Jussi Männistö

Indomethacin inhibits arachidonic acid metabolism via lipoxygenase and cyclo-oxygenase in hamster isolated lungs.

14C-Arachidonic acid (AA, 66 nmol) was injected into the pulmonary circulation of isolated perfused hamster lungs. The metabolites were analysed from the nonrecirculating perfusion effluent, which was extracted with ethyl acetate first at pH 7.4 (to extract unmetabolized AA, metabolites of lipoxygenase and HHT) and then at pH 3.5 for prostaglandins and thromboxanes. When indomethacin was infused into the pulmonary circulation, the metabolism of AA was decreased dose dependently. The amounts of all metabolites were decreased rather similarly by indomethacin. The present study indicates that indomethacin inhibits arachidonate metabolism via cyclo-oxygenase and lipoxygenase in hamster isolated lungs.

The effect of cigarette smoke on the metabolism of arachidonic acid in isolated hamster lungs

The effects of cigarette smoke on the metabolism of exogenous arachidonic acid (AA) were investigated in isolated hamster lungs. Arachidonate was injected into the pulmonary circulation and the metabolites were analysed from the nonrecirculating perfusion effluent by thin layer chromatography. After the pulmonary injection of 66 nmol of 14C-AA about 20% of the injected radioactivity appeared in the perfusion effluent mostly as metabolites in six minutes. When isolated lungs were ventilated with cigarette smoke during the perfusion, the amounts of PGF2 alpha, PGE2 and two unidentified metabolite groups increased in the lung effluent. In two other experimental series hamsters were exposed to cigarette smoke before the lung perfusion either once for 30 min or during one hour daily for ten consecutive days. Neither pre-exposures caused any changes in the amounts of arachidonate metabolites in the lung effluent.

The metabolism of arachidonic acid in isolated hamster, rat and guinea pig lungs

The perfusion effluent from isolated rat lungs caused relaxations of superfused strips of bovine (BBBCA) and pig (PCA) coronary arteries. The effluent from hamster lungs had similar effect on BCA. Bolus injections of arachidonate (AA, 10-20 microgram) into rat lungs caused further relaxations of superfused BCA and contractions of rat stomach strip (RSS). AA injections into guinea pig lungs resulted in dose dependent contractions of BCA and PCA. Similar dose dependent contractions of PCA and RSS were seen in hamster experiments, however the responses of BCA varied with the AA dose. Infusion of AA (5-25 microgram/min) into guinea pig lungs resulted in dose dependent contractions of superfused PCA and BCA. In hamster experiments AA infusion (5 microgram/min) caused a small relaxation of BCA, but had no effect on PCA. When 14C-AA was injected into the pulmonary circulation, the amounts of metabolites were greater in the perfusion effluent from hamster than from rat lungs. In rat lungs 6-oxo-PGF1 alpha was one of the main metabolites. In contrast, in hamster lungs this metabolite represented only a small part of the total metabolite formation. Thromboxane B2 was one of the main metabolites formed in hamster lungs and its rate of formation increased greatly with increasing AA doses. The results indicate that the metabolite pattern of arachidonate in isolated rat lungs is different from that in hamster and guinea pig lungs. The total rate of AA metabolism in rat lungs is smaller than in hamster lungs.

Cigarette smoke ventilation decreases prostaglandin inactivation in rat and hamster lungs

The effects of cigarette smoke on the metabolism of exogenous PGE2 and PGF2 alpha were investigated in isolated rat and hamster lungs. When isolated lungs from animals were ventilated with cigarette smoke during pulmonary infusion of 100 nmol of PGE2 or PGF2 alpha, the amounts of the 15-keto-metabolites in the perfusion effluent were decreased. Pre-exposure of animals to cigarette smoke daily for 3 weeks did not change the metabolism of PGE2 when the lungs were ventilated with air. Cigarette smoke ventilation of lungs from pre-exposed animals caused, however, a similar decrease in the metabolism of PGE2 as in animals not previously exposed to smoke. After pulmonary injection of 10 nmol of 14C-PGE2 the radioactivity appeared more rapidly in the effluent during cigarette smoke ventilation suggesting inhibition of the PGE2 uptake mechanism. In rat lungs pulmonary vascular pressor responses to PGE2 and PGF2 alpha were inhibited by smoke ventilation.

The metabolism of arachidonic acid is changed by dipyridamole in isolated hamster lungs

14C-Arachidonate (50 nmol) was injected into the pulmonary circulation of isolated perfused lungs of female hamsters and the metabolites were analysed from the nonrecirculating perfusion effluent. Pulmonary infusion of dipyridamole (20 microM) increased the amount of radioactivity in the perfusion effluent of 0-4 min from 12.8 +/- 1.0% to 17.2 +/- 1.5% (2P less than 0.05) of the injected amount. Dipyridamole increased the amounts of PGF2 alpha, PGE2 and two unidentified metabolite groups in the effluent. An increasing trend was seen also in the amount of 6-keto-PGF1 alpha and TxB2. A decreasing trend was, however, seen in the amount of metabolites migrating near to unlabelled 15-keto-PGE2. When 20 nmol of 14C-PGE2 was injected into the pulmonary circulation of isolated hamster lungs, the amount of 15-keto-metabolites of PGE2 in the effluent was decreased and that of unmetabolized PGE2 increased by dipyridamole dose dependently. The rate of efflux of radioactivity from the lungs was increased by dipyridamole. Dipyridamole was in vitro not an inhibitor of 15-hydroxyprostaglandin dehydrogenase in the 100.000 supernatant fraction of homogenized hamster lungs. At 20 microM and 100 microM it even caused a slight in vitro activation of 15-hydroxyprostaglandin dehydrogenase. Thus the decreased pulmonary inactivation of PGE2 by dipyridamole is obviously due to the decreased uptake of PGE2 into the lungs. This could explain partly the detected changes in the pulmonary metabolism of arachidonic acid by dipyridamole.

