Ileum toxicus

Crude and three diethyl ether extracted, acetone treated, fractions were isolated from large-scale cultures of Gambierdiscus toxicus. Crude extracts at. 04 mg/ml inhibited the histamine contraction response in smooth muscle of the guinea pig ileum. Three semi-purified fractions at 5 ng/ml, effectively inhibited the guinea pig ileum preparation. Two of these fractions followed Michaelis-Menten kinetics for a competitive inhibition. The third fraction inhibited in a non-reversible manner. This study has established the presence of three lipid extracted toxins in toxicus, outlined a method for their assay in small quantities, and identified at least two of the effects of these toxic extracts in animals. 

This paper is a report on the lipid extracted toxins from toxicus and their effect on isolated guinea pig ileum prepara-tions. This paper also proposes the use of this preparation for quantification of two of the lipid extracted toxins. 

N (N 0 0 ri (N 0 1 00 On N of GT-3 by stating both the dose inhibition from the control as DCI50 Table II. Summary of results from assays of ESAP and GT-1, GT-2, toxicus and time to achieve a 50% (Table II). mouse and guinea pig ileum and GT-3 from Gambierdiscus ... 

Relationship of Fractions to Other Toxins. Our initial extractions of tHe toxic fractions are tHe same as that of Tachibana, ( ) and others. Thus, the isolation of GT-la and GT-lb correspond exactly to the initial steps in the isolation of ciguatoxin by Scheuer ( ). The isolation of GT-2b and GT-2c and their similar action on the ileum preparation, causes us to conclude that they are either a more polar form of GT-1 or a modification of GT-1 accomplished during the extraction procedures. GT-3, it appears, would most likely correspond to a carry over of a maitotoxin-1ike fraction from the initial ether-water separation. Without any chemical confirmation, however, these are only tentative identifications. Indeed, toxins extracted from Caribbean isolates of toxicus, could be quite different from those extracted from Pacific isolates. 

Effects of GT-4 on Ileum. A constant infusion of GT 4 at nanogram levels produced exactly the same effects as previously described for the WSAP. Parallel assays with GT-4 and WSAP revealed that 2.8 ng/ml of GT-4 caused the same rate of decline of activity as 5.0 pg/ml of WSAP. These parallel assays of WSAP and GT-4 provided an efficient means for the estimation of a purification factor. Purification of the toxin was 1,785 fold. Using this value we projected an estimate for the LD50 of GT-4 as 0.62 pg/kg mouse. This value comes quite close to the calculated LD50 value reported for maitotoxin (0.17 pg/kg), isolated from toxicus from the Pacific. 

The guinea pig ileum assay appears to be able to distinguish three separate lipid soluble toxins obtained from G. toxicus cultures. These toxic fractions isolated from G. toxicus show inhibition of the guinea pig ileum preparations (Miller et al. 1984). 

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