Action of progesterone on contractile activity of isolated gastric strips in rats.
OBJECTIVE
To study the effect of progesterone on contractile activity of isolated gastric strips in rats.


METHODS
Wistar rats were sacrificed to remove whole stomach. Then, the stomach was opened and the mucosal layer was removed. Parallel to either the circular or the longitudinal fibers, muscle strips were cut from fundus, body, antrum and pylorus. Each muscle strip was suspended in a tissue chamber containing 5 mL Krebs solution. Then the motility of gastric strips in tissue chambers was simultaneously recorded. The preparations were subjected to 1 g load tension and washed with 5 ml Krebs solution every 20 min. After 1 h equilibration, progesterone or antagonists were added in the tissue chamber separately. The antagonists were added 3 min before using progesterone (50 micromol/L(-1)).


RESULTS
Progesterone decreased the resting tension of fundus and body longitudinal muscle (LM) (P<0.05). It inhibited the mean contractile amplitude of body and antrum LM and circular muscle (CM), and the motility index of pyloric CM (P<0.05). The inhibition of progesterone on the mean contractile amplitude could be partially blocked by phentolamine in LM of the stomach body (the mean contractile amplitude of body LM decreased from -7.5+/-5.5 to -5.2+/-4.5 P<0.01), and by phentolamine or indomethacin in CM of body (The inhibition of progesterone on the mean contractile amplitude of body CM decreased from -5.6+/-3.0 to -3.6+/-2.7 by phentolamine and from -5.6+/-3.0 to -3.5+/-2.5 by indomethacin, P<0.01). Hexamethonium, propranolol and L-NNA (inhibitor of NO synthetase) didn't affect the action of progesterone (P>0.05).


CONCLUSIONS
The study suggested that progesterone can inhibit the contractile activity of isolated gastric strips in rats and the mechanism seems to be a direct one except that the action on gastric body is mediated through prostaglandin and adrenergic alpha receptor partly.
Wang
Fang
F
Insititute of Infectious Diseases, the Third Military Medical University Afflicated Southwest Hospital, Chongqing 400038, China. kaixin919@163.com
Zheng
Tian-Zhen
TZ
Li
Wei
W
Qu
Song-Yi
SY
He
Di-Ying
DY
D000818:Animals; D005769:Gastrointestinal Motility / Q000187:drug effects; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology; D010646:Phentolamine / Q000494:pharmacology; D011374:Progesterone / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013270:Stomach / Q000187:drug effects* / Q000502:physiology
D011374:Progesterone; D007213:Indomethacin; D010646:Phentolamine