Expression and functional analysis of beta-adrenoceptor subtypes in rabbit submandibular gland.
beta-Adrenoceptors (beta-ARs) mediate important physiological functions in salivary glands. Here we investigated the expression and function of beta-AR subtypes in rabbit submandibular gland (SMG). Both beta(1)- and beta(2)-ARs, but not beta(3)-AR, were strongly expressed in rabbit SMG. beta(1)-AR proteins were widely expressed in acinar and ductal cells whereas beta(2)-AR proteins were mainly detected in ductal cells. A [(3)H]-dihydroalprenolol binding assay revealed that beta-AR B(max) was 186+/-11.9 fmol/mg protein and K(d) was 2.71+/-0.23 nM. A competitive binding assay with CGP 20712A, a beta(1)-AR antagonist, indicated that the proportion of beta(1)-AR and beta(2)-AR was 71.9% and 28.1%, respectively. Gland perfusion with the beta-AR agonist isoproterenol induced a significant increase in saliva secretion which was abolished by pretreatment with the non-selective beta-AR antagonist propranolol. Pretreatment with beta(1)- or beta(2)-AR selective antagonists, CGP 20712A or ICI 118551, diminished isoproterenol-induced increase in saliva secretion by 71.2% and 28.8%, respectively. The expression of alpha-amylase mRNA was significantly stimulated by isoproterenol, which was eliminated by propranolol and CGP 20712A. Perfusion with isoproterenol decreased alpha-amylase protein storage in SMG and increased alpha-amylase activity in saliva. These alterations became less significant after pretreatment with propranolol and CGP 20712A. Our results suggest that both beta(1)- and beta(2)-ARs are expressed in rabbit SMG. beta(1)-AR is the predominant subtype and may play an important role in regulating saliva and alpha-amylase secretion.
Li
Yu-Ming
YM
Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing 100083, China.
Zhang
Yan
Y
Xiang
Bin
B
Zhang
You-Yi
YY
Wu
Li-Ling
LL
Yu
Guang-Yan
GY
D000818:Animals; D017931:DNA Primers; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D011433:Propranolol / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013363:Submandibular Gland / Q000502:physiology*; D000516:alpha-Amylases / Q000235:genetics
D017931:DNA Primers; D012333:RNA, Messenger; D011943:Receptors, Adrenergic, beta; D011433:Propranolol; D000516:alpha-Amylases; D007545:Isoproterenol