We have recently reported the presence of immunoreactive (IR) adrenomedullin (ADM) in the human brain. In the present study, the expression of ADM mRNA was studied by Northern blot analysis in the human brain and pituitary, and the presence of IR-ADM in the human pituitary was studied by radioimmunoassay. ADM mRNA was clearly detected in every region of the brain examined and in the pituitary. High concentrations of IR-ADM were present in the whole pituitary (16.7 ± 2.0 pmol/g wet weight, mean ± SEM, n = 4). Reverse phase high performance liquid chromatography of the pituitary showed a peak eluting in the position of human ADM(1-52). These findings suggest that ADM acts as a neuromodulator or a neurotransmitter in the brain, and as an autocrine factor, a paracrine factor, or a neurohormone in the pituitary.
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