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Biomedical subjects

M J Harper

Publications and source records attributed to M J Harper.

At least 91 records · Page 5Linked to original sources

Preparation of smooth muscle cell suspensions from the rabbit oviduct and prostaglandin binding analysis.

The preparation, viability, and prostaglandin (PG) binding characteristics of dispersed smooth muscle cells from the rabbit oviduct have been determined. Cell suspensions were prepared by enzymatic degradation of the intracellular matrix and subsequent mechanical dispersion with a wide bore pipette. The digestion media consisted of a modified Hanks' Balanced Salt Solution, pH 7.1, containing 1.6 U/mg wet wt elastase and 8 U/mg wet wt collagenase. This method provided a yield of single smooth muscle cells of approximately 3 x 10(6) cells/100 mg wet wt within 3-4 h of organ removal. Cell viability was determined by trypan blue dye exclusion, retention of lactate dehydrogenase, absence of 57Co-EDTA uptake, and ouabain sensitivity of cationic transport. Roughly 80% of the isolated cells remained viable after the digestion procedure. The dispersed cells specifically bound [3H]PGE2 and [3H]PGF2 alpha. Scatchard analysis of the binding data revealed separate homogenous populations of high affinity sites for both PGE2 and PGF2 alpha. The equilibrium dissociation constants and total sites per cell were 0.55 nM and 11,332 for PGE2 and 0.19 nM and 5,154 for PGF2 alpha, respectively. Specific labeled PG binding was inhibited in a concentration-dependent manner by increasing amounts of unlabeled PG. Inhibition of labeled PGE2 binding by unlabeled PGF2 alpha, and vice versa were negligible, except at high concentrations. The results indicate that smooth muscle cells can be enzymatically dispersed from the rabbit oviduct with minimal damage. Also, these cells possess distinct specific binding sites for PGE2 and PGF2 alpha that differ in regard to affinity and total number of sites per cell.

Animals↗

Poly I:C accelerates ovum transport in the rabbit by a prostaglandin-mediated mechanism.

Administration of poly I:C (1 mg/kg i.v.) to rabbits 24 h after an ovulating injection of hCG caused accelerated ovum transport; only 30% of the ova were still found in the oviducts 24 h later compared with 79% of ova in control animals. This action of poly I:C was prevented by concomitant administration of indomethacin. Poly I:C (0.5 mg/kg i.v.) given to anaesthetized rabbits produced significantly increased levels of prostaglandins (PGs) E and F in uterine vein blood up to 2 h later. Production of PGs by lung, oviduct and myometrium was unaffected 2 h after poly I:C administration, but production of both PGE and PGF by endometrium was significantly elevated at the same time. Metabolism of PGs by cytosols of lung, oviduct and uterus was inhibited to various degrees at 2 h after poly I:C (1 mg/kg i.v.), but by 4 h after treatment this process was reduced to 70--80% of pretreatment values. It is concluded that poly I:C accelerates ovum transport through the oviduct by a PG-mediated mechanism, and that elevated levels of PGs in oviduct are due to inhibition of metabolism of PGs.

Animals↗

Role of prostaglandins in contractile activity of the ampulla of the rabbit oviduct.

Contractile activity of the ampulla of rabbit oviducts removed 24 h after an ovulating injection was studied in vitro. Spontaneous activity, field-stimulated activity, and response to phenylephrine were studied in normal, reversed, and scraped (endosalpinx removed) sections of tissues in the presence or absence of inhibitors of prostaglandin synthetase (8 or 51 micrograms/ml indomethacin or 10 or 100 micrograms/ml 5,8,11,14-eicosatetraynoic acid (ETA)). The effects of in vivo treatment with 10 mg/kg of indomethacin on the same responses were examined. Scraped tissues produced more prostaglandin E and F (measured by radioimmunoassay) than did normal tissues, and this production was suppressed by 10 micrograms/ml of indomethacin or 100 micrograms/ml of ETA. Production of prostaglandin by normal tissues was not depressed by these compounds in vitro, but was significantly reduced by pretreatment of the animals with indomethacin in vivo. In the absence of the endosalpinx, the myosalpinx exhibited spontaneous activity and responded to field stimulation and phenylephrine. Scraped and reversed tissues, however, showed a faster decline in response to field stimulation than normal tissues, and this was due to the traumatization. By contrast, traumatization increased the sensitivity of the tissue to respond to phenylephrine. Inhibition of prostaglandin synthetase by low doses of indomethacin or ETA prevented desensitization of the tissue to field stimulation, but this desensitization was little affected by the higher doses of indomethacin in vitro or in vivo. ETA did not affect the phenylephrine dose-response curves and nor did 8 micrograms/ml of indomethacin, whereas the high dose was inhibitory. Spontaneous activity was only affected by the in vivo pretreatment with indomethacin, which prevented the decline in activity of scraped tissue with time.

