Expression of growth hormone receptor isoform exon-3-excluding and exon-3-retaining messenger RNAs in peripheral lymphocytes from normal and acromegalic subjects.
OBJECTIVE
To determine the expression of two isoforms of the growth hormone (GH) receptor (GHR), which differ by the presence (GHR3+) or absence (GHR3-) of exon 3, and their correlation with circulating GH and insulin-like growth factor I (IGF-I) in normal subjects and in acromegalic patients.


METHODS
The expression of GHR isoforms was determined by reverse-transcriptase polymerase chain reaction in lymphocytes from 12 normal subjects and from 11 patients with acromegaly. The levels of GHR mRNA were normalized to those of beta-actin, and ratios were calculated to assess the relative levels of expression.


RESULTS
All samples showed expression of both GHR isoforms, but the expression of GHR3+ and GHR3- was similar in acromegalic patients (6.0+/-1.7 vs. 8.3+/-2.0%, mean +/- SE). In contrast, in healthy subjects, GHR3- was the predominant isoform (11.8+/-3.0 vs. 5.1+/-0.68%; p<0.05), and the levels of expression of GHR3- correlated significantly with IGF-I.


CONCLUSIONS
These data demonstrate coexpression of both GHR isoforms under normal and pathological conditions; however, GHR3- is the predominant form in normal subjects and shows a negative correlation with IGF-I levels.
Ochoa
Raquel
R
Endocrine Research Unit, National Medical Center, Instituto Mexicano del Seguro Social, México, DF, México.
Zárate
Arturo
A
Cerbón
Marco A
MA
Salcedo
Mauricio
M
López
Ricardo
R
Galván
Rosa E
RE
Hernández
Marcelino
M
D000172:Acromegaly / Q000235:genetics / Q000378:metabolism*; D000328:Adult; D001483:Base Sequence; D005091:Exons; D005260:Female; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000097:blood; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008214:Lymphocytes / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000097:blood; D011986:Receptors, Somatotropin / Q000097:blood* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018972:Insulin-Like Growth Factor Binding Protein 3; D020033:Protein Isoforms; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone