this reaction are localized to peroxisomes. Under the conditions employed, the highest activity was found in the light mitochondrial fraction. Further fractionation of the light mitochondrial fraction by sucrose density gradient centrifugation showed that the prostaglandin oxidation activity comigrated with peroxisomal marker enzymes. Di(2-ethylhexyl)phthalate treatment resulted in a tenfold increased capacity for the conversion of prostaglandin F2 alpha into tetranorprostaglandin F1 alpha. The reaction was not inhibited by KCN. The reaction was further characterized with respect to cofactor requirements. The prostaglandin oxidation was found to be completely dependent on NAD, CoA, ATP, Mg2+ and was stimulated by FAD. Incubation of prostaglandin E2 with peroxisomes resulted in conversion into several products. After alkaline hydrolysis, one of these was identified as tetranorprostaglandin B1.     

Effect of prostaglandin F3 alpha on gastric mucosal injury by ethanol in rats: comparison with prostaglandin F2 alpha

In humans eicosapentaenoic acid can be converted to 3-series prostaglandins (PGF3 alpha, PGI3, and PGE3). Whether 3-series prostaglandins can protect the gastric mucosa from injury as effectively as their 2-series analogs is unknown. Therefore, we compared the protective effects of PGF3 alpha and PGF2 alpha against gross and microscopic gastric mucosal injury in rats. Animals received a subcutaneous injection of either PGF3 alpha or PGF2 alpha in doses ranging from 0 (vehicle) to 16.8 mumol/kg and 30 min later they received intragastric administration of 1 ml of absolute ethanol. Whether mucosal injury was assessed 60 min or 5 min after ethanol, PGF3 alpha was significantly less protective against ethanol-induced damage than PGF2 alpha. These findings indicate that the presence of a third double bond in the prostaglandin F molecule between carbons 17 and 18 markedly reduces the protective effects of this prostaglandin on the gastric mucosa.     

Postpartum subestrus in dairy cows: comparison of treatment with prostaglandin F2 alpha or GnRH + prostaglandin F2 alpha + GnRH

Two experiments (Experiment 1, 185 cows in 1996/97; Experiment 2, 168 cows in 1997/98) were conducted with Prim Holstein dairy cattle in the Mayenne region of France to investigate subestrus. Cows which had not been observed in estrus since calving were allocated alternately to treatment groups between 60 and 90 d post partum as follows: Experiment 1-Group 1: GnRH (Day 0, 100 micrograms i.m.), PGF2 alpha (Day 7, 25 mg i.m.), GnRH (Day 9, 100 micrograms i.m.) and AI (Day 10); Group 2: PGF2 alpha (Day 0, 25 mg i.m.), AI at estrus, or, if estrus was not observed, a second PGF2 alpha injection on Day 13, and AI on Day 16 and Day 17. Treatments in Experiment 2 were as follows: Group 1: as Experiment 1-Group 1 but AI at the observed estrus after Day 0, or at Day 10 if estrus was not observed; Group 2: as Experiment 1--Group 2, however, if a second PGF2 alpha injection was given on Day 13, AI at the observed estrus. Progesterone was measured in serum at Day 0 and in milk at AI. Pregnancy diagnosis was performed by measuring bovine pregnancy-specific protein B (bPSPB; Day 50 +/- 3) and confirmed by ultrasonography when the result was doubtful. In Experiment 1, farmers observed 47/101 (46.9%) Group 1 cows in estrus, 33/91 cows on Day 10 and 10 cows before Day 10. The progesterone concentrations were compatible with estrus in 69/86 (80%) cows on Day 10. In Group 2, 36/83 (43.4%) cows were inseminated after the first PGF2 alpha injection. After the second PGF2 alpha injection, only 29/43 (67%) cows had a low progesterone concentration at AI. Pregnancy rates were 36.1 and 32.5% for Groups 1 and 2, respectively. In Experiment 2, estrus was observed in 31/93 (33.7%) Group 1 cows. In Group 2, 51/75 (66%) cows were inseminated after the first injection of PGF2 alpha, 13/75 (17.3%) cows after the second injection, while 11/75 (14.7%) were not observed in estrus. Pregnancy rates were 53.7 and 53.3% in Groups 1 and 2, respectively. In conclusion, it is recommended that subestrus be treated with PGF2 alpha followed by AI at the observed estrus when estrus detection is good, while the use of GnRH + PGF2 alpha + GnRH is recommended when estrus detection is poor.     

