Prepro-Orexin and Orexin Receptor mRNAs Are Differentially Expressed in Peripheral Tissues of Male and Female Rats

Abstract

Orexins are produced specifically by neurons located in the lateral hypothalamus. Recent results suggested peripheral actions of orexins. Therefore, we analyzed the mRNA expression of prepro-orexin and the orexin receptor subtypes OX(1) and OX(2) in peripheral rat tissues. Using real-time quantitative RT-PCR we detected significant amounts of prepro-orexin mRNA in testis, but not in ovaries. OX(1) receptor mRNA was highly expressed in the brain and at lower levels in the pituitary gland. Only small amounts of OX(1) receptor mRNA were found in other tissues such as kidney, adrenal, thyroid, testis, ovaries, and jejunum. Very high levels of OX(2) receptor mRNA, 4-fold higher than in brain, were found in adrenal glands of male rats. Low amounts of OX(2) receptor mRNA were present in lung and pituitary. In adrenal glands, OX(2) receptor mRNA was localized in the zona glomerulosa and reticularis by in situ hybridization, indicating a role in adrenal steroid synthesis and/or release. OX(1) receptor mRNA in the pituitary and OX(2) receptor mRNA in the adrenal gland were much higher in male than in female rats. In the hypothalamus, OX(1) receptor mRNA was slightly elevated in female rats. The differential mRNA expression of orexin receptor subtypes in peripheral organs indicates discrete peripheral effects of orexins and the existence of a peripheral orexin system. This is supported by the detection of orexin A in rat plasma. Moreover, the sexually dimorphic expression of OX(1) and OX(2) receptors in the hypothalamus, pituitary, and adrenal glands suggests gender-specific roles of orexins in the control of endocrine functions.

The effect of the estrous cycle on the expression of prepro-orexin gene and protein and the levels of orexin A and B in the porcine pituitary

“…The expression of orexin receptors in the pituitary is also determined by gender, which once again emphasizes the importance of the animals' hormonal status. The expression of the OX1R gene was higher in the pituitary of male rats than in female rats (Jöhren et al, 2001).…”

“…The expression of orexin receptors in the pituitary is also determined by gender, which once again emphasizes the importance of the animals' hormonal status. The expression of the OX1R gene was higher in the pituitary of male rats than in female rats (Jöhren et al, 2001).Research advances over the past decade have confirmed that the orexin system participates in the control of rat and human pituitary. In the existing body of research, there are no studies investigating the presence of orexins in the porcine pituitary and possible impact of hormonal status of the animals connected with the phase of the estrous cycle on orexin concentrations.…”

“…The above results indicate that NP is the main source of orexins in rats, whereas human lactotrophs are the main source of OXA and corticotrophs are the main source of OXB. The presence of OX1R and OX2R was demonstrated in rat (Date et al, 2000;Jöhren et al, 2001Jöhren et al, , 2003, human (Blanco et al, 2001), sheep (Zhang et al, 2005 and porcine pituitaries (Kaminski et al, 2010a). In rats, OX1R and OX2R genes were found in AP and NP.…”

Peripheral tissue–brain interactions in the regulation of food intake

“…Although OX expression in the brain is only located in the LHA-perifornical area (Broberger et al 1998a;Elias et al 1998b;Horvath et al 1999), OX receptors show a widespread distribution in the CNS, with high levels of abundance in some hypothalamic nuclei (ARC, DMH, LHA, PVH and VMH; Marcus et al 2001;Backberg et al 2002). OX receptors are also present in the adrenal gland (López et al 1999), pituitary (Blanco et al 2001 gut (Kirchgessner & Liu, 1999), testis, kidney, ovary and placenta (Johren et al 2001).…”

Expression of Orexin A and Its Receptor 1 in the Vestibular Glands of the Cattle Genital Tract

“…The presence of oxA has been detected in the human placenta which is, however, a transient structure related only to pregnancy (Nakabayashi et al, 2003). Both orexin receptors are expressed in rat ovaries and fluctuate during the estrous cycle (Jöhren et al, 2001;Silveyra et al, 2007). The expression of prepro-orexin and of an orexin receptor sharing close similarities with ox2R has been described in the ovary of a non-mammalian species, the chicken (Ohkubo et al, 2003).…”