Effects of antimicrotubular agents on the secretory process of rat submandibular acinar cells
Kawai, K.
Kaibogaku Zasshi. Journal of Anatomy 56(6): 484-498
1981
ISSN/ISBN: 0022-7722 PMID: 7336877 Document Number: 181398
The effects of antimicrotubular agents (colchicine and vinblastine) on acinar cells of the rat submandibular gland were studied by EM. The discharge of secretory granules of the acinar cells was stimulated by an i.p. injection of isoproterenol (8 mg/100 g body wt). Colchicine (0.5-1.5 mg/100 g body wt) or vinblastine (1-2 mg/100 g body wt) was administered via an i.m. injection. Female Wistar rats were divided into 3 groups and treated as follows: pretreatment with any of the antimicrotubular agents for 1 h followed by isoproterenol injection for 40 min; 8 h after isoproterenol injection combined with treatment of any of the antimicrotubular agents for 2, 4 or 6 h; 8 h after isoproterenol injection combined with treatment of colchicine or vinblastine for 6 h, followed by isoproterenol reinjection for 30 min. The control for each group was untreated with the antimicrotubular agents. The submandibular gland was processed by conventional methods for EM, and a part of the tissues was subjected for the histochemical demonstration of thiamine pyrophosphatase activity by the method of Novikoff and Goldfischer. The effects of colchicine and those of vinblastine on the ultrastructure of the acinar cells appeared to be almost similar. Microtubules were always observed in the Golgi area of acinar cells untreated with the antimicrotubular agents, however, the treatment with the antimicrotubular agents caused the disappearance of microtubules. Pretreatment with the antimicrotubular agents did not inhibit the discharge of secretory granules caused by isoproterenol stimulation. At 8 h after isoproterenol injection, well-developed Golgi apparatus occupied the supranuclear area of the acinar cells and the accumulation of newly synthesized secretory granules was observed in the luminal cytoplasm. The treatment with the antimicrotubular agents caused vesiculation and fragmentation of the Golgi lamellae. The Golgi apparatus became reduced in size, disrupted and scattered throughout the cytoplasm. Thiamine pyrophosphatase activity was retained in a few innermost lamellae. Newly formed secretory granules located not only in the luminal cytoplasm and in the Golgi regions, but also in the basal cytoplasm. The degree of ultrastructural modification was augmented as the duration after the treatments with the antimicrotubular agents was prolonged. Though newly synthesized secretory granules in the apical regions were discharged by isoproterenol reinjection, those scattered in the cytoplasm were not discharged. Morphological alterations of the rough endoplasmic reticulum was not clearly detected. Microtubules may be involved in: the organization of the Golgi apparatus, the maintenance of secretory granules orientation within the cytoplasm and the transport of secretory granules from the Golgi apparatus to the luminal cytoplasm.