Presence of atrial natriuretic factor prohormone in enterochromaffin cells of the human large intestine

Atrial natriuretic factor is a hormone intimately involved in water
and salt homeostasis. The heart constitutes the major but not
exclusive site of synthesis of this hormone. Among other functions,
the gastrointestinal tract has endocrine functions, plays an
important role in volume regulation of the body, and seems to be a
target organ for atrial natriuretic factor. Therefore, the presence
of atrial natriuretic factor was investigated in the human gut.
Immunoreactive atrial natriuretic factor was found in
intraoperatively obtained samples of normal human colon. Acidic
extracts of human large intestine contained about 0.4 pmol/g wet wt
of atrial natriuretic factor. Analysis of atrial natriuretic factor
immunoreactivity by gel-filtration and reverse-phase
high-performance liquid chromatography showed that about 65% of the
immunoreactivity corresponded to the atrial natriuretic factor
phohormone and about 35% corresponded to the C-terminal ANF99-126.
Immunohistochemistry showed atrial natriuretic factor prohormone
location in enterochromaffin cells of the colon mucosa. Altogether,
these findings show the presence of atrial natriuretic factor
prohormone in enterochromaffin cells of the human large intestine
and may suggest this organ as a site of atrial natriuretic factor
synthesis in humans.