Long term administration of ? -sympatheticomimetic drugs to animals such as rat, mouse and hamster causes some significant changes in parotid and submandibular glands. These changes include hypertrophy and hyperplasia of glandular tissues, intial release of amylase from glands, prevention of amylase synthesis and increase in the synthesis of a new group of proteins called proline-rich proteins (PRPS). Studies have shown that these changes induced by these drugs are mediated through interaction with the cell surface ? -adrenergic receptors. In the present study, two groups of male guinea pig and three groups of male adult albino rabbits were selected. Guinea pigs were injected i.p with isoproterenol (0.1 mg/Anim) for 20 days. Rabbits treated for 15 consecutive days with ? 1- agonist dobutamine, 60 mg/kg body wt per day or by ? 2- agonist terbutaline 40 mg/kg body wt per day respectively. Sterile distilled water was used for controls. In the end of experiment animals sacrificed and salivary glands were extirpated and weighed, then gland extracts prepared. After using isoproterenol, both parotid and submandibular glands revealed a significant increare in weights (P<0.01). The weights of the parotid glands increased significantly after both dobutamine and terbutaline treatment (P<0.01). Submandibular gland weights also, were affected significantly by terbutaline (P<0.05). Biochemical studies indicated that isoproterenol decreases the amount of total protein and amylase in parotid gland (P<0.01), but on the other hand, in submandibular gland total protein and amylase increased (P<0.01, P<0.001). Dobutamine and terbutaline increased
significantly the concentration of total protein in parotid and submandibular glands (P<0.01, P<0.05). Gland weights and total protein were not significantly affected by the two selective /3- adrenergic agonists in sublingual glands. SDS-PAGE of isoproterenol treated submandibular gland showed protein bands with molecular weights of about 14.8, 16 and 52 kds which the first two bands probably belongs to a group of proline-rich proteins. SDS-PAGE of parotid glands of dobutamine and terbutaline treated animals revealed protein bands with molecular weights of about 40, 38, 35, 34, 32, 27 and 40, 38, 35, 34 kds respectively. SDS-PAGE of submandibular and sublingual of terbutaline treated animals showed protein bands with molecular weights of about 20, 18 and 16 kds respectively. These differences in guinea pig probably shows that the number of ? 1 and ? 2 adrenergic receptors may be varied in both parotid and submandibular secretory cells. On the other hand, it seems that in guinea pig ? 1 - receptors are mainly in parotid salivary gland but in submandibular gland ? 2-receptors are predominent. The present investigation in rabbit probably suggests that the ? - adrenergic receptors may be higher in number in the rabbit parotid gland that in the submandibular or sublingual. On the other hand, ?1 subtype is dominant in rabbit parotid gland. These observations, also, suggest that the proteins may probably belong to proline-rich proteins
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