R. Demura et al., EXPRESSION OF INHIBIN-ALPHA, AND INHIBIN-BETA(A) SUBUNIT AND ACTIVIN TYPE-II RECEPTOR MESSENGER-RNAS IN VARIOUS HUMAN PITUITARY-ADENOMAS, Endocrine journal, 42(1), 1995, pp. 95-100
Inhibin and activin are known to be involved in the pituitary hormone
secretion as well as proliferation of the pituitary. We studied the ex
pression of inhibin alpha, and beta(A) subunit and activin type II rec
eptor (ACTR 2) mRNAs in human pituitary adenomas to determine the sign
ificance of inhibin and activin in pituitary hormone secretion. Tumor
tissues were homogenized immediately after resection in guanidinium th
iocyanate to extract total RNA. PCR was performed with reversely trans
cripted cDNA and respective amplification primers. DNA bands obtained
for inhibin alpha, beta(A) and ACTR 2 by agarose gel-electrophoresis w
ere 367, 285, and 389 bp, respectively. Messenger RNAs for inhibin bet
a, were demonstrated in all of the pituitary tissues studied, namely i
n 3 GH, 2 ACTH, 6 PRL and 1 FSH producing adenomas and 17 non-function
ing adenomas. Inhibin alpha mRNAs were detected in 10 of 12 functionin
g adenomas and 15 of 17 non-functioning adenomas. ACTR 2 mRNAs were fo
und in 11 out of 17 nonfunctioning adenomas, but only found in 3 out o
f 12 functioning adenomas. These results suggested local production of
activin, a homodimer of beta-subunits, and inhibin, a heterodimer of
alpha and beta subunits, in most of the pituitary adenomas regardless
of their hormone secretion. On the other hand, a significantly higher
incidence of ACTR 2 in non-functioning adenomas than in functioning ad
enomas suggested that activin had its main site of action in non-funct
ioning adenomas, which could be potential gonadotropinomas.