Collagen solubility and tensile properties of the rat uterine cervix in late pregnancy: effects of arachidonic acid and prostaglandin F 2 alpha

The collagen concentration in rat uterine cervix was less on day 18 of pregnancy than in the non-pregnant animal but did not diminish further as pregnancy proceeded. The solubility of cervical collagen in warm acetic acid (0.5 mol/l) was increased on day 22 compared with days 19, 20 and 21 of pregnancy, and there was a positive correlation of increasing solubility with the tissue rate of creep (a measure of reducing stiffness of the cervix). Treatment of rats subcutaneously with arachidonic acid or prostaglandin F 2 alpha (PGF 2 alpha) on day 18 of pregnancy decreased the stiffness of the tissue when assessed on day 19 and this was accompanied by increased solubility in cold saline (0.45 mol/1), cold acetic acid and warm acetic acid and a reduction in collagen concentration. These results suggest that collagen properties rather than concentration are important in determining the stiffness of the rat uterine cervix at term and that exogenous PGF 2 alpha and arachidonic acid cause biochemical changes in collagen structure unlike those seen at term in untreated animals.

The effect of arachidonic acid and prostanoids on collagen dissolution in human uterine cervix in vitro

Explants of human non-pregnant cervix produce collagenolytic enzymes which degrade collagen over a 10 day period in culture. This is significantly enhanced by the presence of very low concentrations of arachidonic acid (10(-16) - 10(-11)M). Prostaglandin E2, F2 alpha and 6-keto-F1 alpha were synthesised in declining amounts over the 10 day period and synthesis was not increased by adding arachidonic acid (10(-11)M). Meclofenamic acid (10(-6)M) and indomethacin (10(-5)M), but not tranylcypromine (10(-5)M) suppressed prostaglandin synthesis yet all reduced collagen dissolution. Mepacrine (phospholipase A2 inhibitor) also suppressed collagen dissolution. Remodelling of the structure of the cervix matrix may, in part, depend upon arachidonic acid or one of its cyclo-oxygenase or lipoxygenase derived products.

Ulcerative colitis: effect of sulphasalazine, its metabolites and indomethacin on the ability of human colonic mucosa to metabolize prostaglandins in vitro

1 Homogenates of mucosa from human colon metabolize [3H]-prostaglandin E1 in the presence of nicotinamide adenine dinucleotide to 15-oxo prostaglandin E1 or 15-oxo, 13,14 dihydro prostaglandin E1. 2 Metabolic capacity of tissue from patients with active ulcerative colitis under treatment with sulphasalazine (0.021 +/- 0.004 nmol/Mg protein +/- s.e. mean) did not differ from mucosa of normal patients (0.02 +/- 0.004 nmol/mg protein) during 1 h incubation. 3 Sulphasalazine inhibits prostaglandin E1 metabolism by mucosal homogenates in a dose-dependent manner with an ID50 of 125 microM. Its therapeutically active metabolite, 5-aminosalicylic acid (2.6 mM) was without significant inhibitory activity. 4 Indomethacin inhibits prostaglandin E1 metabolism by colonic mucosa with an ID50 of 388 microM. 5 At present we cannot clearly relate the therapeutic benefit of sulphasalazine and its therapeutically active metabolite, 5-aminosalicylic acid, in ulcerative colitis to their effects on prostaglandin E synthesis or metabolism in vitro.

Stimulation of prostaglandin synthesis in rat cerebral cortex via a beta-adrenoceptor

1. Synthesis of prostaglandin E2 (PGE2) and prostaglandin F2 alpha (PGF2 alpha) in rat cerebral cortex slices is increased by beta-adrenoceptor agonists. 2. Phenylephrine, an alpha-adrenoceptor agonist, has no effect while oxymetazoline increased PGF2 alpha only. 3. PG synthesis stimulation by noradrenaline (NA) was prevented by beta- but not by alpha-adrenoceptor antagonists. 4. Dibutyryl cyclic AMP and inhibitors of cyclic nucleotide phosphodiesterase augment PG synthesis. 5. Stimulation of PG synthesis in rat cerebral cortex by NA is mediated by a beta-adrenoceptor.

Regulation of collagen dissolution in the human cervix by oestradiol-17 beta and progesterone

Explants of non-pregnant human cervix in culture for 10 days spontaneously synthesized collagenolytic enzymes with dissolved the collagen in the tissue, resulting in the release of hydroxyproline-containing peptides. Progesterone at 8 X 10(-7) M and oestradiol-17 beta at 4 X 10(-6) M reduced this breakdown by 50%, but oestradiol-17 beta was only inhibitory if the tissue was maintained in an oestrogen-containing environment throughout the preparation of the tissue explants. We conclude that the connective tissue matrix of the human cervix is partly under hormonal control.

Prostaglandin E and F concentrations in placentae of normal, hypertensive and pre-eclamptic patients

The prostaglandins E and F were measured by radioimmunoassay in placentae from 23 normotensive, 25 hypertensive and 13 pre-eclamptic patients. The prostaglandin E levels were respectively (pg/mg +/- SEM) 16.34 +/- 2.06, 16.75 +/- 2.52 and 12.10 +/- 3.63. The prostaglandin F levels were 2.43 +/- 0.41, 2.70 +/- 0.42 and 2.06 +/- 0.31. These prostaglandin concentrations did not differ significantly. Local ischaemia may, therefore, be explained by altered responsiveness to these prostaglandins or to changes in other prostaglandins (such as the vasodilator PGI2) or other vasoactive agents.