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

Mason-Garcia, Meredith; Vaccarella, Myra Y.; Horváth, Judit; Redding, Tommie W.; Groot, Kate; Orsolini, Piero; Schally, Andrew V.

doi:10.1073/pnas.85.15.5688

Cited by 28 publications

(10 citation statements)

References 16 publications

(15 reference statements)

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“…The synthetic SV 1 -hapten was conjugated to fatty acid-free BSA (Sigma) with glutaraldehyde (Sigma) as reported in ref. 30. The SV 1 -hapten-BSA complex was freshly prepared each time.…”

Section: Methodsmentioning

confidence: 99%

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Toller

Horváth

Schally

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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Antagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of various human cancers by multiple mechanisms, which include direct effects on tumor cells through the splice variants (SV) of the GHRH receptor. Our findings suggest that the tumoral protein encoded by SV 1 (SV 1) is a likely functional receptor. The aim of this study was to develop a polyclonal antiserum against a polypeptide analog of segment 1-25 of the putative SV 1 receptor protein. Rabbits were immunized with [Ala-23]SV 1 (1-25)-Tyr-26-Cys-27-NH2 as a hapten, conjugated to BSA or keyhole limpet hemocyanin. The antisera thus generated were evaluated by RIA for binding to the radiolabeled hapten. The specificity and sensitivity of the antisera were studied on xenografts of RL and HT human non-Hodgkin's lymphomas. The sera raised against keyhole limpet hemocyanin-SV 1 hapten, showed binding values of 50 -75% at a 1:56,000 dilution. In Western blot analyses, the purified polyclonal antibody recognized a specific signal with a molecular mass of Ϸ40 kDa in RL and HT lymphomas. This band corresponds to the estimated molecular mass of the GHRH receptor isoform encoded by SV 1. RT-PCR and ligand binding studies also revealed the expression of SV 1 and the presence of high-affinity binding sites for GHRH on RL and HT tumors. Because the antiserum developed recognizes the tumoral GHRH receptor protein encoded by SV 1, it should be of value in various investigations.splice variant ͉ growth hormone-releasing hormone receptor ͉ polyclonal antibody ͉ non-Hodgkin's lymphoma A ntagonists of growth hormone-releasing hormone (GHRH) inhibit the growth of experimental human cancer cell lines xenografted into nude mice or cultured in vitro and are being developed for cancer therapy (1-4). To design still more potent antagonists, we have to fully understand their mechanism of action. GHRH antagonists suppress tumor growth through indirect and direct pathways. The indirect mechanism operates through a suppression of the growth hormone release from the pituitary and the resulting inhibition of the production of insulin-like growth factor I in the liver (1-11). However, the principal action of GHRH antagonists is probably exerted directly on tumors and appears to be mediated by specific receptors for GHRH antagonists on cancer cells (1-9, 11-13). Although the mRNA for GHRH and immunologically active GHRH were demonstrated in various human tumor cells, the mRNA for human pituitary GHRH receptor (GHRH-R) has not been detected on these tumor cells or any of the other cancer models (11,14,15).Because of the structural similarities between GHRH and vasoactive intestinal peptide (VIP), the receptors for VIP could be a target for the GHRH antagonists, but GHRH antagonists inhibit the proliferation of MiaPaCa-2 human pancreatic tumor cells, which do not express the receptors for VIP (13). Moreover, in LNCaP human prostatic carcinoma cells, which are positive for the VIP receptors, GHRH antagonists inhibit tumor growth more powerfully than the antagonists of VIP (1...

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“…The synthetic SV 1 -hapten was conjugated to fatty acid-free BSA (Sigma) with glutaraldehyde (Sigma) as reported in ref. 30. The SV 1 -hapten-BSA complex was freshly prepared each time.…”

Section: Methodsmentioning

confidence: 99%

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Toller

Horváth

Schally

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…However, the duration of release appeared longer with the SB-75 pamoate microgranules. Previously, we showed that the pamoate salt of the somatostatin analog RC-160 in microcapsule formulations exhibited a protracted release as compared with the acetate form (8). Because the primary high release from the microcapsules and/or microgranules ensures a rapid elevated level of antagonist, the initial "burst effect" can be beneficial.…”

Section: Resultsmentioning

confidence: 99%

Prolonged inhibition of luteinizing hormone and testosterone levels in male rats with the luteinizing hormone-releasing hormone antagonist SB-75.

