Radioimmunoassays for fish tail neuropeptides: I. Development of assay and measurement of immunoreactive urotensin I in Catostomus commersoni brain, pituitary, and plasma.

Antisera were raised in rabbits using highly purified urotensin I (UI) or UI (4-41) conjugated with high-molecular-weight proteins. Antiserum 2U4, at a final dilution of 1:300,000, gave 50% binding to iodinated UI (specific activity 40-120 microCi/micrograms). Carp (Cyprinus carpio) and sucker (Catostomus commersoni) UI peptides cross-reacted completely with the antiserum.

Identification of the pituicytes as astroglial cells by indirect immunofluorescence-staining for the glial fibrillary acidic protein.

Glia cells of rat neural lobes (pituicytes) were stained in thin sections (6 micrometers) by the indirect immunofluorescence technique for the glial fibrillary acidic protein (GFA), the S-100 protein and fibronectin. The positive strong GFA-staining of the pituicytes demonstrates their astroglial character. Fibronectin was located along the blood capillaries.