CYTOCHEMICAL LOCALIZATION OF CHOLINESTERASE IN EMBRYONIC RABBIT CARDIAC MUSCLE

Abstract

Cardiac muscle of rabbit embryos from day 9 through day 18 of gestation was studied by a modification of the Koelle-Friedenwald copper thiocholine technique for the localization of cholinesterase activity. In the earlier stages of development a cholinesterase, presumed to be acetylcholinesterase from its substrate and inhibitor specificity, is found in the abundant, randomly dispersed rough surfaced endoplasmic reticulum of the myoblast. Cytochemical end product is also occasionally found in the nuclear envelope, Golgi complex and subsarcolemmal cisternae. The localization of the enzyme first in the rough surfaced endoplasmic reticulum and Golgi complex and at later stages in the sarcoplasmic reticulum is significant with regard to the differentiation of the cardiac myocyte. Furthermore, the presence of this enzyme in contractile tissue before the appearance of nerves or nerve endings demonstrates an acetylcholine-cholinesterase system of myogenic origin.