Nitric oxide inhibits contraction of isolated pig ureteral smooth muscle.
OBJECTIVE
To investigate the L-arginine/nitric oxide (NO) pathway in the pig isolated ureter.


METHODS
Functional inhibitory effects mediated by NO were assessed and correlated with cyclic nucleotide levels. Nitric oxide synthase (NOS) activity was measured by monitoring the conversion of [3H]-arginine to [3H]-citrulline. Immunohistochemical studies were performed.


RESULTS
The NO-donor SIN-1 reduced in a concentration-dependent manner the frequency of contractions, whereas NO completely interrupted the contractile activity. In precontracted strips exposed to SIN-1 or NO, there were 6- and 12-fold increases of the cyclic GMP levels in comparison with control preparations. Activity of NOS was moderate. Overall innervation of the ureter was sparse, and there were few NOS-immunoreactive nerves.


CONCLUSIONS
Although few NOS-containing nerves were found, pathways regulating the cyclic GMP levels of pig ureteral smooth muscle were demonstrated. Such pathways may be important targets for drugs producing relaxation of the mammalian ureter.
Iselin
C E
CE
Department of Surgery, Geneva University Hospital, Switzerland.
Alm
P
P
Schaad
N C
NC
Larsson
B
B
Graber
P
P
Andersson
K E
KE
D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000187:drug effects*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology; D013552:Swine; D014513:Ureter / Q000033:anatomy & histology / Q000187:drug effects* / Q000502:physiology
D017366:Serotonin Receptor Agonists; D009569:Nitric Oxide; D012701:Serotonin; D006152:Cyclic GMP