Disproportionate accumulation of immunoreactive corticotropin, melanotropin, and lipotropin in the brain of the maturing rat

A. Barnea, G. Cho, J. C. Porter

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Abstract

The accumulation of immunoreactive ACTH (ACTH(i)), αMSH (αMSH(i)), and γ-lipotropin (γLPH(i)) as a function of age (10-120 days) was determined in three regions of the brain of male rats: the medial basal hypothalamus (MBH), the preoptic anterior hypothalamus (POA), and the thalamus. In each region of the brain, the concentrations of ACTH(i), αMSH(i), and γLPH(i) increased with age. In the MBH, the increase occurred in such a manner that the molar ratio of αMSH(i) to ACTH(i) remained constant regardless of the age of the animals. In contrast, in the POA and thalamus, the increase occurred disproportionately in favor of αMSH(i), and thus the molar ratio of αMSH(i) to ACTH(i) was 3 times higher in the adult (120 days old) than in the young (10 or 21 days old) animals. Nevertheless the ratio of (ACTH(i) plus αMSH(i)) to γLPH(i) was constant at a level of about 2 regardless of the age of the animal or the region of the brain. Extracts of the MBH or POA were fractionated on columns of Sephadex G-75 superfine. The gel filtration profiles of ACTH(i) were indicative of the presence of five molecular weight forms of ACTH: greater than 40K, 30-40K, 20-30K, 5.7K, and 4.5K. We tentatively identified greater than 40K ACTH as a large form of proopiocortin, 20-30K ACTH as ACTH biosynthetic intermediate, 5.7K as glycosylated ACTH(1-39), and 4.5K ACTH as ACTH-(1-39). Regardless of the age of the animals, the fractional amount of 30-40K ACTH was high in the MBH compared to that in the POA. Moreover, the small fractional amount of 30-40K ACTH in the POA was associated with a large fractional amount of small molecular weight forms of ACTH(i). However, the predominant form of ACTH(i) in the POA changed with age: 20-30K ACTH was the major form in the young, whereas 4.5K ACTH was the major form in the adult. These results support the proposal that the production of proopiocortin increases with age, and there is enhanced processing of proopiocortin to ACTH-(1-39) and αMSH in the brain of the maturing rat.

Original languageEnglish (US)
Pages (from-to)1990-1998
Number of pages9
JournalEndocrinology
Volume109
Issue number6
StatePublished - 1981

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beta-Lipotropin
Melanocyte-Stimulating Hormones
Adrenocorticotropic Hormone
Brain
Anterior Hypothalamus
Middle Hypothalamus
Pro-Opiomelanocortin

ASJC Scopus subject areas

  • Endocrinology
  • Endocrinology, Diabetes and Metabolism

Cite this

Disproportionate accumulation of immunoreactive corticotropin, melanotropin, and lipotropin in the brain of the maturing rat. / Barnea, A.; Cho, G.; Porter, J. C.

In: Endocrinology, Vol. 109, No. 6, 1981, p. 1990-1998.

Research output: Contribution to journalArticle

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abstract = "The accumulation of immunoreactive ACTH (ACTH(i)), αMSH (αMSH(i)), and γ-lipotropin (γLPH(i)) as a function of age (10-120 days) was determined in three regions of the brain of male rats: the medial basal hypothalamus (MBH), the preoptic anterior hypothalamus (POA), and the thalamus. In each region of the brain, the concentrations of ACTH(i), αMSH(i), and γLPH(i) increased with age. In the MBH, the increase occurred in such a manner that the molar ratio of αMSH(i) to ACTH(i) remained constant regardless of the age of the animals. In contrast, in the POA and thalamus, the increase occurred disproportionately in favor of αMSH(i), and thus the molar ratio of αMSH(i) to ACTH(i) was 3 times higher in the adult (120 days old) than in the young (10 or 21 days old) animals. Nevertheless the ratio of (ACTH(i) plus αMSH(i)) to γLPH(i) was constant at a level of about 2 regardless of the age of the animal or the region of the brain. Extracts of the MBH or POA were fractionated on columns of Sephadex G-75 superfine. The gel filtration profiles of ACTH(i) were indicative of the presence of five molecular weight forms of ACTH: greater than 40K, 30-40K, 20-30K, 5.7K, and 4.5K. We tentatively identified greater than 40K ACTH as a large form of proopiocortin, 20-30K ACTH as ACTH biosynthetic intermediate, 5.7K as glycosylated ACTH(1-39), and 4.5K ACTH as ACTH-(1-39). Regardless of the age of the animals, the fractional amount of 30-40K ACTH was high in the MBH compared to that in the POA. Moreover, the small fractional amount of 30-40K ACTH in the POA was associated with a large fractional amount of small molecular weight forms of ACTH(i). However, the predominant form of ACTH(i) in the POA changed with age: 20-30K ACTH was the major form in the young, whereas 4.5K ACTH was the major form in the adult. These results support the proposal that the production of proopiocortin increases with age, and there is enhanced processing of proopiocortin to ACTH-(1-39) and αMSH in the brain of the maturing rat.",
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N2 - The accumulation of immunoreactive ACTH (ACTH(i)), αMSH (αMSH(i)), and γ-lipotropin (γLPH(i)) as a function of age (10-120 days) was determined in three regions of the brain of male rats: the medial basal hypothalamus (MBH), the preoptic anterior hypothalamus (POA), and the thalamus. In each region of the brain, the concentrations of ACTH(i), αMSH(i), and γLPH(i) increased with age. In the MBH, the increase occurred in such a manner that the molar ratio of αMSH(i) to ACTH(i) remained constant regardless of the age of the animals. In contrast, in the POA and thalamus, the increase occurred disproportionately in favor of αMSH(i), and thus the molar ratio of αMSH(i) to ACTH(i) was 3 times higher in the adult (120 days old) than in the young (10 or 21 days old) animals. Nevertheless the ratio of (ACTH(i) plus αMSH(i)) to γLPH(i) was constant at a level of about 2 regardless of the age of the animal or the region of the brain. Extracts of the MBH or POA were fractionated on columns of Sephadex G-75 superfine. The gel filtration profiles of ACTH(i) were indicative of the presence of five molecular weight forms of ACTH: greater than 40K, 30-40K, 20-30K, 5.7K, and 4.5K. We tentatively identified greater than 40K ACTH as a large form of proopiocortin, 20-30K ACTH as ACTH biosynthetic intermediate, 5.7K as glycosylated ACTH(1-39), and 4.5K ACTH as ACTH-(1-39). Regardless of the age of the animals, the fractional amount of 30-40K ACTH was high in the MBH compared to that in the POA. Moreover, the small fractional amount of 30-40K ACTH in the POA was associated with a large fractional amount of small molecular weight forms of ACTH(i). However, the predominant form of ACTH(i) in the POA changed with age: 20-30K ACTH was the major form in the young, whereas 4.5K ACTH was the major form in the adult. These results support the proposal that the production of proopiocortin increases with age, and there is enhanced processing of proopiocortin to ACTH-(1-39) and αMSH in the brain of the maturing rat.

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