Thiol-induced discharge of acontial nematocytes.
The discharge of nematocytes, the stinging cells of Coelenterata, is a poorly understood phenomenon. In particular, little is known about the chemical stimuli that trigger the discharge. In this paper, we show that thiols are able to initiate the nematocyst discharge in isolated nematocytes. Among the thiols tested, reduced glutathione and cysteine were found to be the most effective. The effect of glutathione was likely two-fold: it formed mixed disulfides with membrane thiols, as shown by the ability of the mercapto-blocking reagent iodoacetamide to abolish its action; and it bound to the membrane through the glutamate moiety, as demonstrated by competitive experiments with free glutamate. Glutathione triggered the discharge at concentrations higher than those sufficient to activate the feeding response of Coelenterates. However, our results demonstrate for the first time that the modification of membrane thiols by selective agents may be a key event in the discharge of nematocytes.
La Spada
Giuseppina
G
Department of Physiology and Pharmacology, University of Messina, Salita Sperone 31, 98166 Messina, Italy.
Sorrenti
Giuseppe
G
Soffli
Andrea
A
Montaleone
Bruno
B
Marino
Angela
A
Musci
Giovanni
G
D000477:Alkylating Agents / Q000494:pharmacology; D000818:Animals; D037421:Anthozoa / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D001733:Bites and Stings; D002628:Chemoreceptor Cells / Q000187:drug effects / Q000378:metabolism; D003545:Cysteine / Q000494:pharmacology; D004220:Disulfides / Q000378:metabolism; D005978:Glutathione / Q000494:pharmacology; D006710:Homocysteine / Q000494:pharmacology; D007460:Iodoacetamide / Q000494:pharmacology; D010084:Oxidation-Reduction; D010396:Penicillamine / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000494:pharmacology*
D000477:Alkylating Agents; D004220:Disulfides; D013438:Sulfhydryl Compounds; D006710:Homocysteine; D005978:Glutathione; D010396:Penicillamine; D003545:Cysteine; D007460:Iodoacetamide