CHANGES IN THE ELECTROCARDIOGRAM AND HEART CHOLINE ESTER CONTENT OF THIAMINE-DEFICIENT AND PAIR-FED RATS
The choline ester content of trichloroacetic acid extracts of thiamine-deficient, pair-fed, and normal rat hearts was determined by differential assays on the eserinized frog rectus and guinea pig gut. The thiamine-deficient hearts contained about 3.5 times more choline ester than the normal hearts, while the pair-fed ones about twice as much. It is concluded from results of differential assays and filter paper chromatography of the trichloroacetic acid extracts that the chief, probably the only, choline ester in all the three groups is acetyl choline. It is also pointed out that the possibility of the presence of a mixture of pyruvyl, propionyl, and acetyl choline in the thiamine-deficient heart could not be excluded with these methods. Bradycardia and increased R voltage develop both in thiamine-deficient and in pair-fed rats, but are more pronounced in the former group. When the three groups of rats, normal, pair-fed, and thiamine-deficient, were treated as a single population a positive correlation was found between R voltage and total ACh equivalent and an inverse correlation between heart rate and ACh equivalent. The trichloroacetic acid extracts of rat hearts of all the three groups contain a positive inotropic substance (or substances) and substances which absorb ultraviolet light, most probably nucleic acid derivatives, which interfere with the frog heart assay of choline esters. The ultraviolet absorbing compounds are the bearers of most of the positive inotropic activity. These can be separated from the negative inotropic choline esters by filter paper chromatography.