Subcutaneously administered prolactin and 20K hGH, but not rGH or 22K hGH, prevent restraint stress-induced gastric ulcers in rats.

Stress causes gastric ulcer in vertebrates. In humans, growth hormone (hGH) and prolactin (hRPL) are promptly released into the circulation under the stress conditions, while in rats exposed to stress, the circulating levels of GH (rGH) are decreased and the circulating PRL (rPRL) levels are rapidly increased as in humans during stress. However, the roles of the circulating rGH and rPRL during stress are still unclear. Here we analyzed whether 22K hGH, 20K hGH or rGH, when compared to rPRL, can affect restraint stress in water (RSW)-induced gastric ulcers. Pretreatments of rats with subcutaneously (s.c.) administered rPRL or 20K hGH clearly prevented the development of the gastric injuries in rats subjected to 7 h RSW. The s.c. pretreatment with 22K hGH resulted in little cytoprotection in the rats exposed to RSW, while s.c. pretreatment with rGH showed no such protective effect against RSW-induced gastric injuries. Results suggested that rPRL and 20K hGH were acting on PRL receptor, but not on GH receptor, to prevent RSW-induced gastric injuries.