Melanin-concentrating hormone (MCH) is a neuropeptide originally isolated from chum salmon pituitaries. To explore physiological roles of MCH in mammals, we studied the regional distribution of immunoreactive MCH in the rat tissues and the presence of immunoreactive MCH in human adrenal glands, adrenal tumors and plasma by radioimmunoassay, and the expression of MCH mRNA in rat tissues and human brain tissues by Northern blot analysis. Immunoreactive MCH was present in every region of rat brain and neurointermediate lobe of the pituitary gland, with the highest concentrations found in the hypothalamus (48.3 ± 6.6 pmol/g wet weight, mean ± SEM, n = 6). The immunoreactive MCH in rat hypothalamus, frontal lobe, and pons and medulla oblongata was eluted in the position of synthetic human/rat MCH in reverse-phase high-performance liquid chromatography. No immunoreactive MCH was detected in the rat peripheral tissues. Northern blot analysis showed that a single species of MCH mRNA (approximately 1 kb) was expressed specifically in the rat and human hypothalamus, but not detectable in other regions of brain or rat peripheral tissues. Immunoreactive MCH was not detected in human adrenal glands (<0.5 pmol/g wet weight, n = 9) or adrenal tumors including pheochromocytomas. Immunoreactive MCH were not detected in plasma obtained from human healthy subjects (<0.25 pmol/l) and rat (<0.25 pmol/l). These findings indicate that (1) MCH is produced mainly in the hypothalamus and may act as a neurotransmitter, a neuromodulator or a neurohormone in brain and neurointermediate lobe of the pituitary gland, and (2) MCH is not detected in the peripheral blood of human and rat, or in peripheral tissues, suggesting that MCH is not likely to be a circulating hormone in man and rat.
- Melanin-concentrating hormone
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism
- Endocrine and Autonomic Systems
- Cellular and Molecular Neuroscience