A case of antibody formation against octreotide visualized with ¹¹¹In-octreotide scintigraphy

A case of antibody formation in a patient with carcinoid syndrome is described. The patient was treated with octreotide in dosages up to 1.5 mg/day. Serum samples were analysed for the presence of octreotide antibodies before and after 20 months of octreotide treatment. In-vivo 111In-octreotide scintigraphy was performed before and during therapy, and after antibodies had developed. Before treatment, no serum antibodies against octreotide were detected. After 20 months of treatment, they were detectable up to a 1:115 serum dilution. The serum binding of 125I-Tyr3-octreotide was blocked by adding excess unlabelled Tyr3-octreotide, indicating the presence of specific octreotide antibodies. Before treatment, a normal distribution of radioactivity in the spleen and kidneys, irregular uptake in the liver due to metastases, and a hot spot in the lower abdomen were found during 111In-octreotide scintigraphy. After antibodies had developed, increased radioactivity over the heart and high background radioactivity in the abdomen with only faint visualization of the spleen, liver, and kidneys were found, indicating a prolonged presence of 111In-octreotide in the blood resulting from its being bound to antibodies. Increased radioactivity was also seen at the injection sites of the drug in the upper legs. In-vitro incubation of biopsy tissue from this site with 125I-Tyr3-octreotide revealed diffuse guanosine triphosphate (GTP) independent specific binding non-G-protein linked binding of labelled octreotide. This report describes the characteristic abnormalities during in-vivo 111In-octreotide scintigraphy in a patient with octreotide antibodies. These consisted of high background radioactivity due to prolonged circulation of antibody coupled 111In-octreotide together with visualization of the injection sites, which most probably results from local accumulation of antibodies.</p

A case of antibody formation against octreotide visualized with ¹¹¹In-octreotide scintigraphy

A case of antibody formation in a patient with carcinoid syndrome is described. The patient was treated with octreotide in dosages up to 1.5 mg/day. Serum samples were analysed for the presence of octreotide antibodies before and after 20 months of octreotide treatment. In-vivo 111In-octreotide scintigraphy was performed before and during therapy, and after antibodies had developed. Before treatment, no serum antibodies against octreotide were detected. After 20 months of treatment, they were detectable up to a 1:115 serum dilution. The serum binding of 125I-Tyr3-octreotide was blocked by adding excess unlabelled Tyr3-octreotide, indicating the presence of specific octreotide antibodies. Before treatment, a normal distribution of radioactivity in the spleen and kidneys, irregular uptake in the liver due to metastases, and a hot spot in the lower abdomen were found during 111In-octreotide scintigraphy. After antibodies had developed, increased radioactivity over the heart and high background radioactivity in the abdomen with only faint visualization of the spleen, liver, and kidneys were found, indicating a prolonged presence of 111In-octreotide in the blood resulting from its being bound to antibodies. Increased radioactivity was also seen at the injection sites of the drug in the upper legs. In-vitro incubation of biopsy tissue from this site with 125I-Tyr3-octreotide revealed diffuse guanosine triphosphate (GTP) independent specific binding non-G-protein linked binding of labelled octreotide. This report describes the characteristic abnormalities during in-vivo 111In-octreotide scintigraphy in a patient with octreotide antibodies. These consisted of high background radioactivity due to prolonged circulation of antibody coupled 111In-octreotide together with visualization of the injection sites, which most probably results from local accumulation of antibodies.</p

17-β-Estradiol-dependent regulation of somatostatin receptor subtype expression in the 7315b prolactin secreting rat pituitary tumor in vitro and in vivo

