Human satietin: rapid development of tolerance and its specificity to feeding behavior in rats

Semipurified human satietin (SP hSAT) significantly (p less than 0.05) reduced food intake for each of five consecutive days when injected intraperitoneally (2 mg/kg/day). Tolerance developed rapidly during the second and third days of injection but food intake of those animals receiving the highest doses of Sp hSAT (1 and 2 mg/kg/day) remained significantly below (p less than 0.05) that of the saline-injected animals. Food intake of rats receiving doses of 0.5 and 0.25 mg/kg/day Sp hSAT was below that of the saline-treated group for the first two days of injection (p less than 0.05) but not thereafter. Water intake fell in all satietin-treated groups on the first day of injection, thereafter, it was similar to the saline-treated group. In a second study Sp hSAT (1, 0.5, 0.25 mg/kg/day) was continuously infused IP by Alzet pumps. All doses of Sp hSAT significantly reduced food intake below that of the saline-treated group for the entire 7 days of infusion (p less than 0.05); water was not affected except on the first day of infusion (p greater than 0.01). In a third study, injection of purified human satietin (p hSAT) (2 mg/kg, IP) in fasted rats (24 hr) had no effect on water consumption either during fast or 24 hr postfast (p greater than 0.05). In a fourth study p hSAT was continuously heated to 37 degrees C. Aliquots were taken each day and injected (IP) into 4 naive rats (total of 24 rats) for a total of 6 days of heating (120 hr).(ABSTRACT TRUNCATED AT 250 WORDS)