The presence of five cyclic nucleotide phosphodiesterase isoenzyme activities in bovine tracheal smooth muscle and the functional effects of selective inhibitors

Abstract

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-hydioxy-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 Ca2+/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 ,umol 1-1), indicating the presence of PDE III activity. 2) did not completely relax preparations at concentrations up to 100 pImol I-. Org 30029 (pD2 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.

Effects of Various Selective Phosphodiesterase Inhibitors on Carbachol-Induced Contraction and Cyclic Nucleotide Contents in the Guinea Pig Gall Bladder

“…It is well known that PDE4 is specific for the hydrolysis of cAMP [3]. It has been reported that rolipram (type 4 inhibitor) relaxed bovine trachea by an increase in the cAMP content [19]. In the present study, there was a positive correlation between the inhibition of CCh-induced contractions and the increase in cAMP content elicited by Ro20-1724 in the gall bladder.…”

Cyclic nucleotide phosphodiesterases in pancreatic islets

“…Pharmacological characterization of PDE3 has been greatly facilitated by the development of potent, highly selective inhibitors of this isoform, such as SK&F 94836 (siguazodan) [60] and Org 9935 [61]. We found that SK&F 94836 and Org 9935 were very potent inhibitors of rat islet PDE activity, especially in membrane fractions [57] with up to 85% of membrane-bound PDE being inhibited with IC 50 values of 5.5 and 0.05 µmol/l respectively.…”

Inhibitory Mechanism of Papaverine on Carbachol-Induced Contraction in Bovine Trachea

“…However, in aorta, milrinone, a PDE3 inhibitor, inhibited norepinephrine-induced contraction more potently than Ro20-1724, a PDE4 inhibitor (36). On the other hand, rolipram, a PDE4 inhibitor, inhibited methacholine-or histamine-induced contraction more potently than milrinone in bovine trachea (37). In addition, AH 21-132, a papaverine derivative compounds, inhibited PDE4 (cAMP-specific PDE) more selectively than other PDEs in bovine tracheal smooth muscle (38).…”