Visualization of gene expression of short and long forms of prolactin receptor in the rat.

Abstract

PRL receptor gene expression was visualized in various tissues by in situ hybridization, using 35S-labeled probes unique to each form of receptor. Tissues were removed rapidly from adult male and female rats and placed in liquid nitrogen. Cryostat sections (10 microns) were prepared, fixed, pretreated, and dehydrated before incubation with the various probes. Hybridization was performed overnight, after which the slides were first exposed to autoradiographic film and then dipped in nuclear emulsion and exposed for 1-2 weeks. The specificity of the signal was studied by competition and using radiolabeled heterologous probes. Some tissues show no expression of either form of receptor mRNA, such as olfactory bulb and penis. Macroautoradiogram signals (optical density) were compared to a standard curve to observe the variation in mRNA expression, which was expressed in arbitrary units. Sex differences in the expression of PRL receptors were seen in a number of tissues, such as adrenal gland and pituitary. Expression of mRNAs specific to the long form of PRL receptor was predominant in adrenal gland, pituitary, thymus, spleen, skin, heart, and skeletal muscle, whereas the short form was expressed to a greater extent in kidney and lung. At the light microscopic level, the silver grains observed by epipolarization or light field were seen in the specific regions or cells that express PRL receptor mRNAs. In conclusion, the long form transcript predominates in most tissues, except kidney and lung. The advantage of in situ hybridization is that it allows the identification of specific regions or cells expressing mRNAs to be identified. The actions of PRL have not been identified in all tissues expressing PRL receptor transcripts, nor has any definitive correlation been made with the expression of short and long forms of PRL receptor and function.

Control of the Mammary Cell Cycle Clock By Estrogen and Progesterone

“…Wild-type 129SV mammary epithelium adopted the less branched morphology of the endogenous Ragl ~'~ glands following transplant, confirming that systemic effects control this aspect of development, as recently demonstrated (Yant, 1998). Use of in situ hybridization analysis does not reveal expression of the PRLR in the mammary stromal cells of the mouse (Bera, 1994) or the rat (Meister, 1992;Ouhtit, 1993;Shirota, 1995). This suggests that prolactin is unlikely to act via the mammary stroma in rodents.…”

“…Similar defects in ductal branching and end-bud differentiation are also seen in mice lacking prolactin (Horseman, 1997) or Stat5a (Liu, 1998 (Yant, 1998). Use of in situ hybridization analysis does not reveal expression of the PRLR in the mammary stromal cells of the mouse (Bera, 1994) or the rat (Meister, 1992;Ouhtit, 1993;Shirota, 1995). This suggests that prolactin is unlikely to act via the mammary stroma in rodents.…”

Functional Characterization of the Intermediate Isoform of the Human Prolactin Receptor

“…On the other hand, the kidney regulates systemic water electrolyte balance and is known to play a major role in osmoregulation in amphibians and fish (70,71). There is sizable evidence supporting the existence of PRL binding sites in the kidney (72)(73)(74)(75), and PRLr mRNA was found in renal tubules (76,77). Indeed, both PRLr and PRL can be localized on the parietal epithelium of Bowman's capsule (78).…”

Comparative genomics reveals tissue-specific regulation of prolactin receptor gene expression

“…Interestingly, although pE1.3 expression was highest in the renal cortex where proximal tubules are located (Argenzio & Monteiro-Riviere 2001), PRLR-LF in the kidneys of rats is expressed mostly in the inner strip of the outer medulla (Ouhtit et al 1993). This difference may reflect the superior ability of rodents to concentrate urine due to an increased relative length of the renal medulla (Argenzio & Monteiro-Riviere 2001).…”