Postnatal development of rat gastric lymphatics was studied by an enzy
me-histochemical method to elucidate the morphological changes of lymp
hatics and their relationship to maturation and function, especially i
n the glandular portion. The significant features of 5'-Nase-positive
lymphatics in distribution and structure were examined in different st
ages (within 24 hr, 4-21 days, and 2 months). Lymphatics in the greate
r curvature and anterior wall grew much slower than those in the:Lesse
r curvature and posterior wall of the stomach in newborn and infant ra
ts. Lymphatic islands isolated from the primary lymphatic networks in
the submucosa and subserosa underwent a morphological change during th
is early period. This is considered one of the basic steps in lymphati
c development. Occurrence of lymphatic networks in the deep lamina pro
pria indicates that development in the gastric wall is well characteri
zed from Day 10. With further growth and modification of lymphatics, t
he networks in the different layers formed an extensive communication
network and many lymphatic valves were found in the submucosa and subs
erosa. Pinocytotic vesicles, open junctions, and intraendothelial chan
nels were frequently detected in the mucosal and submucosal lymphatic
networks of the corpus-antrum and antrum-duodenum divisional zones in
the adult rats. These findings suggest that developing lymphatics in t
he rat stomach may represent rapidly growing tissue not only with high
5'-Nase activity but also with high adaptability for future physiolog
ical demands. (C) 1997 Academic Press.