Submandibular gland acinar cells express multiple alpha1-adrenoceptor subtypes.
We evaluated an acinar cell line (SMG-C10) cloned from rat submandibular glands as a possible model for alpha(1)-adrenoceptor regulation of submandibular function. alpha(1)-Adrenoceptors are subdivided into three subtypes called alpha(1A), alpha(1B), and alpha(1D), which can be distinguished from one another by their differential affinity values for subtype-selective alpha(1)-adrenoceptor antagonists. Thus, alpha(1)-adrenoceptor subtypes in SMG-C10 cells were characterized with reverse transcription-polymerase chain reaction (RT-PCR) and [(3)H]prazosin binding in side-by-side experiments with native submandibular glands. RT-PCR identified mRNAs for alpha(1A)-, alpha(1B)-, and alpha(1D)-adrenoceptors in SMG-C10 cells and submandibular glands. The inhibition of [(3)H]prazosin binding by 5-methylurapidil (alpha(1A)-selective) was biphasic and fit best to a two-site binding model with 40 +/- 8% high (K(iH))- and 60 +/- 10% low (K(iL))-affinity binding sites in SMG-C10 cells, and 76% high- and 24% low-affinity binding sites in submandibular glands. Respective K(iH) and K(iL) values for 5-methylurapidil were 1.9 +/- 0.4 and 100 +/- 30 nM in SMG-C10 cells and 3.2 +/- 0.8 and 170 +/- 20 nM in submandibular glands. BMY-7378 [8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4.5]decane-7,9-dione dihydrochloride (alpha(1D)-selective)] bound with low affinity in SMG-C10 cells and submandibular glands with K(i) values of 81 +/- 20 and 110 +/- 20 nM, respectively. Chloroethylclondine, an irreversible alkylating agent selective for alpha(1B) adrenoceptors, reduced the density of [(3)H]prazosin binding sites by 42 and 26% in SMG-C10 and submandibular membranes, respectively. Thus, SMG-C10 cells and submandibular glands are similar in expressing receptor protein for alpha(1A)- and alpha(1B)-adrenoceptor subtypes, establishing SMG-C10 cells as a potential model for alpha(1)-adrenoceptor-mediated secretion.
Bockman
Charles S
CS
Department of Pharmacology, Creighton University School of Medicine, 2500 California Plaza, Omaha, NE 68178, USA. cbockman@creighton.edu
Bruchas
Michael R
MR
Zeng
Wanyun
W
O'Connell
Kelly A
KA
Abel
Peter W
PW
Scofield
Margaret A
MA
Dowd
Frank J
FJ
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D011224:Prazosin / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism*; D018341:Receptors, Adrenergic, alpha-2 / Q000235:genetics / Q000378:metabolism*; D013363:Submandibular Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014316:Tritium
D000317:Adrenergic alpha-Antagonists; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D014316:Tritium; C051731:chlorethylclonidine; D003000:Clonidine; D011224:Prazosin