Role of prostaglandin F2alpha in ovulation.

Using radioimmunoassay procedures, the levels of plasma, uterine and ovarian prostaglandin (PG) F2alpha, and those of plasma estradiol and progesterone were measured in intact, hysterectomized or ovariectomized immature female rats pretreated with PMS and subsequent HCG. Occurrence of ovulation was confirmed at 8 hours after the HCG administration not only in the intact rats but also in the hysterectomzied rats. The levels of plasma estradiol and progesterone, and of uterine and ovarian PGF2alpha rose with the PMS injection alone, but they did not reach the peaks before the HCG administration. Both plasma estradiol and uterine PGF2alpha showed a peak at 2 hours after the HCG injection. These peaks were antecedent 2 or 6 hours before the peaks of ovarian and plasma PGF2alpha, respectively. However, such increase of uterine PGF2alpha does not seem to be indispensable for ovulation, because ovulation could occur in the hysterectomized rats. The levels of ovarian PGF2alpha showed a high plateau from 4 to 8 hours after the HCG injection, and then rapidly decreased after ovulation. The levels of plasma PGF2alpha peaked not only in the intact rats but also in the hysterectomized rats at 8 hours after the HCG treatment. But in the ovariectomized rats, this plasma PGF2alpha peak at 8 hours disappeared and there was no statistical change of plasma PGF2alpha throughout the PMS-HCG treatment. Plasma progesterone gradually increased and reached the maximum at 10 hours after the HCG injection. These results conclude that the main source of increased plasma PGF2alpha during the ovulatory process induced with the PMS-HCG treatment is the ovary, and it is strongly suggested that a rapid increase of PGF2alpha in the ovary may play some important role(s) in the ovulatory process.     

Urinary excretion of prostaglandin E2 and prostaglandin F2alpha in potassium-deficient rats

Potassium-deficiency was induced in rats by dietary deprivation of potassium. The animals became polyuric and urine osmolality decreased more then three-fold compared to controls. Urinary excretion of prostaglandin E2 (PGE2) and prostaglandin F2alpha (PGF2alpha) did not increase during 2 weeks of potassium depletion. Partial inhibition of renal prostaglandin synthesis by meclofenamate did not increase the urine osmolality after water deprivation. These results make unlikely the hypothesis that the polyuria of potassium-deficiency, is the result of enhanced renal synthesis of prostaglandins with subsequent antagonism of the hydro-osmotic effect of vasopressin. Male animals consistently excreted less PGE2 than female animals.     

Treatment with prostaglandin F2alpha increases expression of prostaglandin synthase-2 in the rat corpus luteum

Recent studies indicate that the corpus luteum (CL) may be a source of prostaglandin F2alpha (PGF2alpha) for regression. We investigated expression of mRNA and protein for prostaglandin G/H synthase (PGHS) in the CL of immature superovulated rats following administration of PGF2alpha. We observed an increase in mRNA for PGHS-2, the induced isoform, at 1 h and protein at 8 and 24 h after treatment. One hour after PGF2alpha, there was also a progressive decrease in plasma progesterone concentration. There were no changes, however, in expression of PGHS-1, the constitutive isoform, over the 24 h sampling period. These results indicate that PGHS-2 increases following PGF2alpha treatment and that expression of this enzyme in the rat CL may contribute to the luteolytic mechanism.     