In the present study, we have investigated the role of estrogens in the regulation of somatostatin receptor subtype (sst) expression in 7315b PRL- secreting rat pituitary tumor cells in vitro and in vivo. sst were undetectable in freshly dispersed cells of the transplantable 7315b tumor. When 7315b cells were cultured in medium containing 10% FCS, the number of high affinity sst increased with prolonged culture time. However, when the medium was supplemented with 10% horse serum (HS) instead of FCS, no sst were detectable on 7315b cells even after three weeks of culturing. In contrast to HS, FCS contains high E2-levels (HS, 8 pM; FCS, 134 pM). The antiestrogen tamoxifen (0.5 μM) significantly inhibited the sst number to 50.5% of the value of untreated FCS-grown cells, suggesting that E2 stimulates sst expression in 7315b rat pituitary tumor cells. E2 (l0 nM) induced a rapid increase in sst number in HS-grown 7315b cells. Octreotide (1μM) significantly inhibited PRL release and the intracellular PRL concentration of 7315b cells that were cultured in medium supplemented with FCS or with HS + l0 nM E2 but not in HS alone. This indicates that the sst present on these cells are biologically active. RT-PCR analysis revealed that none of the five currently known sst subtypes were present in freshly dispersed 7315b pituitary tumor cells. The expression of sst2- and sst3- messenger RNA (mRNA) was unequivocally correlated to the presence of E2 because these sst subtypes were detected only in cells that were cultured for7 and 14 days in medium supplemented with FCS or with HS + 10 nM E2. sst1, sst4 and sst5 messenger RNA could not be detected. The 7315b tumor itself synthesizes and secretes huge amounts of PRL. The high PRL levels in tumor-bearing rats inhibit the ovarian E2-production. No detectable E2 levels could be measured in the serum of 7315b tumor-bearing rats. The sc administration of 20 μg/day E2-benzoate normalized the circulating E2 levels in 7315b tumor- bearing rats. Moreover, E2-treatment indeed induced sst expression in vivo as shown by ligand binding studies using membrane homogenates and [125I- Tyr3]-octreotide as radioligand and by autoradiography on tissue sections. In agreement with the in vitro studies, the expression of the sst2 subtype was established by RT-PCR analysis in 7315b tumors of E2-treated rats. However, in contrast to the in vitro studies. E2-treatment did not effectuate the expression of the sst3 subtype, suggesting that the in vitro stimulus of E2 is stronger. In conclusion: 1) sst2 and sst3 expression in the 7315b rat prolactinoma model is primarily dependent upon the presence of estrogens; 2) the antihormonal action of octreotide in 7315b tumor cells in vitro is mediated via the sst2 and/or sst3 subtypes; 3) the absence of sst expression in vivo can be explained by the hormonal environment of the 7315b tumor cells. The 7315b tumor cells in vivo may down-regulate their own receptor status via their host, because of the ensuing hyperprolactinemia results in a hypo-estrogenic state.</p

Visualization of the thymus by substance P receptor scintigraphy in man

Substance P, an 11-amino acid neuropeptide, has an important role in modulating pain transmission through neurokinin 1 and 2 receptors. Substance P and other tachykinins may also play a role in the pathogenesis of inflammatory diseases. In this study we present the results concerning the metabolism of the substance P analogue [111In-DTPA-Arg1]-substance P in man, as well as the visualization of the thymus in patients with immune-mediated diseases. Twelve selected patients were investigated, comprising five with inflammatory bowel disease, one with ophthalmic Graves' disease, one with sclerosing cholangitis, one with Sjogren's syndrome, one with rheumatoid arthritis, one with systemic lupus erythematosus and two with myasthenia gravis. During and after intravenous administration of 150-250 MBq (2.5-5.0 μg) [111In-DTPA-Arg1]-substance P, blood pressure, heart rate and oxygen saturation were monitored. Radioactivity was measured in blood, urine and faeces during the 48 h after injection. Planar and single-photon emission tomographic images were obtained 4 and 24 h after injection. After administration of [111In-DTPA-Arg1]-substance P a transient flush was observed in all patients. Degradation of [111In-DTPA-Arg1] -substance P started in the first minutes after administration, resulting in a half-life of 10 min for the total plasma radioactivity, and of 4 min for the intact radiopharmaceutical, as identified with high-performance liquid chromatography. Urinary excretion accounted for &gt;95% of the radioactivity within 24 h post injection, and up to 0.05% was found in the faeces up to 60 h. In all patients uptake of radioactivity was found in the areolae mammae (in women), liver, spleen, kidneys and urinary bladder. In eight patients a high uptake of [111In-DTPA-Arg1]-substance P was observed in the thymus. We conclude that, despite its short half-life. [111In-DTPA-Arg1]-substance P, a new radiopharmaceutical, can be used to visualize the thymus. This may contribute to the investigation of the role of thymus in immune-mediated diseases. In addition, inflammatory sites in various diseases could be visualized.</p

