Growth Hormone and Somatostatin Gene Expression in Pituitary Adenomas with Active Acromegaly and Minimal Plasma Growth Hormone Elevation

Some patients with active acromegaly have elevated plasma IGF-I concentrations with only minimal elevation of plasma GH. We compared adenomatous GH and SRIH expression in 3 such patients (patients No. 1, 2 and 3; basal plasma GH level less than 4 micrograms/l) and in 3 acromegalic patients with high basal plasma GH level (patients No. 4, 5 and 6; 51.7 +/- 16.1 micrograms/l, mean +/- SEM). By immunocytochemistry, all the tumours proved to be somatotropic adenomas. At the ultrastructural level, signs of low secretory activity were observed in adenomas from patients No. 2 and 3. Perifused adenoma cells of patients No. 1, 2 and 3 released very little GH compared with those of patients No. 4, 5 and 6 (1 +/- 0.37 vs 51.5 +/- 34.1 micrograms x (10(-6) cells) x min-1, p less than 0.001). Adenoma SRIH content was 65.7 and 30.6 pg/mg proteins in patients No. 1 and 2, whereas it was undetectable in the others (patients No. 4, 5 and 6). Northern blot analysis showed that the GH gene was poorly expressed in the adenomas from patients No. 1, 2 and 3 compared with the adenomas from patients No. 4, 5 and 6. SRIH mRNA was detected in all 6 adenomas. However, the signal was more intense in the adenomas from patients No. 1, 2 and 3 than in those from patients No. 4, 5 and 6.(ABSTRACT TRUNCATED AT 250 WORDS)