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Different regulation of growth hormone-releasing factor-sensitive adenylate cyclase in the anterior pituitary of young and aged rats.

Abstract：

:Low basal GH secretion and reduced GH responsiveness to different GH secretagogues, including GHRF, have been reported in aged animals and humans. Parallel to the in vivo findings, an impaired GH responsiveness to GHRF is evident in somatotropes from old rats of either sex. We report here that in anterior pituitaries (APs) from aged male and female rats GHRF-induced stimulation of adenylate cyclase (AC) activity was strikingly reduced (male rats, change from baseline 700% in young and 100% in old rats) or lacking (female rats, change from baseline 430% in young and 13% in old rats) when compared to that evoked by GHRF in the APs from young counterparts. Pretreatment with GHRH (5 micrograms/rat iv for 3 days) decreased the high basal AC activity of old male rats [from 33.38 +/- 3.60 to 15.99 +/- 5.75 (SEM) pmol cAMP/min.mg protein], did not alter the GHRF-stimulated rise in AC activity in old male rats, and induced a small but unequivocal rise in AC activity in old female rats (change from baseline 35% vs. 13%, respectively). Pretreatment with GHRF markedly reduced the acute effect of GHRF in the APs from young rats of both sexes (male rats, change from baseline 360% and 700%; female rats, change from baseline 230% and 430% in GHRF-pretreated and control rats, respectively). In parallel studies performed in female rats, it was shown that in vivo pretreatment with GHRF at the same schedule markedly reduced the effect of acute GHRF stimulation on GH secretion from cultured pituitary cells of young rats but left unchanged GHRF-induced stimulation of GH secretion from pituitary cells of old rats. In all, these data suggest that deficiency of endogenous GHRF synthesis and/or release may underlie defective GH secretion in old rats and that a GHRF replacement regimen that reduces the sensitivity of the young somatotrope cells does not alter the sensitivity of (male rats) or exerts a priming effect (female rats) on the old somatotrope cell.

journal_name

Endocrinology

journal_title

Endocrinology

authors

Parenti M,Dall'ara A,Rusconi L,Cocchi D,Müller EE

doi

10.1210/endo-121-5-1649

subject

Has Abstract

pub_date

1987-11-01 00:00:00

pages

1649-53

issue

5

eissn

0013-7227

issn

1945-7170

journal_volume

121

pub_type

杂志文章

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