The inactivation of prostaglandin E2 is decreased by dipyridamole and sulfinpyrazone in isolated rat lungs

The inactivation of prostaglandin E2 (PGE2) was decreased in the pulmonary circulation of isolated rat lungs, when either dipyridamole or sulfinpyrazone was infused into the pulmonary artery at the concentration of 20 microM. After pulmonary injection of 7.1 nmoles of 14C-PGE2 the amount of 15-oxo-metabolites of PGE2 in the effluent was 3.91 +/- 0.19 nmoles from control lungs and 2.05 +/- 0.19 nmoles (2P less than 0.001) in that from 20 microM dipyridamole treated lungs. The corresponding values for control and 20 microM sulfinpyrazone lungs were 4.11 +/- 0.25 and 3.03 +/- 0.14 nmoles (2P less than 0.01), respectively. The amounts of unmetabolized PGE2 were correspondingly increased in the effluents from dipyridamole and sulfinpyrazone (20 microM) lungs. Neither dipyridamole nor sulfinpyrazone had at concentration of 2 microM any significant effect on the amount of 15-oxo-metabolites in the effluent, although the amount of unmetabolized PGE2 was slightly increased in 2 microM sulfinpyrazone experiments.

The effect of cigarette smoke on the metabolism of arachidonic acid to myotropic compounds in rat and hamster isolated lungs

Perfusion effluent from isolated rat and hamster lungs caused a relaxation of superfused strip of bovine coronary artery (BCA). This relaxation was abolished by pulmonary infusion of indomethacin. Pre-exposure of rats and hamsters to cigarette smoke during half an hour before the lung perfusion did not change the degree of this initial relaxation of BCA. Injection of 10 micrograms of sodium arachidonate (AA) into the pulmonary circulation of isolated hamster lungs caused a contraction of BCA, which was not changed by cigarette smoke pre-exposure. When AA (10 micrograms) was injected into the pulmonary circulation of isolated hamster lungs during cigarette smoke ventilation the contractions of superfused BCA and rat stomach strip (RSS) were not significantly different from those during the preceding and following air ventilation. In experiments with isolated rat lungs the initial relaxation of superfused BCA was accompanied by a contraction of superfused RSS. AA injection (10 micrograms) into rat lungs caused a further relaxation of BCA and contraction of RSS, which were abolished by pulmonary infusion of indomethacin. Cigarette smoke ventilation of isolated rat lungs caused a relaxation of superfused BCA, which was not abolished by indomethacin. During cigarette smoke ventilation injection of AA (10 micrograms) into the pulmonary circulation of rat lungs caused a relaxation of BCA and a contraction of RSS. The present study indicates that neither cigarette smoke ventilation nor pre-exposure to cigarette smoke has a drastic effect on the metabolism of arachidonic acid to myotropic compounds in isolated hamster and rat lungs.

Metabolism of testosterone and progesterone by gastrointestinal tissues of the pike (Esox lucius)

[4-14C]Testosterone and [4-14C]progesterone were incubated with homogenates of liver and of esophageal, gastric, and intestinal mucosa of the pike (Esox lucius). The esophageal and gastric incubations produced both 5α- and 5β-reduced metabolites, but only 5β-reductase was found in the intestinal and hepatic incubations. The metabolism in the intestinal and hepatic samples was almost identical both qualitatively and quantitatively and more active than that in the esophageal and gastric samples. The pattern of pike intestinal metabolism differs from that observed in a number of mammalian species.

The effects of cigarette smoke on the fate of arachidonic acid in rat and hamster lungs

The effects of cigarette smoke on the fate of exogenous arachidonic acid (AA) were investigated in isolated perfused rat and hamster lungs. 14C-arachidonate was infused into the pulmonary circulation and the metabolites in the effluent as well as the distribution of radiolabel in lung lipids were analysed. Pre-exposure of animals to cigarette smoke daily for three weeks did not change the amounts of metabolites in lung effluent or the incorporation of AA into lung lipids. Cigarette smoke ventilation of lungs from pre-exposed hamsters changed the amounts of some metabolites of AA in the effluent. The distribution of radioactivity in the lung tissue was changed during smoke ventilation in both rat and hamster. The amount of radioactivity in some lipid fractions was increased by cigarette smoke, the increase being greatest in triacylglycerols. This study shows that pulmonary metabolism of AA is changed by cigarette smoke ventilation but not by pre-exposure of animals. Both incorporation of AA into lung lipids and efflux of metabolites from the lungs are affected by cigarette smoke.

Cigarette smoke ventilation decreases thromboxane B2 metabolism in isolated rat lungs

3H-TxB2 was infused into the pulmonary circulation of isolated perfused rat lungs. The metabolites were analysed from the nonrecirculating perfusion effluent. When the lungs were ventilated with cigarette smoke the amount of unmetabolized TxB2 in the effluent was increased by 50%. The amount of the main metabolite was, however, not changed. The efflux of radioactivity from the lungs after a bolus injection of 3H-TxB2 was slower during cigarette smoke ventilation than during air ventilation. This suggests that cigarette smoke inhibits the enzymes metabolizing TxB2 rather than the pulmonary thromboxane uptake system.