Visualization of the thymus by substance P receptor scintigraphy in man

Substance P, an 11-amino acid neuropeptide, has an important role in modulating pain transmission through neurokinin 1 and 2 receptors. Substance P and other tachykinins may also play a role in the pathogenesis of inflammatory diseases. In this study we present the results concerning the metabolism of the substance P analogue [111In-DTPA-Arg1]-substance P in man, as well as the visualization of the thymus in patients with immune-mediated diseases. Twelve selected patients were investigated, comprising five with inflammatory bowel disease, one with ophthalmic Graves' disease, one with sclerosing cholangitis, one with Sjogren's syndrome, one with rheumatoid arthritis, one with systemic lupus erythematosus and two with myasthenia gravis. During and after intravenous administration of 150-250 MBq (2.5-5.0 μg) [111In-DTPA-Arg1]-substance P, blood pressure, heart rate and oxygen saturation were monitored. Radioactivity was measured in blood, urine and faeces during the 48 h after injection. Planar and single-photon emission tomographic images were obtained 4 and 24 h after injection. After administration of [111In-DTPA-Arg1]-substance P a transient flush was observed in all patients. Degradation of [111In-DTPA-Arg1] -substance P started in the first minutes after administration, resulting in a half-life of 10 min for the total plasma radioactivity, and of 4 min for the intact radiopharmaceutical, as identified with high-performance liquid chromatography. Urinary excretion accounted for &gt;95% of the radioactivity within 24 h post injection, and up to 0.05% was found in the faeces up to 60 h. In all patients uptake of radioactivity was found in the areolae mammae (in women), liver, spleen, kidneys and urinary bladder. In eight patients a high uptake of [111In-DTPA-Arg1]-substance P was observed in the thymus. We conclude that, despite its short half-life. [111In-DTPA-Arg1]-substance P, a new radiopharmaceutical, can be used to visualize the thymus. This may contribute to the investigation of the role of thymus in immune-mediated diseases. In addition, inflammatory sites in various diseases could be visualized.</p

IGF-I Bioactivity in an Elderly Population: Relation to Insulin Sensitivity, Insulin Levels, and the Metabolic Syndrome

OBJECTIVE - There is a complex relationship between IGF-I, IGF binding proteins, growth hormone, and insulin. The IGF-I kinase receptor activation assay (KIRA) is a novel method for measuring IGF-I bioactivity in human serum. We speculated that determination of IGF-I bioactivity might broaden our understanding of the IGF-I system in subjects with the metabolic syndrome. The purpose of our study was to investigate whether IGF-I bioactivity was related to insulin sensitivity and the metabolic syndrome. RESEARCH DESIGN AND METHODS - We conducted a cross-sectional study embedded in a random sample (1,036 elderly subjects) of a prospective population-based cohort study. IGF-I bioactivity was determined by the IGF-I KIRA. Categories of glucose (in)tolerance were defined by the 2003 American Diabetes Association criteria. Insulin sensitivity was assessed by homeostasis model assessment. The Adult Treatment Panel III definition of the metabolic syndrome was used. RESULTS - In subjects with normal fasting glucose and impaired fasting glucose, IGF-I bioactivity progressively increased with increasing insulin resistance, peaked at fasting glucose levels just below 7.0 mmol/l, and dropped at higher glucose levels. Mean IGF-I bioactivity peaked when three criteria of the metabolic syndrome were present and then declined significantly when five criteria of the metabolic syndrome were present. CONCLUSIONS - We observed that IGF-I bioactivity was related to insulin sensitivity, insulin levels, and the metabolic syndrome. Our study suggests that there exists an inverse U-shaped relationship between IGF-I bioactivity and number of components of the metabolic syndrome. This observation contrasts with previous results reporting an inverse relationship between total IGF-I and components of the metabolic syndrome

