Release of prostaglandins

Monoclonal antibodies against E- and F-type prostaglandins. High specificity and sensitivity in conventional radioimmunoassays

Polyclonal antisera against prostaglandins (PGs) are widely used for the assessment of the biological role of these mediators, but even the most specific contain antibodies against the major metabolites and degradation products of the haptens employed. To overcome this inherent problem we produced monoclonal antibodies (mAs) against PGE2, PGF2 alpha and 6-keto-PGF1 alpha using the somatic cell hybridization technique. The mAs against 6-keto-PGF1 alpha and PGF2 alpha proved to be highly specific, but allowed only for moderate detection limits (1-2 ng) in conventional fluid phase radioimmunoassays (RIAs). One of the mAs against PGE2 permitted a 100-fold improvement in the detection limit while being almost devoid of cross-reactivity with metabolites and other structurally related PGs. These results show that highly specific mAs against PGs can be produced to improve the available RIA technique for PG quantification.

Differential effects of prostaglandins on canine intrapulmonary arteries and veins

1 The sensitivity and contractility of isolated canine intrapulmonary arteries and veins to a variety of primary prostaglandin compounds was studied.2 Intrapulmonary arteries produced no measurable contractile responses to prostaglandin A(1) (PGA(1)), PGA(2), PGB(1), PGD(2), PGE(1), PGE(2) or to PGF(1alpha). However, high concentrations of both PGB(2) (> 10(-7) M) and PGF(2alpha) (> 10(-6) M) elicited concentrated-related, but weak, contractile responses, measuring only 5-25% of KCl-induced maximum contractions.3 Intrapulmonary arteries, partially contracted by 5-hydroxytryptamine (5-HT), exhibited concentration-related relaxations in response to PGE(1); PGE(2), PGA(1) or PGA(2) produced only weak superimposed contractions.4 In contrast to intrapulmonary arteries, intrapulmonary veins contracted in a concentration-related fashion to all prostaglandins tested, where the contractile sensitivity was (based on EC(50) s and threshold concentrations): PGB(2) > PGB(1) > PGD(2) > PGF(2alpha) > PGA(2) >> PGA(1) > PGF(1alpha) > PGE(2) > PGE(1).5 In terms of the ability to generate maximum contractile responses on intrapulmonary veins, the prostaglandins were also variable, with PGA(2) and PGB(2) being the most potent and PGD(2) the least potent.6 Intrapulmonary veins, partially contracted by 5-HT, exhibited concentration-related relaxations to PGE(1) at low concentrations, followed by secondary contractile responses at higher concentrations.7 Neither PGA(1) nor PGA(2) (3.4 x 10(-8) to 3.4 x 10(-5) M) inhibited or potentiated 5-HT responses of intrapulmonary arteries.8 These data suggest that there are species, regional and major qualitative and quantitative, differences in the responsiveness of intrapulmonary arteries and veins to prostaglandin.

Intravesical prostaglandin: release and effect of bladder instillation on some micturition parameters

Bladder washout effluent fluid was examined for prostaglandin-like activity following acidic lipid extraction and bioassay using the rat-stomach strips technique. A low basal level of prostaglandin-like material was detected in washouts collected when the bladder was empty in 4 out of 7 dogs. Increased levels were detected following micturition in 5 of these 7 dogs. A significantly high level of prostaglandin-like material was recovered after pelvic nerve stimulation. The prostaglandin-like material was tentatively identified as PGE based on the bioassay with the addition of specific antibody. Intravesically administered PGE2 or PFG2 alpha significantly reduced, in a dose-dependent response, the threshold micturition volume. All of these findings suggested that prostaglandins may play a role in the micturition process.

Reactivity of isolated rat and canine pulmonary arteries to prostaglandins

In this investigation, the sensitivity and contractility of isolated rat and canine pulmonary arteries to a variety of prostaglandin compounds (PGs) were studied. Based on EC50's and threshold concentrations, the contractile sensitivity of rat pulmonary arteries to PGs was: PGB2 > PGA2 > PGF2 alpha approximately equal to PGE2 > PGB1 approximately equal to PGA1 > PGF1 alpha approximately equal to PGE1 > PGD2. In terms of the ability to generate a maximum contractile responses on rat pulmonary arteries, the PGs were also variable, where PGB2 was the most potent and PGD2 the least potent agonist. None of these contractile responses were tachyphylactic on rat pulmonary arteries. Surprisingly, except for PGB2, none of the PGs elicited reproducible contractile responses on canine pulmonary arteries. The present data, therefore, clearly indicate that there are species differences with respect to the contractile action of PGs on pulmonary vessels. In addition, these findings suggest that a clear structure-activity relationship exists for the contractile action of PGs on rat pulmonary arteries. The latter differential reactivity may be important in hypoxic pulmonary vasoconstriction and allergic hypersensitivity phenomena in certain mammals.

Effect of sparteine sulfate on uterine prostaglandin F in the rat

Indomethacin, an inhibitor of prostaglandin synthetase, added to an in vitro bath in a concentration of 1, 5, and 10 X 10(-6) g/ml reduced sparteine-induced contractions of isolated uterine segments from pregnant rats. Contractions induced by prostaglandin F2alpha and acetylcholine were not reduced. Sparteine increased the prostaglandin F content of the blood and uterine tissue in the pregnant but not in the nonpregnant rat. This increase was significantly reduced by the administration of indomethacin (10 mg/kg). The present study suggests that the mechanism of sparteine action is mediated through a prostaglandin F system.

Considerations into the mechanism of estrogen-stimulated uterine prostaglandin synthesis

Progesterone priming of the ovariectomized rat, followed by a single injection of estradiol-17beta (10 mug) is followed by an increased uterine synthesis of both PGF and PGE. The administration of an estrogen antagonist (MER-25; 10 mg) concomitantly with estradiol had no effect on uterine prostaglandin synthesis. Similarly, the administration of either Actinomycin D or cycloheximide, antibiotics demonstrated to inhibit mRNA and protein synthesis, respectively, is without effect on estrogen-stimulated uterine prostaglandin synthesis. These results are considered with regard to the classic receptor theory of estrogen action and are a preliminary indication that estrogen-stimulated uterine prostaglandin synthesis may not require those receptor mediated events.

Prostaglandins and cholera: the occurrence of prostagland in-like smooth muscle contracting substances in cholera diarrhoea

Prostaglandin-like smooth muscle contracting substances were identified in acid lipid extracts of diarrhoeal faeces taken from patients presenting clinical symptoms of cholera. Five out of the eleven cases studied were bacteriologically confirmed as cholera. The PG-like activity in the individual samples ranged from 3-27 mg PGE2 equivalents /ml of diarrhoeal stool. Parallel bioassay and thin-layer chromatographic analysis of the extracts indicated that about 60% of the activity was due to an F-type PG, 15% to an E-type PG and the rest to unidentified lipid substanc(s). It is proposed that increased PG production in cholera (indicated by these findings) may at least contribute to the disease.