Bokser

Bajusz

Groot

1990

Proc. Natl. Acad. Sci. U.S.A.

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Inhibitory effects of the potent antagonist of luteinizing hormone-releasing hormone N-Ac-[3-(2-naphthyl)-D-alanine',4-chloro-D-phenylalanine2,3-(3-pyridyl)-D-alanine3, D-citrulline6,D-alaninelq]ute'iniing hormone-releasing hormone (SB-75) free of edematogenic effects were investigated in male rats. In a study to determine the effect on luteinizing hormone levels in castrated male rats, SB-75 was injected s.c. in doses of 0.625, 1.25,2.5, 5.0, and 10 pg. Blood samples were taken at different intervals for 48 hr. AU doses of SB-75 significantly decreased luteInzing hormone levels for >6 hr (P < 0.01); this inhibition lasted for >24 hr (P < 0.01) with a dose of5.0 pg and >48 hr with 10 pg (P < 0.05). Serum testosterone levels were also measured in intact male rats u 'ected with SB-75 in doses of 25, 50, and 100 pug. AU doses produced a dramatic fall in testosterone to castration levels 6 hr after injection (P < 0.01); this inhibition of serum testosterone was maintained for >72 hr, but only the 100-pg dose could keep testosterone in the castration range for >24 hr (P < 0.01). In another study using a specific RIA, we obtained the pharmacokinetic release pattern of SB-75 from two sustained delivery formulations of SB-75 pamoate microgranules and examined their effect on serum testosterone. After a single i.m. injection of 20 mg of one batch of microgranules, a large peak corresponding to SB-75 at 45.8 ng/ml was observed, corresponding to the "burst" effect. Levels of the analog decreased to 19.6 ng/ml on day 2, gradually reached a concentration of 4.7 ng/ml on day 7, and kept declining thereafter. Testosterone levels were reduced on day 1 (P < 0.01) and were maintained at low values for >7 days (P < 0.05). In rats injected with 10 mg of SB-75 pamoate microgranules ofthe second batch, SB-75 serum levels rose to 33 ng/ml 3 hr after administration and then fell gradually to =3.4 ng/ml on day 16, but a second small peak was seen on day 28. Subsequently, the analog levels decreased slowly to 2.9 ng/ml on day 42 7100The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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“…13 In addition to the variability within the assay, cross-reactivity existed for peptide structurally similar to RC-160. MasonGarcia et al, 14 for instance, reported 15% cross-reactivity between octreotide and RC-160.…”

Section: Radioimmunoassay Binding Curvementioning

confidence: 99%

In vivo release kinetics of octreotide acetate from experimental polymeric microsphere formulations using oil/water and oil/oil processes

et al. 2004

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The purpose of the present study was to characterize the in vivo release kinetics of octreotide acetate from microsphere formulations designed to minimize peptide acylation and improve drug stability. Microspheres were prepared by a conventional oil/water (o/w) method or an experimental oil/oil (o/o) dispersion technique. The dosage forms were administered subcutaneously to a rat animal model, and serum samples were analyzed by radioimmunoassay over a 2-month period. An averaged kinetic profile from each treatment group, as a result, was treated with fractional differential equations. The results indicated that poly(l-lactide) microspheres prepared by the o/o dispersion technique provided lower area under the curve (AUC) values during the initial diffusion-controlled release phase, 7.79 ng×d/mL, versus 75.8 ng×d/mL for the o/w batch. During the subsequent erosion-controlled release phase, on the other hand, the o/o technique yielded higher AUC values, 123 ng×d/mL, versus 42.2 ng×d/mL for the o/w batch. The differences observed between the 2 techniques were attributed to the site of drug incorporation during the manufacturing process, given that microspheres contain both porous hydrophilic channels and dense hydrophobic matrix regions. An o/o dispersion technique was therefore expected to produce microspheres with lower incorporation in the aqueous channels, which are responsible for diffusion-mediated drug release.

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

Cited by 28 publications

References 16 publications

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Development of a polyclonal antiserum for the detection of the isoforms of the receptors for human growth hormone-releasing hormone on tumors

Prolonged inhibition of luteinizing hormone and testosterone levels in male rats with the luteinizing hormone-releasing hormone antagonist SB-75.

In vivo release kinetics of octreotide acetate from experimental polymeric microsphere formulations using oil/water and oil/oil processes

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