Effect of Isoproterenol on Polyamine Metabolism in Mouse Salivary Glands

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Abstract
Changes in polyamine metabolism during growth-stimulation of mouse salivary glands by isoproterenol were investigated. In parotid gland, the activity of ornithine decarboxylase [EC 4.1.1.17] increased very rapidly after administration of the drug and reached a maximum after 8 hr. The maximal enzyme activity was about 40-fold higher than that of the unstimulated gland. Thereafter the enzyme activity decreased abruptly and returned to normal after 20 hr. The activity of putrescine-dependent S-adenosyl-L-methionine decarboxylase [EC 4.1.1.50] also increased after this treatment and reached a maximum after 12 hr, the peak activity being about 7-fold higher than the control activity. Then it decreased and returned to nearly the normal level after 28 hr. The putrescine level varied sharply in parallel with the changes in ornithine decarboxylase activity. The spermidine concentration was elevated between 12 and 16 hr after isoproterenol administration, while the rate of incorporation of labeled uridine into total cellular RNA reached a maximum after 16 hr. These iso-proterenol-dependent metabolic alterations were also detected in the submaxillary gland, but they were more delayed and less pronounced than those in the parotid gland, like the changes in weight of the gland. Pilocarpine, a powerful secretagogue of saliva but not a stimulant of DNA synthesis in salivary glands, had much less effect than isoproterenol in inducing ornithine decarboxylase in the parotid gland. From these results, it is concluded that changes in polyamine metabolism in the salivary glands after isoproterenol administration are closely related to DNA synthesis, rather than to secretion of saliva.

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