Radioimmunoassay for octapeptide analogs of somatostatin: Measurement of serum levels after administration of long-acting microcapsule formulations

Journal Article · Mon Aug 01 04:00:00 EDT 1988 · Proceedings of the National Academy of Sciences of the United States of America; (USA)

DOI:https://doi.org/10.1073/pnas.85.15.5688· OSTI ID:5563064

Mason-Garcia, M; Vaccarella, M; Horvath, J; Redding, T W; Groot, K; Orsolini, P; Schally, A V ^[1]

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1. Endocrine, Polypeptide and Cancer Institute, New Orleans, LA (USA)

The development of a long-acting delivery system for D-Phe-Cys-Tyr-D-Trp-Lys-Val-Cys-Trp-NH{sub 2} (RC-160), an octapeptide analog of somatostatin, required the establishment of a method for determining the concentration of this analog in serum during treatment. A sensitive and specific radioimmunoassay (RIA) for RC-160 was developed and used for following the rate of liberation of this peptide from microcapsules of poly(DL-lactide-coglycolide). Antibodies were generated in a rabbit against RC-160 conjugated to bovine serum albumin with glutaraldehyde. At an antiserum dilution of 1:100,000, the antibodies bound approximately 25% of added radiolabeled RC-160. Somatostatin octapeptide analogs that had a disulfide bridge showed crossreactivity with the antiserum, but analogs without the disulfide bridge and other peptides tested did not crossreact. The minimum detectable dose of RC-160 was 10 pg. Intra- and interassay coefficients of variation ranged from 9.1% to 12.8% and from 14% to 30%, respectively. The RIA was suitable for direct determination of RC-160 in serum. Eleven prototype batches of microcapsules were tested in rats, and the rate of release of the analog from the microcapsules was followed. An improved batch of microcapsules made from RC-160 pamoate maintained high serum levels of RC-160 for more than 30 days after intramuscular injection. The RIA should be of value for monitoring levels of this analog in serum during long-term therapy.

• OSTI ID: 5563064
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America; (USA), Journal Name: Proceedings of the National Academy of Sciences of the United States of America; (USA) Vol. 85:15; ISSN 0027-8424; ISSN PNASA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ACCURACY
ANIMALS
ANTIBODIES
BETA DECAY RADIOISOTOPES
BIOASSAY
BLOOD SERUM
CHEMICAL REACTIONS
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC TECHNIQUES
DISEASES
ELECTRON CAPTURE RADIOISOTOPES
ENDOCRINE DISEASES
HALOGENATION
IMMUNOASSAY
IMMUNOLOGY
IMMUNOTHERAPY
INTERMEDIATE MASS NUCLEI
IODINATION
IODINE 125
IODINE ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MAMMALS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PEPTIDES
POLYPEPTIDES
PROTEINS
RABBITS
RADIOASSAY
RADIOIMMUNOASSAY
RADIOIMMUNODETECTION
RADIOIMMUNOLOGY
RADIOISOTOPES
RATS
RODENTS
SOMATOSTATIN
THERAPY
TRACER TECHNIQUES
VERTEBRATES