RADIOLIGAND RECEPTOR ASSAY FOR THE DETERMINATION OF LH AND HCG ACTIVITIES UTILIZING RAT OVARIAN RECEPTORS

ABSTRACT A sensitive and specific radioligand receptor assay (RRA) using rat testis homogenate as the receptor source is described for measurement of luteinizing hormone (LH) in bovine blood. Interfering and non-specific substances in blood were removed by means of ion-exchange chromatography on CM-Sephadex C-50. Criteria of validation such as recovery of added LH to plasma or serum, reproducibility, and specificity gave good results. Inhibition curves obtained with bovine plasma and serum were parallel to those obtained with the bovine standard preparation. The range of the dose-response curve was between 0.5–20 ng of bovine LH. The pattern of LH concentrations in purified serum samples under different physiological conditions such as during the oestrous cycle and after administration of GnRH showed a very close correlation whether measured by means of radioimmunoassay (RIA) or receptor assay. Values of RRA-LH were consistently higher than those of RIALH. Thus the lower the RIA-LH levels, the more pronounced were the discrepancies between results of both assay systems. The mean ratio of RRA-LH/RIA-LH for basal levels (less than 1 ng RIA-LH/ml plasma) was 17.8 as compared to a mean ratio for higher peak values (more than 20 ng RIA-LH/ml plasma) of only 1.2.

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APPLICATION OF A RADIOLIGAND RECEPTOR ASSAY FOR THE DETERMINATION OF LUTEINIZING HORMONE IN HUMAN SERUM

Acta Endocrinologica ◽

10.1530/acta.0.080s127 ◽

1975 ◽

Vol 80 (1_Suppla) ◽

pp. S127

Author(s):

F. Leidenberger ◽

R. Willaschek ◽

V. Pahnke

Keyword(s):

Luteinizing Hormone ◽

Human Serum ◽

Receptor Assay ◽

Radioligand Receptor Assay

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Determination of Prolactin in Bovine Blood by Radioligand Receptor Assay and Comparison with Radioimmunological Evaluation

Zentralblatt für Veterinärmedizin Reihe A ◽

10.1111/j.1439-0442.1982.tb01796.x ◽

2010 ◽

Vol 29 (4-5) ◽

pp. 345-352

Author(s):

M. Nawito ◽

D. Schams

Keyword(s):

Bovine Blood ◽

Receptor Assay ◽

Radioligand Receptor Assay

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A comparative study of the action of several lutropin derivatives on rat Leydig cells

Acta Endocrinologica ◽

10.1530/acta.0.0930250 ◽

1980 ◽

Vol 93 (2) ◽

pp. 250-256 ◽

Cited By ~ 6

Author(s):

M. P. de la Llosa-Hermier ◽

C. Tertrin-Clary ◽

M. Evrard-Herouard ◽

Y. Colleaux ◽

C. Hermier ◽

...

Keyword(s):

Leydig Cells ◽

Binding Activity ◽

Camp Accumulation ◽

Lh Receptor ◽

Testosterone Production ◽

Receptor Assay ◽

Testosterone Biosynthesis ◽

Radioligand Receptor Assay ◽

Relative Potencies ◽

Good Agreement

Abstract. Rat intestinal cells prepared from testes were incubated in the presence of different lutropin derivatives obtained by chemical modification of the amino groups. The cAMP accumulation and the testosterone biosynthesis were determined in the cell homogenates. Binding determinations were carried out by a radioligand receptor assay using tritiated methylated lutropin. The binding activities — relative to native LH — of three different derivatives obtained by reductive alkylation (methylated, ethylated and isopropylated LH) were in good agreement with the relative potencies assessed by their capacity to stimulate cAMP and testosterone production. Guanidinated LH (11 — NH2 groups modified) exhibited a binding activity and a relative potency relatively high with regard to cAMP accumulation (as compared with that of native LH). Its steroidogenic potency, however, was very low. When Leydig cells were incubated in the presence of native and guanidinated LH, the testosterone production was similar to that induced by the derivative alone, indicating that the derivative exerted a competitive inhibitory action preventing the stimulation of steroidogenesis by native LH. These results suggest that a guanidinated derivative is able to bind to the LH receptor and the complex so formed is able to be coupled with an adenylate cyclase pool (or cAMP compartment) which is not connected with the steroidogenic pathway.

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Comparison of Microbial Receptor Assay and Liquid Chromatography for Determination of Penicillin G and Amoxicillin in Milk Powder

Journal of AOAC International ◽

10.1093/jaoac/85.3.546 ◽

2002 ◽

Vol 85 (3) ◽

pp. 546-550 ◽

Cited By ~ 1

Author(s):

Kevin L Anderson ◽

Roberta L Lyman ◽

Wlliam A Moats ◽

Arthur P Hansen ◽

John E Rushing

Keyword(s):

Liquid Chromatography ◽

Milk Powder ◽

Penicillin G ◽

Beta Lactam ◽

Receptor Assay ◽

Significant Difference ◽

Dry Milk ◽

Nonfat Dry Milk ◽

Reconstituted Milk

Abstract A microbial receptor assay (Charm II Tablet Beta-Lactam Test) and liquid chromatography (LC) were compared for determination of penicillin G (PG) and amoxicillin (AMOX) in reconstituted milk powder. Nonfat dry milk and whole dry milk were reconstituted (10%, w/v) to concentrations of 0, 2.5, 5, 7.5, and 10 ppb PG; nonfat dry milk was reconstituted (10%, w/v) to 0, 7.5, 10, and 15 ppb AMOX. Reconstituted samples were analyzed blindly by each method. Concentrations determined by both methods demonstrated good agreement. A significant difference between methods (p ≤ 0.05) was observed only for 7.5 ppb PG in defatted dry milk. Significant differences were not observed between known concentrations and concentrations determined by the Charm II assay for PG or AMOX in defatted dry milk and PG in whole dry milk. Results by LC showed significant differences (p ≤ 0.05) between known and measured concentrations at 10 ppb PG in both milks and 0 ppb AMOX in defatted dry milk. These results suggest that both the microbial receptor assay and LC may be useful for determination of PG and AMOX near safe level and tolerance, respectively, in reconstituted milk powder.

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