Background/Aims:L-Glutamine (L-gln) is a conditionally essential amino acid which is consumed by certain tissues like the intestine in large amounts as energy source during critical illness. Apart from nutritive action, recent data suggest a link to heat-shock protein (hsp) induction. We investigated the effect of L-gln on hsp72 expression in the intestinal cell line Caco-2 under basal and heat-shock conditions and compared it with related amino acids. Methods: Total cellular protein was extracted and separated by SDS-PAGE. Immunoblots were performed with anti-hsp72 followed by chemiluminescence detection and densitometric scanning. Results: Following heat shock, hsp72 protein expression increased by 72 and 53% at 2 and 4 mmol/l L-gln, respectively, compared to heat shock alone (p < 0.05). Under basal conditions a limited increase occurred only at 8 mmol/l L-gln (p < 0.01). Levels remained unaffected when related amino acids including alanine, glutamate or glycine were supplemented under basal and heat-shock conditions. Similarly, the nonmetabolizable glutamine analogue DON or the toxic metabolite L-pyroglutamate did not induce hsp72. Conclusion: We conclude that the glutamine-mediated effect may be specifically attributed to the metabolic action of L-gln.