MULTIPLE TYROSINE-HYDROXYLASE TRANSCRIPTS AND IMMUNOREACTIVE FORMS INTHE RAT - DIFFERENTIAL EXPRESSION IN THE ANTERIOR-PITUITARY AND ADRENAL-GLAND

Several regulatory neurofactors, classically associated with the hypot halamus, may be synthesized in the anterior pituitary (AP), Dopamine ( DA) is the main prolactin-inhibiting factor. Its de novo synthesis in the normal AP has not been proved, although the TH transcript has been previously demonstrated by RT/PCR in the AP, We investigated tyrosine hydroxylase (TH) gene expression at both the protein and mRNA levels in the AP of normal random cycling female rats and in a catecholaminer gic tissue, the adrenal gland (AG), The Western blot analysis of AP ho mogenates revealed two irnmunoreactive forms of TH in the AP, both dif fering from the TH present in the AG, RT/PCR products from AP and AG m RNA were subcloned and sequenced, In addition to the full-length form, we identified two TH transcripts generated by alternative splicing ei ther involving the use of a new alternate splice-donor site within exo n 2 or skipping exon 11, The form lacking exon 11 was not isolated fro m the AG, In the AP, all three forms were present, Although the AP con tained the full-length TH mRNA, the expected size protein was not dete cted, Thus, there is alternative splicing of the TH primary transcript , and putative additional posttranslational regulation may yield TH pr oteins with no enzymatic activity, at least in non-catecholaminergic t issues. (C) 1995 Wiley-Liss, Inc.