[The development of immunoreactive corticotropin-releasing factor (IR-CRF) in the hypothalamus, pancreas and gastrointestinal tract of immature rats].

Corticotropin-releasing factor (CRF), a hypothalamic releasing hormone, is now known to be widely distributed in extrahypothalamic tissues such as the pancreas and gastrointestinal tract. There are, however, no data concerning the development of CRF in the gastrointestinal tract in immature animals. Using a specific RIA technique for rat CRF, we have determined the IR-CRF concentrations in acid extracts of hypothalamic, pancreatic and gastrointestinal tissues in immature rats. Gel filtration of the extracts was also undertaken in order to investigate the molecular characteristics of the IR-CRF in the digestive system. Pregnant rats were decapitated at 20 days of gestation and the male fetuses (1 day before birth) were removed by hysterotomy. The male pups were also killed by decapitation immediately after birth and at 1, 3, 7, 14, 21, 28 and 42 days postnatally. The rats older than 3 days were divided into fed and 15-h-fasted groups. Pups were weaned at 21 days. The hypothalamus, pancreas, gastric antrum, duodenum and proxymal jejunum were removed immediately after decapitation. The individual tissue fragments were homogenized in 2N acetic acid and boiled for 5 min. The homogenates were centrifuged at 15,000g at 4 degrees C for 30 min and supernatants were removed, lyophilized and stored frozen until assay. Gel filtration was performed at 4 degrees C on a Sephadex G-50 (fine) column (1.6 X 82 cm). A 3 ml of sample was applied to the column and eluted with 0.2N acetic acid containing 0.25% BSA. Fractions of 3 ml were collected and stored at -20 degrees C until assay. The reagents for RIA were purchased from Peninsula Lab., INC. (Belmont, CA.). 125I-Tyr degrees-rat-CRF was labelled by chloramine-T method. Rabbit anti-CRF serum was used at the final dilution of 1:33,000. The antigen bound antibody was separated from the free antigen by the double antibody method using goat anti-rabbit IgG serum. The sensitivity of this RIA was 2-4 pg/tube. The average coefficients of variation for interassay and intraassay were 11.2% and 9.0%, respectively. Extracts of the pancreas, duodenum and jejunum of immature rats gave dilution curves that were parallel to the rat CRF standard curve as well as that of the hypothalamus.(ABSTRACT TRUNCATED AT 400 WORDS)