Human TRH receptor messenger ribonucleic acid levels in normal and adenomatous pituitary: analysis by the competitive reverse transcription polymerase chain reaction method.
OBJECTIVE
Little is known about the mechanism of diversity in in-vivo hormonal responsiveness to TRH in patients with functional pituitary adenomas. In order to clarify the relation between the responsiveness to TRH and TRH receptor messenger ribonucleic acid (mRNA) expression, we attempted to measure TRH receptor mRNA levels in human pituitary adenoma tissues by competitive reverse transcription polymerase chain reaction (RT-PCR) method.


METHODS
Pituitary tissue samples were obtained at autopsy from 5 patients without pituitary disease. Pituitary adenoma tissue samples were obtained at surgery from 18 patients with pituitary adenoma (4 non-functioning, 8 prolactinoma, 4 acromegaly, 1 Cushing's disease and 1 FSH producing adenoma).


METHODS
Partial TRH receptor cDNA from a human GH producing adenoma cDNA library was amplified by PCR under low stringency conditions using primers encoding the transmembrane domains III and VI of pituitary TRH receptor cDNA. The partial sequence of the amplified cDNA determined by a dideoxy-chain termination method was identical to the corresponding sequence of human TRH receptor cDNA. A competitor was generated by deleting the inner 111 bp from the amplified TRH receptor cDNA and subcloning. RNA extracted from human pituitary was reverse transcribed and co-amplified with competitor by PCR under higher stringency conditions. The TRH receptor mRNA levels, expressed as the relative intensity against the amplified levels of competitor, were compared among various pituitary tissues.


RESULTS
The relative TRH receptor mRNA levels of pituitary tissues in patients without pituitary disease were detectable and variable (M +/- SD) (0.370 +/- 0.231, n = 5), and slightly but not significantly lower than those in patients with pituitary tumours (0.598 +/- 0.265, n = 18). In patients with prolactinoma, the relative levels of TRH receptor mRNA were quite variable (0.02-1.170, 0.604 +/- 0.358, n = 8) and not correlated with PRL responsiveness to TRH (responder 0.457; non-responder 0.340-0.950). In patients with acromegaly, TRH receptor mRNA was detectable not only in the paradoxical GH responder to TRH (0.718) but also in the non-responder (0.758 and 0.765). In one patient with Cushing's disease, a relatively low level of TRH receptor mRNA could be detected (0.415). In the patient with a FSH producing tumour whose plasma FSH did not respond to TRH, a small amount of TRH receptor mRNA was detectable (0.447).


CONCLUSIONS
In patients with functioning pituitary adenomas, hormonal responsiveness to TRH in vivo might not be assessable by TRH receptor mRNA levels in the adenoma cells.
Kaji
H
H
Third Division Department of Medicine, Kobe University School of Medicine, Japan.
Xu
Y
Y
Takahashi
Y
Y
Abe
H
H
Tamaki
N
N
Chihara
K
K
D000236:Adenoma / Q000737:chemistry*; D000293:Adolescent; D000328:Adult; D000368:Aged; D001483:Base Sequence; D017931:DNA Primers; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D010902:Pituitary Gland / Q000737:chemistry*; D010911:Pituitary Neoplasms / Q000737:chemistry*; D016133:Polymerase Chain Reaction; D015175:Prolactinoma / Q000737:chemistry; D012333:RNA, Messenger / Q000032:analysis*; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000032:analysis* / Q000235:genetics
D017931:DNA Primers; D012333:RNA, Messenger; D018025:Receptors, Thyrotropin-Releasing Hormone