title: Effects of fasting and refeeding on antral, duodenal, and serum gastrin levels and on colonic thymidine kinase activity in rats.
abstract: Antral, duodenal, and serum gastrin levels and colonic thymidine kinase activity were determined in 1- to 4-day-fasted rats and after refeeding of 4-day-fasted rats for 3-24 h. The effect of pentagastrin on colonic thymidine kinase activity was also determined. Total deprivation of food caused a drastic reduction in gastrin concentrations in serum and tissues. After 4 days of fasting, serum gastrin levels in most animals fell below the present detection limit of the assay (10-15 pg/ml), and antral and duodenal gastrin levels decreased to 15 and 50% of the respective initial fed control. After 9 and 24 h of refeeding, gastrin concentration in serum and antrum had increased to about 35% of the initial fed level. On the other hand, refeeding for 3-24 h produced no significant change in duodenal gastrin concentration. Fasting for 1-4 days resulted in a 60-70% reduction in colonic thymidine kinase activity, compared to the initial fed control. Refeeding caused a prompt stimulation in the enzyme activity, which after 6 h was found to be 72% above the 4-day-fasted group. Daily injection of pentagastrin, at doses between 125 and 500 micrograms/kg, during a 4-day fasting period resulted in a significant stimulation in colonic thymidine kinase activity, compared to the saline-treated control. The maximal stimulation of an enzyme activity 90% higher than in the saline control was attained with a pentagastrin dose of 125 micrograms/kg. Higher doses decreased the maximal stimulatory effect of pentagastrin.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D003106:Colon / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004386:Duodenum / Q000378:metabolism*; D005215:Fasting; D005755:Gastrins / Q000097:blood / Q000378:metabolism*; D010418:Pentagastrin / Q000494:pharmacology; D011706:Pyloric Antrum / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013937:Thymidine Kinase / Q000378:metabolism*
chemical_list: D005755:Gastrins; D013937:Thymidine Kinase; D010418:Pentagastrin