Effect of Corticotropin-Releasing Factor on the Release and Synthesis of Prolactin

Abstract

Corticotropin-releasing factor (CRF) has been characterized on the basis of its intrinsic activity to release corticotropin from cultured rat anterior pituitary cells. Injected in intact rats, CRF increases adrenocorticotropic hormone (ACTH) release. Endogenous CRF-like immunoreactivity was detected in the cytoplasm and nucleus of corticotrophs. Using an antirat CRF serum, a similar location of CRF-like immunoreactivity was observed in lactotrophs: cytoplasmic matrix, secretory granules, nucleus and, to a lesser degree, the plasma membrane level were stained. One injection of CRF increased the plasma ACTH concentration 4-fold after 15 min, while plasma prolactin (PRL) increased 2.7-fold 5 min after injection. In vitro, incubation of female pituitary cells with rat CRF (10^–10–10^–8M) had no significant effect on PRL secretion. In contrast, after 4 days of in vitro pretreatment with 17β-estradiol (10^–9M), rat CRF stimulated PRL secretion by 42%. In situ hybridization of whole pituitary slices showed that rat CRF injection significantly increased the labeling of corticotrophs using an ACTH-cDNA probe, but had no significant effect on the labeling of lactotrophs using a PRL riboprobe. These results indicate that CRF is a factor which can modulate PRL release but not the synthesis of PRL.

Characterization of prolactin secretion in gray wolves (Canis lupus)

“…Both during the afternoon PRL surge (Morel et al 1989). Regardless groups maintained a circannual PRL cycle identical to that of of the anesthetic agent used in these experiments, PRL levels did nonpinealectomized wolves (experiment 3b).…”

Acute Increase of GABAergic Neurotransmission Exerts a Stimulatory Effect on GnRH Gene Expression in the Preoptic/Anterior Hypothalamic Area of Ovariectomized, Estrogen- and Progesterone-Treated Adult Female Rats

“…However, it is notewor thy that unlike the releae parameter. GABAergic action on synthesis and mRNA levels has been mostly examined under chronic (>I day) but not acute (<3 h) conditions [30][31][32], The reduced synthesis and mRNA levels could be attributed to the atrophy of cellular activity by nonphysiological high dose for long duration or a secondary effect of blocking the secretion. In the present study.…”

Circadian Patterns of Plasma Immunoreactive Corticotropin, Beta-Endorphin, Corticosterone and Prolactin after Immunoneutralization of Corticotropin-Releasing Hormone

“…data]. Interestingly, recent stud ies suggested that CRH may also be an important stimulus of prolactin secretion [ 12]. Since the role of CRH in the circadian patterns of |3-END and PRL has not been studied, and since the suppression of cortisol by dexamethasone (DEX) is a widely used clinical test in Cushing's syndrome and in neuropsychiatric disorders [13.…”

“…PRL levels are highly responsive to environmental stimuli and various stressors [33], PRL responses to stress are increased after adrenalectomy [34, 35] and glucocorticoids suppress PRL secretion [33]. Recently, CRH-like immunoreactivity was de tected in lactotrophs and increase of PRL release was found after injection of CRH in vivo, suggesting a role of CRH in PRL secretion, under certain physiological conditions [12]. We stud ied the effects of immunoneutralization of CRH on plasma PRL levels during the CRH-mediated diurnal surge.…”