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In vivo detection of somatostatin receptors in gastro-entero-pancreatic (GEP) endocrine tumours using 111In-pentatreotide
176 IN VIVO DETECTION OF SOMATOSTATIN RECEPTORS IN GASTRO-ENTERO-PANCREATIC (GEP) ENDOCRINE TUMOURS USING 11HN-PENTATREOTIDE. Jamar F, Leners N, Fiasse R, Pauwels S. Depts of Nuclear Medicine and Gastroenterology, University of Louvain Medical School, B-1200 Brussels, Belgium. The presence of somatostatin receptors on most GEP endocrine tumours offers the possibility for their in vivo visualization using a radiolabelled somatostatin analogue, n lln-pentatreotide (OctreoScanRlll, Mallinckrodt Medical, Holland). In order to evaluate the diagnostic value of OctreoSean~lll scintigraphy, we investigated 28 patients with histology proven GEP tumours: 13 carcinoids, 7 gastrinomas, 2 insulinomas, 2 MEN-I, 3 nonsecreting tumours, 1 motilinoma. Planar acquisitions were obtained 4 and 24 h after injection of -200MBq OctreoScanRlll and SPECT was performed at 24 h. Scintigraphic results were compared with those obtained by morphological imaging methods (CT-scan, US and MRI). OctreoScanR111 showed lesions in 25 of 28 patients whereas morphological imaging was positive in 22 patients. Among the 3 negative scintiscans, 2 patients (1 gastrinoma, 1 MEN-l) had also negative morphological imaging studies and 1 insulinoma was positive at US only. In 4 of the 25 positive scintiscans, no lesions were detected by the other imaging modalities. The primary tumour was visualized in 12 patients by scintigraphy and in 7 patients by morphological imaging. Local tumour recurrence was scintigraphically detected in 6 cases among which only 3 were found with the other techniques. Twentyseven metastatic sites (13 hepatic) were shown by scintigraphy compared to 21 (12 hepatic) with the morphological imaging methods. In conclusion, OctreoScanR111 scintigraphy is a sensitive method for GEP tumour detection providing additional information compared to the morphological imaging methods. It allows to image primary and recurrent tumours as well as metastatic spread during a single diagnostic procedure. Beside its diagnostic value, the test could predict the potential benefit of octreotide therapy.
IN VIVO EFFECT OF O X Y N T O M O D U L I N ON GASTRIC ACID SECRETION: EVIDENCE FOR SEVERAL PATHWAYS. Jarrousse C, Caries-Bonnet C, Niel H, Bataille D. Centre CNRS-INSERM de Pharmacologie Endocrinologie, 34094 Montpellier, France O x y n t o m o d u l i n (OXM)~ the 37-aminoacid peptide synthesized in intestinal L cellsj takes part in the negative control of gastric acid secretion (GAS). To analyze its minimal active structure, we compared the activity of two C-terminal fragments on GAS in conscious rats p r o v i d e d with a chronic gastric fistula. GAS was either stimulated by histamine (0.4 m g / k g / h ) or, in a physiological manner, by a liquid meal consisting in 14 ml milk per os. In the latter test, the gastric content was drained out 20 rain after the beginning of food intake and the H + content measured. Peptides were I.V. perfused over the 20 min period following swallowing. Histamine-induced GAS (108 + 4 ~tmol H ÷ / 2 0 min) was significantly inhibited by bolus injected OXM (60 p m o l / k g ) , OXM-[19-37] (85 p m o l / k g ) or N-acetyl-OXM-[3037] (1.5 n m o l / k g ) up to 28%, 30% and 28%, respectively. Meal-induced GAS was significantly inhibited by 29% after OXM perfusion (1 n m o l / k g / h ) and by 22% after OXM-[19-37] (6 n m o l / k g / h ) , whereas N-Acetyl-OXM[30-37] (180 n m o l / k g / h ) was without effect. N o n e of these peptides modified the volume of collected milk, suggesting no change in gastric emptying. O u r results indicate that the C-terminal octapeptide of OXM, minimal active structure on histamine-stimulated GAS, is inactive in the milk-meal test, unlike longer fragments. They suggest that OXM and its related peptides act through several pathways, one of which being shared by the C-terminal octapeptide.
IN VIVO EFFECT OF O X Y N T O M O D U L I N ON GASTRIC ACID SECRETION: EVIDENCE FOR SEVERAL PATHWAYS. Jarrousse C, Caries-Bonnet C, Niel H, Bataille D. Centre CNRS-INSERM de Pharmacologie Endocrinologie, 34094 Montpellier, France O x y n t o m o d u l i n (OXM)~ the 37-aminoacid peptide synthesized in intestinal L cellsj takes part in the negative control of gastric acid secretion (GAS). To analyze its minimal active structure, we compared the activity of two C-terminal fragments on GAS in conscious rats p r o v i d e d with a chronic gastric fistula. GAS was either stimulated by histamine (0.4 m g / k g / h ) or, in a physiological manner, by a liquid meal consisting in 14 ml milk per os. In the latter test, the gastric content was drained out 20 rain after the beginning of food intake and the H + content measured. Peptides were I.V. perfused over the 20 min period following swallowing. Histamine-induced GAS (108 + 4 ~tmol H ÷ / 2 0 min) was significantly inhibited by bolus injected OXM (60 p m o l / k g ) , OXM-[19-37] (85 p m o l / k g ) or N-acetyl-OXM-[3037] (1.5 n m o l / k g ) up to 28%, 30% and 28%, respectively. Meal-induced GAS was significantly inhibited by 29% after OXM perfusion (1 n m o l / k g / h ) and by 22% after OXM-[19-37] (6 n m o l / k g / h ) , whereas N-Acetyl-OXM[30-37] (180 n m o l / k g / h ) was without effect. N o n e of these peptides modified the volume of collected milk, suggesting no change in gastric emptying. O u r results indicate that the C-terminal octapeptide of OXM, minimal active structure on histamine-stimulated GAS, is inactive in the milk-meal test, unlike longer fragments. They suggest that OXM and its related peptides act through several pathways, one of which being shared by the C-terminal octapeptide.