Determination of the effect of nitric oxide on small intestinal motility in 17ß-estradiol applied ovariectomized rats

In this study, it was investigated the effects of different doses of 17ß-estradiol on small intestinal contractility in 3-6 months old, 24 Sprague Dawley ovariectomized rats, weighting 270±20 gr. Animals were apportioned into one control (Ov) and three experimental groups (estrogen) (n=6 each). The control group received 0,2 sesame oil once daily for three days, whereas rats in the first, second and third experimental groups were treated with intra muscular 25, 50 and 100 ?g 17ß-estradiol, respectively.The rats were killed under general anesthesia, 18 hours after the termination of last treatment. Then, small intestinum of the animals were cut into duodenum, jejenum and ileum. Organ bath was used to evaluate isometric smooth muscle contractility. In order to determine endogenous and exogenous nitric oxide activity and to evaluate the efficiency of cyclic guanosine monophosphate (cGMP), L-Arginine, sodium nitro prusside (SNP) and 8-Br-cGMP were used, respectively.It was determined that estrogen decreased the tension of spontaneous contractility of duodenum and ileum but not in jejenum. However, L-arginine, SNP and 8-Br-cGMP were decreased the tension of spontaneous contractility of small intestinum. On the other hand, it was observed that estrogen decreased the relaxing activity of L-Arginine and 8-Br-cGMP, dose dependently but increased the activity of SNP.In conclusion, it was determined that 17ß-estradiol decreased the tension of spontaneous contractility in duodenum and ileum, dose dependently and nitric oxide and cGMP did not mediate this activity.Key Words: 17ß-estrodiol, small intestine, cGMP, Nitric oxide, Rat