title: Effect of hypothermia on intestinal adaptation and carcinogenesis in the rat.
abstract: Postoperative hyperplasia enhances experimental intestinal carcinogenesis, but the effects of nonsurgical adaptation are uncertain. The tropic and tumour-promoting potentials of moderate hypothermia were tested in two groups of male Sprague-Dawley rats housed at 10 degrees C for 30 weeks. One group (n = 10) received a 6-week course of azoxymethane (total dose 90 mg kg-1). The second group (n = 7) acted as hypothermic controls. Another 2 groups maintained at 22 degrees C received azoxymethane (n = 15) or served as normothermic controls (n = 15). Overall food intake was 42% higher in the hypothermic groups, yet at sacrifice mean body weight was 13% lower (P less than 0.01). Hypothermia and azoxymethane combined to produce the following increases in crypt cell production rate (CCPR), as determined stathmokinetically: duodenum 170%, jejunum 172%, ileum 74%, proximal colon 227% (P = 0.05-0.01). Independently hypothermia had no effect, but azoxymethane produced 76-156% increases in CCPR throughout the large intestine. Although hypothermia did not affect overall tumour yield, the mean diameter of proximal colonic tumours was increased by 65% (P less than 0.05). In rats receiving azoxymethane, hypothermia stimulates cell proliferation in the small bowel as well as in the proximal colon, where it has a correspondingly mild cocarcinogenic effect.
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D001397:Azoxymethane; D001835:Body Weight; D002452:Cell Count; D003080:Cold Temperature / Q000009:adverse effects*; D003110:Colonic Neoplasms / Q000209:etiology; D004435:Eating; D006965:Hyperplasia; D007413:Intestinal Mucosa / Q000187:drug effects / Q000473:pathology*; D007414:Intestinal Neoplasms / Q000139:chemically induced / Q000209:etiology* / Q000473:pathology; D007421:Intestine, Small / Q000166:cytology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012004:Rectal Neoplasms / Q000209:etiology
chemical_list: D001397:Azoxymethane