EGF receptor-binding activity in the urine of normal horses and horses affected by chronic laminitis.
A heterologous radioreceptor binding assay (RRA) has been developed capable of detecting nanogram amounts of epidermal growth factor (EGF) receptor-binding activity in equine urine. The binding parameters of [125I]mEGF (murine EGF) to EGF receptors on equine plasma membranes are in good agreement with values from other EGF-RRA systems. The dissociation constant estimated from equilibrium methods (KD = 4 X 10(-10) M) is in reasonable agreement with that determined from the rate constants (KD = 6 X 10(-10) M) and is in good agreement with values determined in other species. The assay is specific for equine EGF (eEGF) receptor-binding activity and capable of detecting less than 0.34 nM eEGF receptor-binding activity in urine. Equine EGF receptor-binding activity in equine urine form adult horses varied widely between samples (8.5 +/- 6.5 nM). This variability was somewhat reduced when values were adjusted for dilutional effects using urine creatinine as an indicator (3.6 +/- 2.0 nanomoles/g creatinine). No significant differences were demonstrated between the means of EGF binding activity concentrations in clinically normal horses and horses affected by chronic laminitis.
Grosenbaugh
D A
DA
Department of Veterinary Physiology and Pharmacology, College of Veterinary Medicine, Texas A&M University, College Station 77843.
Amoss
M S
MS
Hood
D M
DM
Williams
J D
JD
D000818:Animals; D001667:Binding, Competitive; D002851:Chromatography, High Pressure Liquid; D002908:Chronic Disease; D003404:Creatinine / Q000652:urine; D003429:Cross Reactions; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism / Q000652:urine*; D005534:Foot Diseases / Q000652:urine / Q000662:veterinary; D006724:Hoof and Claw; D006734:Horse Diseases / Q000652:urine*; D006736:Horses; D011237:Predictive Value of Tests; D011869:Radioligand Assay
D004815:Epidermal Growth Factor; D003404:Creatinine; D066246:ErbB Receptors