CHROMOSOME ACTIVITY AND CELL FUNCTION IN POLYTENIC CELLS .2. FORMATION OF SECRETION IN SALIVARY GLANDS OF CHIRONOMUS

RNA synthesis was inhibited in larvae of Chironomus tentans with actinomycin D. After inhibition for 24 or 48 h, injected 3H- or 14C-amino acids were still incorporated into secretory proteins of the salivary gland at rates similar to the normal rate. In salivary glands of Chironomos pallidivittatus, special-cell granules were missing after protein synthesis had been blocked for about 12 h. These granules were still present if RNA synthesis was inhibited for even 48 h. By treatment of larvae with pilocarpin, glands were completely depleted of their secretory products. Larvae recovered from this treatment in actinomycin solutions as well as in fresh culture water within 48 h. Secretory products, including special cell granules, were present in similar amounts in the glands of larvae recovered under both conditions. Inhibition of RNA synthesis caused a decrease in the rate of protein synthesis at the beginning of the last instar. It did not seem to interfere with the production of special-cell granules at this stage. It is concluded that the production of secretory proteins in the salivary glands of Ch. tentans and pallidivittatus is supported by stable mRNA, and that the stability of this RNA, presumably Balbiani ring RNA, does not change during development. © 1969.