Phosphodiesterases 1 and 2 regulate cellular cGMP level in rabbit submandibular gland cells.
In rabbit salivary glands, stimulation of muscarinic cholinergic receptors causes production of cGMP through intracellular Ca2+ and nitric oxide. In this study, we investigated a role of cyclic nucleotide phosphodiesterase (PDE) in regulating the cellular cGMP level by using cells dispersed from the submandibular gland. Methacholine, a cholinergic agonist, rapidly elevated the cGMP level. The elevation was greatly enhanced by IBMX, a non-specific inhibitor for most isoforms of the 11 PDEs. The cGMP level was also elevated by MM-IBMX and EHNA, which inhibit the activities of PDE1 and PDE2, respectively. The elevation by the simultaneous application of the two drugs corresponded to 90% of that by IBMX. Therefore, PDE1 and PDE2 are the main PDEs that act to degrade cGMP in methacholine-stimulated cells. The presence of the two PDEs was confirmed by assaying their activities of the cell lysate. In unstimulated cells, the cGMP level was elevated by MM-IBMX and little elevated by EHNA. While the PDE2 activity was thus low, it was estimated that methacholine increases its activity approximately 50-fold. The strong activation can be explained by the elevation of the cGMP level because PDE2 is a cGMP-stimulated PDE. SNAP, a nitric oxide donor, causes production of cGMP without a receptor-operated increase in intracellular Ca2+ concentration. In SNAP-stimulated cells, MM-IBMX elevated the cGMP level higher than in methacholine-stimulated cells although the PDE1 activity is dependent on Ca2+/calmodulin. Besides Ca2+, other factors may regulate the PDE1 activity in living cells.
Michikawa
Hiromi
H
Department of Physiology, Nihon University School of Dentistry at Matsudo, 2-870-1 Sakaecho-nishi, Matsudo, Chiba 271-8587, Japan. mitikawa@mascat.nihon-u.ac.jp
Sugiya
Hiroshi
H
Yoshigaki
Tomoyoshi
T
Fujita-Yoshigaki
Junko
J
Furuyama
Shunsuke
S
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism*; D006868:Hydrolysis; D007527:Isoenzymes / Q000378:metabolism*; D016210:Methacholine Chloride / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D011817:Rabbits; D013363:Submandibular Gland / Q000166:cytology / Q000378:metabolism*
D007527:Isoenzymes; D016210:Methacholine Chloride; D010727:Phosphoric Diester Hydrolases; D006152:Cyclic GMP; D015056:1-Methyl-3-isobutylxanthine