title: Postnatal development of sarcolemmal invaginations in right atrial myocardium of the rat.
abstract: Postnatal development of the sarcolemmal invaginations of right atrial cells of the rat has been studied using standard fixation combined with tannic acid mordanting. T tubules were seen to form at Z lines as simple tubular invaginations starting at the 14th postnatal day. T tubules were present in most cells by the 18th postnatal day but, as in the adult, were restricted to peripheral regions. Also, between the 16th and 18th postnatal day a proliferation of caveolae was seen, both as single vesicles and as complexes with up to a dozen caveolae sharing the same neck. The caveolar complexes persisted in the adult and did not seem to contribute significantly to the formation of the T tubules. Dyadic couplings were seen to become more abundant as T tubules and caveolae proliferated. These findings are discussed in relation to transsarcolemmal Ca2+ movements and excitation-contraction coupling during postnatal development.
mesh_terms: D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development*; D005260:Female; D006321:Heart / Q000254:growth & development*; D006325:Heart Atria; D008297:Male; D009206:Myocardium / Q000166:cytology / Q000648:ultrastructure; D051381:Rats / Q000254:growth & development*; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000502:physiology*