Response of jejunal Na+, K+-ATPase to 5-hydroxytryptamine in young and adult rats: effect of fasting and refeeding.
The present study is aimed to evaluate the effects of 5-hydroxytryptamine (5-HT) upon jejunal Na+,K+-ATPase in young (20-day-old) and adult (60-day-old) rats, and determine the effect of food intake on the response of the sodium pump to the amine. Basal Na+,K+-ATPase activity in jejunal epithelial cells from young rats was twice that in adult animals and responded to 5-HT with stimulation. In adult rats, fasting reduced by 25% basal jejunal Na+, K+-ATPase activity, whereas in young rats, no such change was observed. The sensitivity of jejunal Na+,K+-ATPase to 5-HT in young fasted rats was similar to that observed in fed animals. The effect of refeeding in young rats was a 2-fold increase in jejunal Na+, K+-ATPase activity, this being accompanied by insensitivity to 5-HT. In adult rats, refeeding was accompanied by an increase in jejunal Na+,K+-ATPase activity. It is concluded that the stimulatory effect of 5-HT upon jejunal Na+,K+-ATPase activity is a phenomenon dependent on both age and type of diet. In young rats, it is the food intake that plays an important role in development of insensitivity of Na+,K+-ATPase to stimulation by 5-HT, while in adult animals fasting or fasting followed by refeeding does not play a major role in regulating its sensitivity to the amine.
Lucas-Teixeira
V
V
Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal.
Serrão
M P
MP
Soares-Da-Silva
P
P
D000367:Age Factors; D000818:Animals; D004435:Eating / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects; D005215:Fasting / Q000502:physiology*; D016166:Free Radical Scavengers / Q000032:analysis / Q000493:pharmacokinetics*; D006897:Hydroxyindoleacetic Acid / Q000032:analysis; D007583:Jejunum / Q000737:chemistry / Q000201:enzymology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000032:analysis / Q000493:pharmacokinetics*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D016166:Free Radical Scavengers; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D000254:Sodium-Potassium-Exchanging ATPase