Endothelin-1, a recently isolated peptide, has been observed in different tissues and is involved in several reproductive functions. The objective of the present study was to determine the concentrations of immunoreactive endothelin-1 in the plasma of horses and cattle and in the follicular fluid of horses using a commercial radioimmunoassay kit. Mean immunoreactivity was 47.5%, the minimum detectable dose was 1 pg/tube and the interassay and intra-assay coefficients of variation were 2.36% and 7.26%, respectively. The parallelism between the standard curves and the curves determined with different volumes of plasma and follicular fluid validates the radioimmunoassay of endothelin-1 for these species. To our knowledge, this is the first report in the literature of detection of endothelin-1 in the plasma and follicular fluid of horses and in the plasma of cattle by radioimmunoassay. The present results suggest the use of the radioimmunoassay method employing commercial kits for the determination of endothelin-1 concentrations in horse and cattle plasma and horse follicular fluid because of its high sensitivity, accuracy and reproducibility, in order to study the multiple functions of endothelin-1 in these animals species, and especially in the endocrine-reproductive system.
Endothelins; Radioimmunoassay; Horses; Cattle
