Developmental enhancement of secretory response to isoproterenol coupled with increases in β-adrenoceptor density and Gs protein function in rat parotid tissues

• Published in: Mechanisms of ageing and development Vol. 104; no. 1; pp. 75 - 90
• Main Authors: Ishikawa, Yasuko, Chen, Cang, Eguchi, Takafumi, Skowronski, Mariusz T, Ishida, Hajime
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier Ireland Ltd 01.08.1998; Elsevier Science
• Subjects: Adenosine Diphosphate Ribose - metabolism; Adenylate cyclase; Adenylyl Cyclases - metabolism; Adrenergic beta-Agonists - metabolism; Adrenergic beta-Agonists - pharmacology; Animals; Biological and medical sciences; Colforsin - pharmacology; Culture Techniques; Development; Development. Metamorphosis. Moult. Ageing; Female; Fundamental and applied biological sciences. Psychology; GTP-Binding Protein alpha Subunits, Gs - metabolism; GTP-Binding Proteins - metabolism; Guanine nucleotide binding proteins; Guanosine Triphosphate - metabolism; Isoproterenol - metabolism; Isoproterenol - pharmacology; Male; Organ Size; Parotid Gland - drug effects; Parotid Gland - metabolism; Parotid glands; Rats; Rats, Wistar; Receptors, Adrenergic, beta - metabolism; Receptors, Muscarinic - metabolism; Vertebrates: anatomy and physiology, studies on body, several organs or systems; β-Adrenoceptors; Development; Adenylate cyclase; Parotid glands; β-Adrenoceptors; Guanine nucleotide binding proteins; Agonist; Isoprenaline; Amylase; Parotid gland; Rat; Digestive system; Enzyme; Secretion; Rodentia; Guanine nucleotide; Phosphorus-oxygen lyases; Salivary gland; Secretory cell; Lyases; β-Adrenergic receptor; Binding protein; Vertebrata; Mammalia; Animal; Age
• ISSN: 0047-6374; 1872-6216
• DOI: 10.1016/S0047-6374(98)00054-2

The β-adrenergic agonist, isoproterenol (IPR), stimulated more significantly and sensitively amylase secretion from both the tissues of 7- and 56-day-old rats than a cholinergic agonist, carbachol, at the same concentration. The EC 50 value of amylase secretion with IPR decreased significantly during development but that with carbachol did not change. Estimation by measuring bindings of [ 3H]dihydroalprenolol and [ 3H]quinuclidynylbenzylate indicated the marked increases in the numbers of both β-adrenoceptors and muscarinic receptors in the tissues during development. The affinity of β-adrenoceptors for the agonist was also enhanced during development, but that of muscarinic receptors for the agonist was not. These developmental changes in the number and affinity of β-adrenoceptors and muscarinic receptors paralleled those in amylase secretory response of the tissues to their agonists. The response of adenylate cyclase (AC) of the tissues to 1 μM IPR was steadily enhanced after birth. In contrast, the response of AC to 1 μM forskolin was high until 14 days old, but markedly decreased at 28 days old and thereafter maintained this level. The increase in cholera toxin-catalyzed ADP-ribosylation (AR) of stimulatory GTP binding proteins (Gs proteins) in the tissues was apparent at 14 days old, reaching a maximum at 56 days old and thereafter decreasing with age. On the other hand, pertussis toxin-catalyzed AR of inhibitory GTP binding proteins (Gi proteins) did not change after birth. Thus, the ratio of apparent levels of Gs to Gi proteins increased significantly after birth, reaching a maximum at 56 days old, but decreased rapidly till 84 days old and thereafter maintained this level. These changes in the ratio paralleled those in the response of AC to IPR. These results showed that the rapid and marked increases in the number and affinity of β-adrenoceptors and the ratio of apparent levels of Gs to Gi proteins in rat parotid tissues during development had a key role in the enhancement of the secretory response of the tissues to β-agonists.