Different profiles of isoelectric avian luteinizing hormone components in biological activity and immunoreactivity.

Abstract

Chicken LH components from the glycoprotein fraction of the anterior pituitary glands have been separated to isoelectric homogeneity by means of isoelectric focusing, and investigated for their biological activities in vitro. The activities of these components were measured with LH receptor binding, cyclic AMP accumulation and testosterone production in rat Leydig cells at equal doses expressed as immunoreactivity of IRC-2 (Gunma).All the components were active in the heterologous assay systems, although the relative potency expressed as the ratios of biological activity to immunoreactivity (B: I) differed significantly among the components. Component I, the amount of which is the largest (40-50%), with the most alkaline isoelectricpoint (pI) showed the highest B: I ratio, and the B: I ratio decreased with decreasing pI in the same way as in rat LH components (Wakabayashi, 1980;Hattori et al., 1983). Therefore, pituitary LH from photostimulated male quail, where the relative amount of component I was increased, was estimated to have higher B: I ratios than that from short-day (SD) treated male quail. Furthermore, the differences in activities among the components obtained by the three assays were in the following order: testosterone production>cyclic AMP accumulation>receptor binding, suggesting that the hormonal actions of components with higher B: I ratios (I, II and III) are efficiently amplified in the biological response to the final step. In the incubation of pituitary glands with hypothalamic extracts, component I in the pituitary glands from the long-day (LD) treated group was mostly decreased after the incubation, while all the components were decreased in parallel in the SD-treated group. The results suggest that the LH component releasable to GnRH changes in endocrine status though component I with the highest B: I ratio is relatively releasable in both SD-and LDtreated groups.Pituitary glycoprotein hormones consist of a mixture of several isoelectric components in animal species and man (Braselton and

Effect of cell density on growth hormone release from, cyclic AMP levels in and peptide α-amidation activity of primary cultured rat anterior pituitary cells

“…The cAMP in the supernatants was first succinylated and then measured in duplicate by a double-antibody radioimmunoassay method with a Yamasa cAMP assay kit (Yamasa Shoyu, Choshi, Japan) (Hattori & Wakabayashi, 1983). Antidatimi assays Cultured cells were suspended in 1 ml 0-9% (w/v) NaCl with a rubber scraper at 1-5-24 h of culture, and then centrifuged at 400 g for 5 min at 4°C.…”

An Electrochemical Enzyme Immunoassay for Chicken Luteinizing Hormone: Extension of the Detection Limit by Adequate Control of the Nonspecific Adsorption

“…Isoforms with different isoelectric points and biological activities have been reported (8). A number of chicken (c)LH isoforms which have different in vitro biological activities and immunoactivities in a homologous radioimmunoassay have been recently purified in considerable amounts and partially characterized by the USDA (designated USDA-cLH-K-1 to K-7) (9).…”

The time course and extracellular Ca2+ involvement of growth hormone (GH) releasing factor-induced GH secretion in perifused dispersed rat pituitary cells.

“…Intracellular cAMP was extracted by adding 0.25 ml of 1.5 N perchloric acid and neutralized by KOH. After centrifugation at 1,500 g for 15 min, the supernatants were assayed for cAMP with a radioimmunoassay kit (Yamasa Shoyu Co., Choshi, Japan) (HATTORI and WAKABAYASHI, 1983). …”