Gastric mucosal cell proliferation during development in rats and effects of pentagastrin.

Changes in cell proliferation and cell loss in the gastric mucosa were examined during the first 4 wk of life. The effect of pentagastrin on these parameters before and after weaning was also investigated. The results revealed that DNA content of mucosa and lumen increased with age. However, when luminal DNA (an assessment of cell loss) content was expressed as percent of total mucosal DNA (referred to as percent cell loss), an inverse relationship with age was observed. The rate of mucosal DNA synthesis, measured in vitro, was found to remain elevated up to the age of 15 days and then dropped dramatically within the next 5--6 days after which it decreased slowly. The rate of mucosal DNA synthesis in 5- to 15-day-old rats was found to be 10--15 times higher than in 20- to 30-day-old rats. In 10-day-old suckling young, mucosal thymidine kinase activity was also found to be higher than in 20- to 28-day-old rats. On the other hand, total incorporation of [3H]thymidine into mucosal DNA per stomach was found to be significantly greater in 21- to 28-day-old weaned rats than in the 10-day-old suckling young. Multiple injections of pentagastrin to 28-day-old rats significantly increased mucosal DNA synthesis and thymidine kinase activity by 43 and 200%, respectively, and cell loss by 30% when compared with the saline control. The hormone did not affect DNA synthesis, thymidine kinase, or cell loss in 10-day-old rats. There were considerable increases in 20-day-old rats that were not statistically significant due to the variation of the data.