Open AccessSTIMULATION OF DNA SYNTHESIS BY ISOPROTERENOL IN RAT SUBMANDIBULAR GLAND DURING POSTNATAL GROWTH
Author(s) -
Barka Tibor,
Chang William W.,
Noen Hendrika
Publication year - 1973
Publication title -
cell proliferation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.647
H-Index - 74
eISSN - 1365-2184
pISSN - 0960-7722
DOI - 10.1111/j.1365-2184.1973.tb01602.x
Subject(s) - medicine , dna synthesis , endocrinology , submandibular gland , stimulation , hyperplasia , muscle hypertrophy , cell growth , thymidine , biology , dna , protein biosynthesis , chemistry , microbiology and biotechnology , biochemistry
The post‐natal growth of rat submandibular gland and the effect of isoproterenol on this process were studied. Between 2 and 42 days of age the DNA content of the gland increased linearly but the increase in RNA and protein content was more rapid after 29 days of age. The RNA: DNA and protein: DNA ratio increased linearly with age. The proliferative activity, measured by the incorporation of tritiated thymidine, was maximum in the gland of 7‐day‐old rats. It declined steadily to a low level in 42‐day‐old rats. A single injection of isoproterenol had no effect on thymidine incorporation in 2‐day‐old rats. The drug, however, stimulated DNA synthesis in older animals and the degree of stimulation was inversely correlated with the proliferative activity in control rats. Small doses of isoproterenol given to rats for 4 days between 2 and 5 days of age produced a hypertrophy of the submandibular gland. The same treatment between 7 and 10 days of age caused both hypertrophy and hyperplasia of the gland. It is concluded that both the regulation of growth and the regulation of induced cell proliferation are a function of cellular differentiation and that cell proliferation can be induced only in cells that reached a certain degree of differentiation.