Presence and regulation of a truncated proopiomelanocortin gene transcript in rat pancreatic islets.
The demonstration of proopiomelanocortin-(POMC-) derived peptides in the endocrine pancreas suggests a local biosynthesis of these peptides. Using Northern blot analysis we demonstrated a 800 nucleotide POMC-like mRNA species. The POMC-like mRNA was demonstrable in a part of the pancreatic islets by the in situ hybridization technique. A small number of single cells within the exocrine pancreas were also found to give positive hybridization signals. Isolated islets were incubated under normoglycemic conditions with dibutyryl-cAMP (3mM) or dexamethasone (0.1mM) for 4 h. Dibutyryl-cAMP significantly (p < 0.01) increased the POMC-like mRNA content to 177 +/- 39.1% of the control whereas dexamethasone decreased it to 66.9 +/- 11.4% of the control. In vivo treatment of adult rats with 80 micrograms dexamethasone over 3 days showed also a reduction of the POMC-like mRNA level in the islets. In conclusions, the POMC gene is expressed in adult rat islets and can be regulated by dexamethasone and dibutyryl-cAMP. Whether the truncated POMC-like mRNA reported here is the source of the biosynthetic POMC-like products detected in the islets is not yet known.
Hummel
A
A
Institut für Biochemie, Universität Greifswald.
Lendeckel
U
U
Hahn von Dorsche
H
H
Zühlke
H
H
D000818:Animals; D015152:Blotting, Northern; D003994:Bucladesine / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation; D017403:In Situ Hybridization; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D011333:Pro-Opiomelanocortin / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics*; D051381:Rats
D012333:RNA, Messenger; D003994:Bucladesine; D011333:Pro-Opiomelanocortin; D003907:Dexamethasone