Inhibition of rat corticotropin-releasing factor and adrenocorticotropin secretion by an osmotic stimulus.
This study demonstrates that a chronic osmotic stimulus can influence the hypothalamo-pituitary axis by inhibiting the secretion of basal and adrenalectomy-elevated adrenocorticotropin (ACTH) from the anterior pituitary. In rats given 340 mM NaCl instead of tap water to drink for 12 days, plasma concentrations of ACTH decreased to 105 +/- 27 pM (mean +/- S.E.M., n = 6) compared with control animals (182 +/- 13 pM). In adrenalectomised (ADX) rats given 150 mM NaCl to drink for 12 days, plasma ACTH concentrations were greatly increased (783 +/- 141 pM) but in ADX rats treated with 340 mM NaCl for the same period, plasma ACTH was similar to controls (237 +/- 59 pM). The corticotropin-releasing factor (CRF-41) content of the median eminence (ME) was reduced in ADX rats on 150 mM NaCl (854 +/- 78 fmol) and further reduced in ADX rats given 340 mM NaCl (510 +/- 56 fmol) compared with control animals (1239 +/- 114 fmol), suggesting that the decrease in plasma ACTH concentrations in saline-treated animals is secondary to a decrease in the secretion of CRF-41 from the ME. These data are the first evidence for a central mechanism, independent of glucocorticoid feedback, through which a chronic osmotic stimulus can inhibit the activity of CRF-41 neurons.
Jessop
D S
DS
Medical Unit, Westminster Hospital, London, U.K.
Chowdrey
H S
HS
Lightman
S L
SL
D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000378:metabolism*; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D007030:Hypothalamo-Hypophyseal System; D008297:Male; D008473:Median Eminence / Q000187:drug effects / Q000378:metabolism; D009994:Osmolar Concentration; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000494:pharmacology
D001127:Arginine Vasopressin; D012965:Sodium Chloride; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone