EXPRESSION OF INHIBIN-ALPHA, AND INHIBIN-BETA(A) SUBUNIT AND ACTIVIN TYPE-II RECEPTOR MESSENGER-RNAS IN VARIOUS HUMAN PITUITARY-ADENOMAS

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.