The distributions of three novel
peptides, 7B2,
neuromedin B, and
neuromedin U, in rat, mouse, and human pituitaries, rat hypothalamus, and 30 human
pituitary tumors were investigated with immunocytochemistry. Immunoreactivity for 7B2 was present in rat, mouse, and human gonadotropes, in intermediate lobe cells and posterior lobe nerve fibers in rats and mice, in rat hypothalamus (particularly in the median eminence), and in eight human pituitary gonadotropinomas. In gonadectomized rats, larger, more numerous
LH beta- and 7B2-immunoreactive gonadotropes were seen than in controls. Extractable 7B2-like immunoreactivity was elevated but not significantly so in gonadectomized rat pituitaries [males: castrated, 37.4 +/- 4.3 (mean +/- SE); controls, 26.9 +/- 4.3; females: ovariectomized, 27.2 +/- 2.7; controls, 19.1 +/- 2.2 pmol/gland].
Neuromedin B immunoreactivity was found in normal rat and mouse thyrotropes and weakly in "
thyroidectomy" cells in hypothyroid rats, in which extractable pituitary
neuromedin B was significantly depleted (thyroidectomized, 87.0 +/- 14.0;
methimazole-treated, 82.0 +/- 11.4; control, 230.7 +/- 25.6 fmol/gland).
Hyperthyroid rat pituitaries showed increased
TSH beta and
neuromedin B immunoreactivities and
neuromedin B content (TRH-treated, 385.2 +/- 30.2; T4-treated, 352.6 +/- 20.2; control, 230.7 +/- 25.6 fmol/gland).
Neuromedin U immunoreactivity occurred in corticotropes of all species, in rat and mouse intermediate lobe, and throughout the rat hypothalamus, with immunoreactive cell bodies in the arcuate nucleus.
Neuromedin U-immunoreactive cells were present in six of six human pituitary and five of six human extrapituitary corticotropinomas. In adrenalectomized rats, corticotropes were larger and more numerous than in controls, but extractable anterior pituitary
neuromedin U-like immunoreactivity was not raised (adrenalectomized, 3.30 +/- 0.45; control, 3.32 +/- 0.27 pmol/gland). Our findings suggest that 7B2,
neuromedin B, and
neuromedin U may be involved in pituitary function.