Bombesin receptor gene expression in rat pancreatic acinar AR42J cells: transcriptional regulation by glucocorticoids.
OBJECTIVE
This study investigated the correlation between glucocorticoid-regulated gene expression of the bombesin receptor (BR) and cellular sensitivity to bombesin stimulation in the rat pancreatic acinar cell line AR42J.


METHODS
BR gene expression was assessed using a cloned complementary DNA probe and radioligand binding assays. Intracellular Ca2+ mobilization was assessed by dual wavelength spectrophotometry using fura-2 in single cells.


RESULTS
Dexamethasone resulted in a rapid dose- and time-dependent decrease of BR messenger RNA levels with maximal inhibition to 25% +/- 2% of controls (n = 4) after 6 hours of hormone treatment. BR messenger RNA half-life was approximately 120 minutes and was not affected by dexamethasone pretreatment; nuclear run-on analysis showed a decreased transcription rate of the BR to approximately 25% of control after hormonal treatment. Radioligand binding studies showed a time-dependent decrease of specific bombesin binding to 25% +/- 8% of control after 48 hours of hormone treatment. Down-regulation of BR gene expression by dexamethasone resulted in a time- and dose-dependent decrease of intracellular Ca2+ mobilization after bombesin stimulation compared with untreated controls.


CONCLUSIONS
Glucocorticoids decrease BR gene transcription. The subsequent decrease in cellular BR number renders AR42J cells less sensitive for bombesin-stimulated intracellular Ca2+ mobilization.
Department of Gastroenterology, Medizinische Klinik und Poliklinik, Klinikum Steglitz, Berlin, Germany.
S
S
Rosewicz
K
K
Detjen
A
A
Kaiser
N
N
Prosenc
J
J
Cervos-Navarro
E O
EO
Riecken
H
H
Haller
D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects*; D005938:Glucocorticoids / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D010179:Pancreas / Q000737:chemistry* / Q000166:cytology* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D018004:Receptors, Bombesin / Q000032:analysis* / Q000235:genetics* / Q000502:physiology; D011965:Receptors, Glucocorticoid / Q000032:analysis / Q000502:physiology; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects*
D005938:Glucocorticoids; D007457:Iodine Radioisotopes; D012333:RNA, Messenger; D018004:Receptors, Bombesin; D011965:Receptors, Glucocorticoid; D003907:Dexamethasone; D001839:Bombesin; D002118:Calcium