INSULIN-RECEPTORS - THE BINDING-CAPACITY AND LOCALIZATION IN THE DIGESTIVE-TRACT DURING THE RABBITS NEONATAL-PERIOD

The aim of this study was to localize and measure the receptor-binding capacity for insulin in the stomach, duodenum, ileum, jejunum, caecum , colon and in isolated hepatocytes in 48 rabbits aged 1-7, 14 and 21 days. Two methods were employed: radioimmunoassay (RIA) and receptor b inding assay (RBA). Isolated rabbit hepatocytes were used to estimate the maximal binding (B-0). Insulin (INS) concentrations measured by RI A-INS test were highest in the colostrum (701 mu U/mL as 100%) of the does, and in the blood (82 mu U/mL) of newborn rabbits during the firs t day postpartum. The B-0 of colostral insulin for isolated hepatocyte s was 556 mu U/mL, which corresponded to 79.1% of the total binding as assessed by the RIA-INS test. The B-0 for insulin binding in the diff erent parts of the digestive tract tested was the highest on the first day (mean 8.0 fM/g) and the lowest on the 6th day postnatally (mean 4 .9 fM/g; P < 0.01). The receptor capacity for insulin varied in relati on to the different parts of the digestive tract, and with the age of each individual rabbit.