Experimental effects of thiamine diphosphate and monophosphate on the heart

Abstract

Continuing the study on the action of the phosphorilated derivates of thiamine on the heart, the results obtained with the diphosphate of thiamine (DPT) and the monophosphate of thiamine (MPT) are presented. Previously the action of the triphospate of thiamine (TPT) was studied (LuíˆCAS-Ga- ij.ego and Ard\iz-Soi.ciiaga) (1).

The techniqucs which were used were : isolated heart with a Stranb cannule on the frog ; «in situ» heart on the cat andStarling’s heart-lung preparation on the dog. On the dog and on the cat the arterial pressure, the duration of the electric stimulus, the auricular bcat and the ventricular beat have been registercd.

It has been seen that DPT and MPT produce a inotropic effect on the heart of the frog at all the concentrations used (1G“,; to 10 ‘) so much more inarked the greater the concentra­ ron. Smaller concentrations (10-7 and 10-K) do not have any action.

It has also been seen that DPT has a protective action over an excess of Ca in Ringer’s solution, its addition to the solu-ticn (10 1 concentration) prcvcnts the absolute systolic failure, as happcns when therc is no DPT in Straub’s cannule (fig 2). Its protective action against the Ba ion is doubtful and it does not have any action over an excess of K in the Ringer so­ lution.

MPT does not have any protective action against the three ions.

The action of both substances on hearts of frogs subjccted to electric cxcitation has been studied and it has been seenthat if it is true that the duration of cardiac inhibition di- minishes, its recuperation is -more energctic, as can be seen by the amplitude bf the heart beats once the cardiac failure is overcomed (fig. 3 and 4). DPT has shown itself to be supe­ rior to MPT.

On the hearts of the cat fibrilation has been provoked by the direct application of an induced current aud it has been seen that the injection of DPT and MPT can diminish the duration of fibrilation previouslj’ produced on a control trialon the sanie cat and using the same duration of electric excita- tion. Other times fibrilation can be made reversible when in a control trial the cat was unable to overeóme it by itself (fig. 5 and 6).

'file results obtained with DPT haré bccn superior to those of MPT.

In the eardio-respiratory preparation of a dog we liare obtained through the addition of DPT and MP'I to the circu- lating blood, a greater resístame to fibrilation by the heart

caused by stimulation with an induced current. Pzven so, the time margins are very small and the results more difficult to evalúate than 011 the cat. Here also the rcsults obtained with DPT are better than with MPT.

These results are comparable to those found on <>ur previous work, aJready mentioned, on the action of TPT and it is thought that this, as already is known, once in the organism looses a phosphoric group and beconies DPT. This phosphoric group could act as an energy donator, whiíc DP'I would keep

its own function, being this the reason why the effect of TPT is superior to that of DPT by itself.

Cocarboxylase, according to Kiessi.ixg and I.ixdaiii. (4), can act as a donator of phosphate groups.

MPT can loose its phosphate group and afterwards the resulting thiamine can phosphorilate itself with a phosphate group, becoming cocarboxylase or DPT ; all of what would explain that, effectively, we should have found a number of positive results with AIPT although inferior to those with TPT and DPI'.