Isoelectric focusing and gel filtration studies on the heterogeneity of avian pituitary luteinizing hormone

Abstract

The heterogeneity of avian pituitary LH was shown by means of isoelectric focusing and gel filtration studies coupled with radioimmunoassay. The immunoreactive LH (IR-LH) in anterior pituitary extracts from male quail and chickens contained four components with isoelectric points of 9.8 (component I), 9.4 (component II), 9.0 (component III), and 8.5 (component IV). All IR-LH components possessed the ability to bind to rat ovarian LH receptors but the estimates of potency obtained by the radioreceptor assay did not agree with those from radioimmunoassay. Sephadex G-100 gel filtration of the four individual components obtained from chicken pituitary LH indicated the presence of an LH with a molecular weight of 23,500–25,000 together with a component having double the molecular weight. The components differed in the relative amounts of the larger molecular weight component. The large component was also found in a gel filtration of the extract of chicken anterior pituitary glands. The amounts of the various components were changed in male quail by photostimulation. After 21 days of photostimulation, the amounts of all the components, especially of component I, had increased markedly.