Studies on the distribution of cholinesterases: activity in the human and dog heart.

The distribution and postnatal variation of cholinesterase (ChE) activity were studied in 25 human and 25 dog hearts. The observed distribution pattern is remarkably constant, In dog hearts, the pattern is as follows: sinus node (SN) greater than left atrium (LA) greater than right atrium (RA) greater than right ventricle (RV) congruent to left ventricle (LV). The average acetylcholinesterase (AcChE) activities as expressed in international units per g wet tissue are: 1.66 (SN), 1.14 (LA), 0.70 (RA), 0.22 (RV), and 0.21 (LV). In human hearts, the AcChE distribution follows the pattern of RA greater than LA greater than RV congruent to LV with corresponding average activities of 1.70, 1.38, 0.51, and 0.44 IU. The postnatal variation of ChE activity is most pronounced in the RS of the heart in both species. The average AcChE activity in the RA of the newborn puppies is 0.51 IU as compared with 2.27 IU in newborn infants. In the adult heart, however, the average atrial AcChE activity is nearly identical (1.02 IU) in both species. An additional difference is the large (34-64%) contribution of butyrylcholinesterase (BuChE) to the total activity in dog hearts whereas the contribution of BuChE is small (7-15%) in human hearts.