Modulation of intrapituitary CRH gene expression
M. Cassarino1, A. Sesta1, F. Cavagnini1 & F. Pecori Giraldi1,2
Corticotropin-releasing hormone (CRH) is known to be produced and secreted by normal rat corticotropes and to contribute in a paracrine manner to POMC synthesis and ACTH secretion in these cells. The regulation of intrapituitary CRH however still has to be clarified.
Aim: This study was to establish whether CRH gene expression can be measured in rat pituitaries in vitro and whether CRH modulates its own gene expression within the pituitary.
Methods: Rat anterior pituitary primary cultures were incubated with 10 nM CRH and RNA extracted after 24 and 48 h incubation. Control wells were incubated with serum-free DMEM. RNA was reverse-transcribed and subjected to real-time PCR using probes specific to rat CRH and HPRT. Data were analyzed as and are expressed as fold increase over control wells.
Results: Low levels of CRH gene expression were detected in rat pituitary primary cultures. Wells incubated with 10 nM CRH presented increased CRH levels at both 24 h (1.7-fold ±0.4 higher than control wells) and 48 h (2.1-fold ±0.1 higher than control wells).
Conclusions: This study shows that CRH mRNA can be detected at low levels in normal rat pituitary cells, in keeping with its paracrine role. Interestingly, incubation with exogenous CRH induced an up-regulation in CRH gene expression, indicative of a positive intrapituitary feed-back loop. Further studies are needed in order to fully clarify the modulation of locally produced CRH.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.