Effects of indomethacin, prostaglandin E2, prostaglandin F2 alpha and 6-keto-prostaglandin F1 alpha on hatching of mouse blastocysts

The present study has been performed to investigate how PGs would participate the hatching process. Effects of indomethacin, an antagonist to PGs biosynthesis, on the hatching of mouse blastocysts were examined in vitro. Furthermore, it was studied that prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha) or 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) were added to the culture media with indomethacin. The hatching was inhibited by indomethacin yet the inhibition was reversible. In the groups with indomethacin and PGE2, no improvement was seen in the inhibition of hatching and the inhibition was irreversible. In the groups with indomethacin and PGF2 alpha, inhibition of hatching was improved in comparison with the group with indomethacin. In the groups with indomethacin and 6-keto-PGF1 alpha, no improvement was seen. The above results indicated that PGF2 alpha possibly had an accelerating effect on hatching and a high concentration of PGE2 would exert cytotoxic effect on blastocysts.     

Histophysiological studies of prostaglandin F2alpha on isolated organs. I. Effect of prostaglandin F2alpha on the heart.

The physiological and histochemical effects of PGF2alpha on isolated rabbit hearts were examined. The results showed a positive inotropic effect. The coronary flow increased. From the histochemical studies, adenosine triphosphatase (ATP-ase) and succinic dehydrogenase activities were increased while that of alkaline phosphatase was decreased. Glycogen granules were depleted. These findings were discussed on a histophysiological basis.     

Mid-trimester abortion with 15 (S) methyl prostaglandin F 2 alpha

The efficacy of intramuscular administration of 15 methyl (15S) prostaglandin F2alpha (PGF2a) in midtrimester pregnancy termination was evaluated in 16 healthy patients (mean age, 23.3; mean parity, 1.4; mean number of menstrual weeks, 16.1) by measuring dose response; oxytocin conversion; abortion time; side effects; intrauterine dynamics and progesterone withdrawal. Labor was monitored using extraovular balloon placed transvaginally; transcervically; and connected to a Physiograph machine. Patients not aborting within 48 hours after the first dose were considered failures. Blood samples were collected at 0, 3, and 6 hours and at abortion time for plasma progesterone measurement. Average dose given was 789 +or- 60 micrograms. Only 9 of 10 patients aborted within the prescribed 48 hours: 7 were complete abortions, and 2 were incomplete and required suction curettage. Mean induction to abortion time was 20.2 +or- 2.7 hours. Nausea, vomiting and diarrhea were the main side effects. The findings suggest that 15 methyl PGF2a in the dosages and routes prescribed is not as efficient as PGF2a. It is also suggested that prostaglandin affects the myometrium at 2 levels: 1) a membrane effect, and 2) a more fundamental intracellular regulatory effect which is necessary to initiate labor.     

Mid-trimester abortion with intra-amniotic prostaglandin F2 alpha and intravenous oxytocin infusion

Induction of abortion in mid-trimester pregnancies were performed on 26 patients. The first 12 patients were treated by intra-amniotic instillation of Prostaglandin F2 alpha, with a mean dosage of 40.2 mg. and mean abortion time of 24 hours and 41 minutes (ten patients). Fourteen additional mid-trimester abortions were performed using identical protocol plus the addition of oxytocin by intravenous infusion two hours after injection of the prostaglandin. All patients aborted, with mean dosage of PGF2 alpha of 28.2 mg. and mean abortion time of 15 hours and 37 minutes.     

Chain-shortening of prostaglandin F2 alpha by rat liver peroxisomes

Liver peroxisomes were isolated from di(2-ethylhexyl)phthalate treated rats by isopycnic sucrose gradient centrifugation of a light mitochondrial fraction. Incubation of prostaglandin F2 alpha with purified peroxisomes resulted in conversion into a more polar product(s). In contrast, incubation with mitochondrial fractions and microsomal fractions under the same conditions did not result in any detectable conversion. The polar material obtained from a preparative incubation was purified by high performance liquid chromatography and characterized by radio-gas chromatography and gas chromatography-mass spectrometry. The structure of the polar compound was shown to be 5,7,11-trihydroxy-tetranorprost-9-enoic acid (tetranor-prostaglandin F1 alpha). Prostaglandin F2 alpha was thus chain-shortened by four carbon atoms.