Animals↗

Effect of endotoxin treatment on prostaglandin metabolism by rabbit uterus and oviduct.

Metabolism of PGE-2 and PGF-2 alpha by cytosolic fractions (100,000 g supernatant) of the uterus, oviduct and lung of rabbits treated with hCG and endotoxin (20 microgram/kg) was measured. Endotoxin caused immediate decreases in metabolism of both PGs by uterus at 1 h, and these decreases became significant at 2 h for PGE-2 and 6 h for PGF-2 alpha. The metabolism of both PGs remained depressed throughout the 24 h study. Metabolism by oviduct tissue differed in that at 1 h metabolism of both PGs increased but then remained depressed between 2 and 24 h. Metabolism of PGs by lung also showed a different pattern: that of PGE-2 was depressed only briefly (at 2 h), while that of PGF-2 alpha was consistently depressed between 2 and 24 h. Pre-treatment with hCG did not affect the response: tissues from animals killed 6 h after endotoxin but not given hCT responded like those from animals treated with endotoxin 24 h after hCG and killed 6 h later. Much of the increased PG levels in venous drainage after endotoxin treatment can be explained by depressed ability of cells to metabolize PGs.

Animals↗

Influence of hCG injection and steroid treatment on prostaglandin metabolism by rabbit uterus and oviduct.

Metabolism of PGE-2 and PGF-2 alpha by cytosolic fractions (100 000 g supernatant) of rabbit uterus, oviduct and lung was measured in vitro. Metabolism of PGE-2 was greater than that of PGF-2 alpha for oviduct and uterus. After an ovulating injection of hCG metabolism of both PGE-2 and PGF-2 alpha by lung and uterus declined linearly up to 72 h (during the time of ovum transport). The amount of PG metabolism by the oviduct did not change significantly during this period, but the percentage changes of PGE-2 and PGF-2 alpha metabolism from oestrous values did differ, and perhaps indicated a change in the ratio of intracellular PGs. No change of metabolism of either PG by lung, uterus or oviduct occurred at 24 or 72 h after an injection of 250 micrograms oestradiol cyclopentylpropionate given concomitantly with the hCG (a treatment regimen which causes 'tube-locking' of ova). However, progesterone treatment, in a regimen known to cause accelerated transport of ova through the oviduct, caused significantly enhanced metabolism of both PGE-2 and PGF-2 alpha by uterus and oviduct, but not lung, 30 and 48 h later except for PGE-2 by uterus at 30 h. These results suggest that changes in metabolism of PGE-2 and PGF-2 alpha by the oviduct may be involved in the mechanisms controlling ovum transport.

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Contraceptive properties of endotoxin in rabbits.

Endotoxin derived from Salmonella enteritidis-Boivin at a dose of 20 micrograms/kg intravenously interfered with follicular rupture normally induced by human chorionic gonadotropin (hCG) in rabbits. This action was greatest when the endotoxin was given 5 to 6 hours after the administration of hCG. The failure of follicular rupture resulted in entrapment of ova. Endotoxin (5 micrograms/kg) given intravenously to rabbits on day 4 of pregnancy resulted in failure of implantation. Indomethacin (2 micrograms/kg) given intramuscularly concomitantly was unable to reverse this action. Endotoxin (5 micrograms/kg) given intravenously to rabbits on day 8 of pregnancy had an immediate lethal action on embryonic development, and this effect was inhibited by concomitant indomethacin treatment. Nevertheless, most fetuses died after the indomethacin treatment. Whether this was due to a direct toxic action of indomethacin or to a secondary action of endotoxin not blocked by indomethacin is not clear. Endotoxin did not exert its antifertility actions through a luteolytic mechanism.

