Specific inhibition of the binding of the taste stimulus, L-alanine, by sulphydryl reagents, in Ictalurus punctatus.
1. Taste receptors for L-alanine and L-arginine in the channel catfish, Ictalurus punctatus, are differentially reactive to N-ethylmaleimide (NEM) and p-chloromercuribenzenesulphonic acid (pCMBS). 2. The binding of L-[3H]alanine by a sedimentable membrane fraction (Fraction P2) isolated from taste epithelium was inhibited by both NEM and pCMBS while the binding of L[3H]arginine was unaffected. 3. Inhibition of the binding of L-[3H]alanine by pCMBS was reversible with dithiothreitol (DTT). 4. NEM (10(-3) M) inhibited multi-unit neural responses to both 10(-4) M L-alanine and 10(-4) M L-arginine, while pCMBS had little effect on neural responses. 5. Pretreatment of intact taste epithelium before the preparation of Fraction P2 with NEM caused strong inhibition of L-[3H]alanine binding, while pretreatment with pCMBS caused weak inhibition. 6. The presence of L-alanine during the reaction of pCMBS or NEM with taste plasma membranes did not substantially protect against the inhibition of L-[3H]alanine binding.
Bryant
B P
BP
Monell Chemical Senses Center, Philadelphia, PA 19104.
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D000409:Alanine / Q000037:antagonists & inhibitors* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D004347:Drug Interactions; D004848:Epithelium / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D007059:Ictaluridae; D008024:Ligands; D009420:Nervous System / Q000187:drug effects; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D013649:Taste / Q000502:physiology*
D008024:Ligands; D013439:Sulfhydryl Reagents; D002731:4-Chloromercuribenzenesulfonate; D005033:Ethylmaleimide; D000409:Alanine