S. Rattan et S. Chakder, Influence of heme oxygenase inhibitors on the basal tissue enzymatic activity and smooth muscle relaxation of internal anal sphincter, J PHARM EXP, 294(3), 2000, pp. 1009-1016
Citations number
52
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
We examined the actions of different heme oxygenase (HO) inhibitors on the
basal HO activity in the opossum internal anal sphincter (IAS), rectum, and
liver tissues and the IAS smooth muscle relaxation in response to nonadren
ergic noncholinergic (NANC) nerve stimulation and different agonists. All t
he tissues examined were found to have significant levels of basal HO activ
ity, Among different HO inhibitors, tin protoporphyrin IX (SnPP IX) was fou
nd to be most selective in inhibiting the HO activity in the IAS smooth mus
cle. Conversely, in the liver, all the HO inhibitors except SnPP IX caused
significant inhibition of HO activity. Consistent with HO activity inhibiti
on, the IAS smooth muscle relaxations caused by NANC nerve stimulation and
vasoactive intestinal polypeptide also were inhibited by zinc protoporphyri
n IX and SnPP IX. Zinc protoporphyrin IX also caused a significant attenuat
ion of the IAS smooth muscle relaxation caused by isoproterenol. The IAS sm
ooth muscle relaxation caused by nitric oxide was not significantly modifie
d by any of the HO inhibitors. The data show the presence of HO activity in
the IAS and other gastrointestinal tissues. The differential attenuation o
f HO activity by different HO inhibitors in the IAS smooth muscle and liver
confirms the presence of different isozymes of HO in different tissues. Su
ppression of basal HO activity and the IAS smooth muscle relaxation induced
by NANC nerve stimulation or VIP but not NO suggest that some of the stimu
li that cause IAS smooth muscle relaxation may involve HO activity.