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Lack of Correlation Between Immunoreactive Corticotropin‐Releasing Factor Concentration Profiles in Hypophysial‐Portal and Peripheral Plasma
Author(s) -
Plotsky Paul M.,
Otto Stefan,
Toyama Terry,
Sutton Steve
Publication year - 1990
Publication title -
journal of neuroendocrinology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.062
H-Index - 116
eISSN - 1365-2826
pISSN - 0953-8194
DOI - 10.1111/j.1365-2826.1990.tb00394.x
Subject(s) - medicine , endocrinology , median eminence , peripheral , portal circulation , secretion , adrenalectomy , hypothalamus , corticotropin releasing hormone , chemistry
Corticotropin‐releasing factor (CRF‐41) is the primary mediator of adrenocorticotropin secretion from the adenohypophysis. This 41‐amino‐acid peptide is synthesized in perikarya of the paraventricular nuclei, transported to nerve terminals in the external zone of the median eminence and released into the hypophysial‐portal circulation. It is also synthesized in multiple extrahypothalamic and peripheral sites. In addition, immunoreactive (ir) CRF‐41 is present in the systemic circulation, raising the possibility that systemic measurements might provide a useful index of hypothalamic irCRF‐41 secretion. This hypothesis was tested in several rat models. Neither bilateral destruction of hypothalamic irCRF‐41 producing perikarya, nor infundibular stalk transection altered peripheral plasma irCRF‐41 concentration. Furthermore, central administration of norepinephrine, an agent previously shown to evoke irCRF‐41 secretion into the portal circulation, was without effect on peripheral irCRF‐41 concentration. Finally, while increased irCRF‐41 levels in both the hypophysial‐portal and the peripheral circulation were associated with nitroprusside‐induced hypotension, bilateral paraventricular nuclei lesions blocked irCRF‐41 secretion into the hypophysial‐portal circulation without blunting the rise observed in the peripheral circulation. The source of peripheral irCRF‐41 remains undetermined; however, the adrenals may be excluded as bilateral adrenalectomy failed to alter circulating irCRF‐41 levels. Therefore, our observations do not support the concept that peripheral irCRF‐41 levels provide a useful index of hypothalamic secretion of this peptide into the hypophysial‐portal circulation under the conditions tested.