An investigation was undertaken to study the effect of Chronic hyperprolactinemia induced by pituitary homograft underneath the kidney capsule on the induction of gastric ulceration in standard model using cold-plus-restraint stress. Male Wistar strain rats weighing 240 土20g were divided into two groups: one received two pieces of anterior pituitary gland from its littermates, the other grafted with several pieces of muscle served as control. Rats were housed in a temperature-controlled room (24土2°C) with a regular lighting schedule ( 14hrs on; 10 hrs off ). Laboratory chow and tap water were available at all times.
Experiment 1 For both pituitary-grafted group and control group, blood samples were withdrawn from jugular vein before transplantation and at an interval of 5~10 days
after transplantation under light ether anesthesia. Serum prolactin was measured by radioimmunoassay. From the 5th day to the 40th day after transplantation, the level of serum prolactin in the pituitary-grafted group was higher than those of control ( p < 0.05 or p < 0.01 )
Experiment 2: Rats were also divided into two groups as above, except that no blood samples were collected during the period of 40 days after grafts transplantation. On the fortieth day after transplantation, all rats in this experiment 2 were fastened overnight. All rats were restrainted and placed supine in a ventilated refrigerator with an ambient temperature of 5°C for 3 hrs. Gastric ulceration was induced. These results showed that the number of ulcers was lower in pituitary grafted group (12.5 士1. 2) than that in control group (23.0 土2.9) (p< 0.05) ,and the total ulcer length (mm) was lower in pituitary grafted group (3.03 土0 .4 mm) than that in control group (5.98 士1. 0 mm) (p< 0.01).
Experiment 3: On the fortieth day after transplantation, the pylorus of rats had been ligated for 6 hours with modified Shay's method, in order to analyze various data concerning their gastric juice. According to our finding, the data of gastric
secretion, free HCl and total acidity of gastric juice were not significantly different in both groups. According to these findings, we could say that hyperprolactinemia induced by grafting two pieces of anterior pituitary glands beneath the kidney capsule might be related to the reduction of gastric ulceration, but the attenuated degree of ulceration was not directly related to the inhibitory action of gastric acid secretion. Hyperprolactinemia related to the protection of gastric mucosal was also discussed in this study. More detailed mechanism for such relation remains to be clarified.
