Studies on LM protein appearing in submandibular glands of isoproterenol-treated rats. III. Some aspects of its formation.

Abstract

A single stimulation with isoproterenol (IPR) resulted in a 1.5-fold increase in the total protein in saliva from rat submandibular glands at 1 day after the injection. Large mobile (LM) protein began to be secreted from the glands early after IPR injection, reaching a maximum at 2 days after injection, when the total protein in saliva had returned to the normal level. The secretion of this protein continued for 22 days after injection, indicating that the life of LM protein template is long or that the effect of IPR remains during this period. The increase of LM protein after IPR stimulation was markedly suppressed by β-adrenergic receptor blocking drugs. When both an α-adrenergic receptor blocking drug and adrenaline were injected together into rats, a small amount of the LM protein appeared and an increase in the wet weight of submandibular glands was seen. Repeated injection of these drugs resulted in a remarkable increase of LM protein. These results suggest that the appearance of LM protein was not a consequence of direct action of IPR but was due to a stimulatory effect of IPR on β-adrenergic receptors and that chronic blocking of α-adrenergic receptors has a significant stimulative effect on the production of LM protein through β-adrenergic receptors.