Stereospecific effects of tryptophan on gastric emptying and hunger in humans.
The amino acid tryptophan (tryp) is a potent inhibitor of gastric emptying in both animals and humans. Animal studies suggest that this effect may be specific for the L-enantiomer. The effects of D- and L-tryptophan on gastric emptying, intragastric distribution and appetite in humans were evaluated. Ten volunteers ingested 300 mL of either L-tryp (50 mmol/L), D-tryp (50 mmol/L) or normal saline labelled with 99mTc sulfur colloid on three occasions, separated by between 3 and 7 days. Hunger and fullness were measured with a visual analogue scale at -2, 15, 30 and 60 min after ingestion of each drink. Saline emptied faster from the stomach than both L-tryp and D-tryp (P < 0.05) and D-tryp emptied faster than L-tryp (P < 0.005). Emptying from the proximal stomach was fastest for saline (P < 0.05) and faster for D-tryp than L-tryp (P < 0.005). Emptying from the distal stomach was faster for saline than both D- and L-tryp (P < 0.05). A reduction in hunger (P < 0.05) and a non-significant trend for an increase in fullness were observed after all three drinks. At 60 min, fullness was greater after L-tryp than after ingestion of D-tryp (P < 0.01). These observations indicate that the effect of tryptophan on gastric emptying in humans is stereospecific, consistent with the concept that stereospecific receptors for tryptophan exist in the human small intestine.
Carney
B I
BI
Department of Medicine, Royal Adelaide Hospital, South Australia.
Jones
K L
KL
Horowitz
M
M
Sun
W M
WM
Hebbard
G
G
Edelbroek
M A
MA
D000328:Adult; D001066:Appetite / Q000187:drug effects; D005260:Female; D005746:Gastric Emptying / Q000187:drug effects*; D006801:Humans; D006815:Hunger / Q000187:drug effects*; D008297:Male; D012527:Satiation / Q000187:drug effects; D012965:Sodium Chloride; D013237:Stereoisomerism; D013671:Technetium Tc 99m Sulfur Colloid; D013997:Time Factors; D014364:Tryptophan / Q000494:pharmacology*
D012965:Sodium Chloride; D013671:Technetium Tc 99m Sulfur Colloid; D014364:Tryptophan