Effect of pilocarpine on protein synthesis in the hamster submandibular gland.

Abstract

Many histomorphological studies of the secretory cycle in salivary glands have been done (0. JARvI, Z Zellforsch 30:156-170, 1939; A. AMSTERDAM, I. OHAD, and M. SCHRAMM, J Cell Biol 41:753-773, 1969). However, little is known about concomitant rates of protein synthesis. Junqueira (Sekretion und Exkretion, Berlin: Springer-Verlag, 1965, p 31) has suggested that the synthetic phase of the secretary cycle is linked to the extrusion phase by a positive feedback system. The present investigation studied the effect of pilocarpine-induced secretion on protein synthesis in acinar and granular duct cells of the hamster submandibular gland. Young adult, male, golden Syrian hamsters (Cricetus auratus) were fasted for 48 hours but were allowed water ad libitum. Each of 23 hamsters received an intraperitoneal injection of 0.1 mg/100 gm body weight of pilocarpine hydrochloride in 1.0 ml of physiologic saline. Four control hamsters were given 1.0 ml of saline alone. At various intervals (Fig 1, 2) after injection, each animal received a single intravenous injection of 5 Rtc/gm body weight of L-leucine-4,5-3H in 0.01 N HCl.* All hamsters were killed 30 minutes after isotope injection, and the submandibular glands were fixed in Bouin-Hollande solution. Autoradiographs of 5 micrometer ([tm) sections were prepared using liquified NTB 2 emulsion.t Autoradiographs were analyzed, with the aid of an ocular reticle, by counting silver grains over the cytoplasm of each of 50 acinar and granular duct cells of similar size and shape. The statistical method of moving averages was used to describe all curves (J. P. GUILFORD, Fundamental Statistics, 1956). Studies have demonstrated that only a negligible amount of free or sonically bound radioactive leucine is retained in Bouin-fixed histologic sections after amino acid injection (B. DROZ and H. WARSHAWSKY, J Histochem Cytochem 11:426-435, 1963) and it is generaliy accepted that the radioactive particles recorded by the nuclear emulsion are emitted by labeled leucine molecules that have been incorporated into the structure of newly synthesized proteins. Pilocarpine produced an accelerated flow of saliva with no apparent changes in the gross or microanatomic appearance of the submandibular gland. The acinar and granular duct cells