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The presence of five cyclic nucleotide phosphodiesterase isoenzyme activities in bovine tracheal smooth muscle and the functional effects of selective inhibitors
Author(s) -
Shahid Mohammed,
Amsterdam Ronald G.M.,
Boer Jacob,
Berge Ronald E.,
Nicholson C David,
Zaagsma Johan
Publication year - 1991
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1991.tb12453.x
Subject(s) - rolipram , ibmx , zaprinast , milrinone , chemistry , phosphodiesterase , cyclic nucleotide phosphodiesterase , cyclic nucleotide , biochemistry , nucleotide , enzyme , endocrinology , biology , forskolin , receptor , gene , inotrope
1 The profile of cyclic nucleotide phosphodiesterase (PDE) isoenzymes and the relaxant effects of isoenzyme selective inhibitors were examined in bovine tracheal smooth muscle. The compounds examined were the non‐selective inhibitor 3‐isobutyl‐1‐methylxanthine (IBMX), zaprinast (PDE V selective), milrinone and Org 9935 (4,5‐dihydro‐6‐(5,6‐dimethoxy‐benzo[b]thien‐2‐yl)‐5‐methyl‐1(2H)‐pyridazinone; both PDE III selective), rolipram (PDE IV selective) and Org 30029 (N‐hydroxy‐5,6‐dimethoxy‐benzo[b]‐thiophene‐2‐carboximidamide HCl a dual PDE III/IV inhibitor). 2 Ion exchange chromatography showed three main peaks of PDE activity. The first peak was stimulated by Ca 2+ /calmodulin (PDE I), the adenosine 3′:5′‐cyclic monophosphate (cyclic AMP) hydrolytic activity of the second peak was stimulated by guanosine 3′:5′‐cyclic monophosphate (cyclic GMP) (PDE II) whilst that of the third peak was not significantly modified by any regulator (PDE IV). Calmodulin affinity chromatography revealed the additional presence of cyclic GMP‐specific PDE (PDE V) in the first peak. A clearly distinct peak of cyclic GMP‐inhibited PDE (PDE III) was not observed. However, Org 9935 inhibited the third activity peak more effectively in the presence, than in the absence, of rolipram (3 μmol l −1 ), indicating the presence of PDE III activity. 3 Rolipram was the most potent inhibitor of PDE IV. The mean −log 50 IC 50 values for rolipram, IBMX, milrinone, Org 30029, Org 9935 and zaprinast were 5.9 ± 0.1, 4.9 ± 0.1, 4.7 ± 0.1, 4.6 ± 0.1 and 4.6 ± 0.1, respectively. 4 Rolipram was a potent relaxant of both histamine (1 μmol1 −1 ) and methacholine (0.03 μmol1 −1 ) precontracted preparations; (pD 2 values; histamine 7.1 ± 0.1, methacholine 6.8 ± 0.2 and 4.5 ± 0.1, biphasic relaxation). IBMX also relaxed all preparations (pD 2 values; histamine 5.6 ± 0.1, methacholine 5.6 ± 0.1) whilst zaprinast (pD 2 values; histamine 5.2 ± 0.1, methacholine 4.4 ± 0.3), milrinone (pD 2 values; histamine 5.2 ± 0.1, methacholine 4.3 ± 0.3) and Org 9935 (pD 2 values; histamine 4.1 ± 0.1, methacholine 4.1 ± 0.2) did not completely relax preparations at concentrations up to 100 μmol1 −1 . Org 30029 (pD 2 values; histamine 6.2 ± 0.1, methacholine 5.4 ± 0.1) was a more effective relaxant than can be explained on the basis of PDE IV inhibition alone. 5 We conclude that bovine tracheal smooth muscle contains five distinct PDE isoenzymes. PDE IV appears to be more important in the modulation of tissue function than PDE III and PDE V.