Journal of Clinical Endocrinology & Metabolism, Vol 61, 666-671, Copyright © 1985 by Endocrine Society

ARTICLES

Specific somatostatin receptors on human pituitary adenoma cell membranes

S Ikuyama, H Nawata, K Kato, T Karashima, H Ibayashi and H Nakagaki

Specific somatostatin (SRIH) receptors on human pituitary adenoma cell membranes were characterized using [125I]Tyr11-SRIH as the radioligand. Specific binding of [125I] Tyr11-SRIH to adenoma cell membranes reached a steady state within 30 min at 25 C, and semilogarithmic analysis of the data revealed that the rate of the binding was linear at 25 C with a t1/2 of 13.2 min. Specific binding increased linearly with 5-160 micrograms plasma membrane protein. SRIH-14 and SRIH-28 inhibited [125I]Tyr11-SRIH binding to adenoma cell membranes with ID50S of 0.32 and 0.50 nM, respectively, while secretin, glucagon, gastrin, cholecystokinin-8, bombesin, TRH, LHRH, human GH-releasing factor-(1- 44)-NH2, D-Ala2-met-enkephalin, gamma-aminobutyric acid and taurine did not significantly inhibit binding. All of 13 GH-secreting adenomas investigated had specific and high affinity SRIH receptors, with a dissociation constant (Kd) of 0.80 +/- 0.15 nM (mean +/- SEM) and a maximal binding capacity (Bmax) of 234.2 +/- 86.9 fmol/mg protein (mean +/- SEM). Among five of the nonsecreting pituitary adenomas examined, two had SRIH receptors with Kd values of 0.18 and 0.32 nM and Bmax values of 17.2 and 48.0 fmol/mg protein, respectively. In the remaining three, SRIH receptors were not detected. These results indicate that GH- secreting adenomas as well as some nonfunctioning adenomas have specific SRIH receptors, and hence, the function of the adenomas could be altered by SRIH.

This article has been cited by other articles:

				M J Acosta-Gomez, M A Muros, J M Llamas-Elvira, A Ramirez, S Ortega, G Sabatel, C Ramos, and A de la Riva-Aguilar The role of somatostatin receptor scintigraphy in patients with pituitary adenoma or post-surgical recurrent tumours Br. J. Radiol., February 1, 2005; 78(926): 110 - 115. [Abstract] [Full Text] [PDF]

				A. Saveanu, G. Gunz, H. Dufour, P. Caron, F. Fina, L. Ouafik, M. D. Culler, J. P. Moreau, A. Enjalbert, and P. Jaquet BIM-23244, a Somatostatin Receptor Subtype 2- and 5-Selective Analog with Enhanced Efficacy in Suppressing Growth Hormone (GH) from Octreotide-Resistant Human GH-Secreting Adenomas J. Clin. Endocrinol. Metab., January 1, 2001; 86(1): 140 - 145. [Abstract] [Full Text]

				P. Jaquet, A. Saveanu, G. Gunz, F. Fina, A. J. Zamora, M. Grino, M. D. Culler, J. P. Moreau, A. Enjalbert, and L'H. Ouafik Human Somatostatin Receptor Subtypes in Acromegaly: Distinct Patterns of Messenger Ribonucleic Acid Expression and Hormone Suppression Identify Different Tumoral Phenotypes J. Clin. Endocrinol. Metab., February 1, 2000; 85(2): 781 - 792. [Abstract] [Full Text]

				R. J. Robbins Depot Somatostatin Analogs--A New First Line Therapy for Acromegaly J. Clin. Endocrinol. Metab., January 1, 1997; 82(1): 15 - 17. [Full Text] [PDF]