AJP - Gastrointestinal and Liver Physiology, Vol 256, Issue 2 436-G441, Copyright © 1989 by American Physiological Society
Atrial natriuretic factor binding sites in the jejunum
C. Bianchi, G. Thibault, A. De Lean, J. Genest and M. Cantin
Laboratory of Pathobiology, Clinical Research Institute of Montreal, Quebec, Canada.
We have studied the localization and the characterization of atrial
natriuretic factor (ANF) binding sites by radioautographic techniques.
Quantitative in vitro radioautography with a computerized microdensitometer
demonstrated the presence of high-affinity, low-capacity 125I-ANF-(99-126)
binding sites (Kd, 48 pM; Bmax, 63 fmol/mg protein) mainly in the villi of
20-microns slide-mounted transverse sections of the rat jejunum.
Competition curves showed 50% inhibitory concentrations of 55 and 1,560 pM
for ANF-(99-126) and ANF-(103-123), respectively. In vivo electron
microscope radioautography showed that 80% of the silver grains were
localized on the lamina propria fibroblast-like cells, 18% on mature
enterocytes, and 2% on capillaries. Bradykinin and adrenocorticotropin did
not compete with ANF binding. These results demonstrate that ANF binding
sites in the rat jejunum possess the pharmacological characteristics of
functional ANF receptors encountered in other rat tissues, and
ultrastructural radioautographs show their cellular distribution. Taken
together, these results demonstrate the presence and the localization of
specific binding sites for ANF in the jejunal villi of the rat small
intestine.