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Endotoxin-induced acceleration of ovum transport in rabbits.

Salmonella enteritidis-Boivin endotoxin (1--20 microgram/kg) induced accelerated oviductal ovum transport in rabbits in a dose-related manner. Indomethacin prevented this effect. Levels of prostaglandin E and F in uterine vein blood increased following endotoxin injection.

Animals↗

Accelerated ovum transport in rabbits induced by endotoxin II. Changes in oviductal smooth muscle activity.

Oviductal mortility, measured with open-ended perfused catheters in anesthetized animals injected with human Chorionic Gonadotropin (hCG), is depressed 2 h following endotoxin injection and returns to control levels by 3 h after endotoxin injection. This decrease in motility is prevented by indomethacin. Endotoxin did not affect spontaneous or phenylephrine (PE)-induced contractions of oviduct when it was added to the bathing medium of in vitro tissues. Oviductal segments removed 2 h after endotoxin (26 h after hCG) showed electrical activity confined to the ampullary-isthmic-junction (AIJ), where ova were located; the dose-response curve for PE was shifted to the right and the maximum contraction was depressed. Activity of tissues removed 4 h after endotoxin more closely resembled control tissues except that the maximum contraction to PE was depressed, ova had passed out of the oviduct and a proovarian bias in the isthmus was not present. The response of the oviduct to prostaglandins (PGs) in vivo is critically dependent on the previous exposure to PGs. In endotoxin-treated animals PGE then PGF levels increase and the decrease in motility coincides with increased PGE levels, but accelerated ovum transport with the return of motility and activation of the isthmus.

Animals↗

Endotoxin-induced interruption of early pregnancy in the rabbit.

Endotoxin derived from Salmonella enteritidis (Boivin) completely interrupted pregnancy in the rabbit when given as a single dose (10 or 20 microgram/kg) intravenously on Day 4 or Day 8 of pregnancy. Indomethacin (2 or 10 mg/kg) was unable to prevent this effect.

Abortifacient Agents↗

Uterine blood flow and prostaglandin levels in ovariectomized rabbits.

Blood flow (measured by radioactive microspheres) through the uteri of ovariectomized rabbits increased significantly by 2 h, was lower at 4 and 8 h, and returned to control values by 24 h after an injection of 25 microgram oestradiol-17beta. Blood flow through the kidneys was not affected. Concentrations of PGF and PGE in uterine vein blood were elevated after oestrogen treatment. PGF values were significantly greater than control. PGE concentrations, while elevated, were not significantly different from control, although the pattern of release was similar to that of PGF. Pretreatment of animals with progesterone or L11204, or concurrent treatment with indomethacin did not modify the blood flow through the uterus. It is concluded that the increased uterine blood flow seen after oestrogen treatment is not related to prostaglandin production.

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Effect of inhibitors of prostaglandin synthesis and metabolism on ovum transport in the rabbit.

Several drugs known to affect prostaglandin synthesis, release, or metabolism have been tested for their effects on ovum transport in the rabbit after systemic or local administration. Acceleration of transport was obtained with several drugs; among the most effective were benzydamine, a blocker of thromboxane production, and L11204, an inhibitor of prostaglandin metabolism.

Animals↗

Cyclic nucleotides and prostaglandins (PGs) produced by the rabbit oviduct: effects of estrogen treatment.

Levels of cyclic AMP and cyclic GMP have been measured in oviducts of rabbits killed 68 hr after injection of human chorionic gonadotrophin (HCG) to induce ovulation. cAMP and cGMP levels were higher in the isthmus than in the ampulla. Estrogen treatment given at the same time as HCG increased cGMP levels. Levels of PGE and PGF in blood draining the oviduct were low and showed no effect of estrogen treatment at 68 hr after HCG.

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