Vol 59, No 3 (2008)
Original paper
Published online: 2008-05-08
Somatostatin receptors in GH-secreting pituitary adenomas - their relationship to the response to octreotide
Endokrynol Pol 2008;59(3):196-199.
Abstract
Twenty pituitary adenomas, surgically removed from patients suffering from acromegaly, were studied. The tumours were immunostained
with anti-GH and anti-PRL antibodies and with antibodies raised against particular subtypes of somatostatin receptors (rsst1–5).
Expression of rsst immunoreactivity was scored using the following scale: 0 - negative reaction, 1 - weak reaction, 2 - moderate
reaction, 3 - strong reaction. In 15 patients in whom the GH response to the acute administration of 200 ug octreotide was tested the
correlation between the expression of rsst and the percentage of GH drop was estimated. All the tumours were GH-immunopositive and
in the majority (14/20) co-expression of PRL was also found. All the adenomas examined expressed rsst2A (20/20) and rsst5 (12/12) receptor
proteins. Receptors sst2B and rsst3 were found in all but one of the tumours examined (19/20 and 11/12, respectively). None of tumours
investigated presented rsst4 immunopositivity. The mixed (GH/PRL) adenomas showed a tendency to a higher expression of rsst2A +
+ rsst2B and a greater response to octreotide administration. A significant positive correlation was found between rsst2A + rsst2B expressions
and a drop in GH after octreotide.
To conclude, the GH-inhibiting effect of octreotide depends on the intensity of expression of both rsst2A and rsst2B. Both isoforms of rsst2 mediate the same biological response (inhibition of GH secretion) in GH-secreting and GH/PRL-secreting adenomas.
To conclude, the GH-inhibiting effect of octreotide depends on the intensity of expression of both rsst2A and rsst2B. Both isoforms of rsst2 mediate the same biological response (inhibition of GH secretion) in GH-secreting and GH/PRL-secreting adenomas.
Keywords: acromegalysomatostain receptorsoctreotide
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