A CLOSE CORRELATION BETWEEN THE INHIBITORY EFFECTS OF INSULIN‐LIKE GROWTH FACTOR‐I AND SMS 201‐995 ON GROWTH HORMONE RELEASE BY ACROMEGALIC PITUITARY TUMOURS IN VITRO AND IN VIVO

In the present study we compared the in‐vitro effects of IGF‐I and SMS 201–995 on GH release by cultured tumour cells obtained from seven acromegalic patients with the preoperative in‐vivo GH dynamics, including the acute response to 50μg SMS 201–995 subcutaneously. IGF‐I and SMS 201–995 inhibited GH release during a 24 h incubation in four and five of the seven tumour cell preparations, respectively. The inhibitory effect of SMS 201–995 was greater than that exerted by IGF‐I (P &lt; 0.01). There was a close correlation between the in‐vitro inhibitory effects of IGF‐I and SMS 201–995 (P &lt; 0.01). In addition, the acute inhibitory effect of 50 μg SMS 201–995 on circulating GH levels in vivo correlated with the inhibitory effects in vitro of both SMS 201–995 (P &lt; 0.01) and IGF‐I (P &lt; 0.05). The inhibitory effects of IGF‐I and SMS 201–995 on GH release in vitro were shown to be additive in two of four tumours. There was no relation between the in‐vitro effects of IGF‐I and/or SMS 201–995 and several in‐vivo parameters, including fluctuations in GH levels, sleep‐induced GH release, a paradoxical increase of GH in response to TRH, and the circulating IGF‐I and PRL levels. In conclusion: (1) there is a close correlation between the sensitivity of GH release by cultured human adenoma cells to IGF‐I and SMS 201–995. (2) There is also a close correlation between the in‐vivo inhibitory effect on GH release of SMS 201–995 and the in‐vitro inhibitory effects of both SMS 201–995 and IGF‐I. (3) A subgroup of acromegalic patients harbour pituitary tumours in which the qualitative regulation of hormone secretion is similar to that of normal GH secretion.</p

A COMPARISON BETWEEN THE EFFECTS OF SMS 201–995, BROMOCRIPTINE AND A COMBINATION OF BOTH DRUGS ON HORMONE RELEASE BY THE CULTURED PITUITARY TUMOUR CELLS OF ACROMEGALIC PATIENTS

The in‐vivo reaction of the plasma GH concentration to the administration of the somatostatin analogue SMS 201‐995, bromocriptine and their combination were compared with the in‐vitro effects of both compounds and their combination on GH release and the GH tumour cell content of 9 acromegalic patients. Exposure of cultured GH‐secreting pituitary tumour cells for 4–96 h to SMS 201‐995 showed a variable, but in all instances during longer incubations statistically significant inhibition of GH release, which paralleled the sensitivity of GH secretion to the drug in vivo. This inhibitory effect on GH release was in two of the eight tumours accompanied by a decrease in the GH tumour cell content after 24‐72 h of culture. These changes either reflect an inhibition of GH synthesis and/or an increase in intracellular breakdown (crinophagy) of GH and might be the basis for the tumour shrinkage which has been observed in about half of the acromegalic patients during long‐term SMS 201‐995 therapy. The inhibitory effects of bromocriptine on GH secretion were antagonized by haloperidol, while the inhibitory effect of SMS 201‐995 was not affected by the dopamine receptor antagonist. This suggests that the effects of SMS 201‐995 and bromocriptine are mediated via separate mechanisms involving different receptors. Additive but no potentiating inhibitory effects of both drugs on GH release were observed in a group of six patients in vivo and in three of six tumours in vitro.</p