Expression of epidermal growth factor in the developing rat kidney

Abstract

Epidermal growth factor (EGF) is important in mammalian renal development. In our study, we investigated the detailed distribution and the time of the first appearance of EGF in developing rat kidney. Kidneys from embryonic 18 (E18)- and 20-day-old (E20) fetuses, postnatal 1 (P1)-, 3 (P3)-, 7 (P7)-, 14 (P14)-, and 21-day-old (P21) pups, and adults were processed for immunohistochemistry and electronmicroscopy. In adult rat kidney, EGF immunoreactivity was found in distal tubule including the thick ascending limb (TAL) and portion 1 of distal convoluted tubule (DCT1), whereas no EGF immunoreactivity was seen in portion 2 of distal convoluted tubule (DCT2) and connecting tubule. In developing kidney, EGF-positive cells first appeared at P3 and were localized in the middle portion of the differentiating TAL of the corticomedullary junction. By P7, the abundance of EGF expression had dramatically increased in the medullary TAL. Between P14 and P21, EGF immunoreactivity was found in the TAL and the DCT for the first time. However, EGF-positive and EGF-negative cells were in the TAL in developing rat kidney. EGF-positive cells did not differ from negative cells in the expression of sodium transport proteins or in the proliferation rate at P3 and P7. In the TAL, smooth-surfaced cells had strong EGF immunoreactivity, but no EGF immunoreactivity was seen in the rough-surfaced cells with well-developed microvilli. Our results suggest that the expression of EGF in developing kidney plays an important role in the regulation of growth and differentiation of the loop of Henle during kidney development and that this may act in the paracrine mode.

Effects of Maternal Renal Dysfunction on Fetal Development

“…Although Toubeau et al (1994) and Jung et al (2005) have observed the immunolocalizations of EGF in distal convoluted tubules and the thick ascending limb of Henle's loop of adult rat kidneys, our results revealed that EGF-positive cells localized to the proximal and the distal tubules in the kidney of immature rats indicating the difference of immunolocalization of EGF in the kidney between adult and immature animals . There are controversial reports on the involvement of EGF on the proliferative activity of the adult kidney.…”

Thick Ascending Limb of the Loop of Henle

“…The relative frequency of the morphologic and functional subtypes in the cortical and medullary TAL suggests that HBC cells correspond to S cells and LBC cells to R cells (3). Molecular characterization of this heterogeneity is still rudimentary; however, R and S cells clearly differ in the expression pattern of EGF (6) and NKCC2 (4). The functional correlates of this heterogeneity are discussed in the following sections.…”

Epidermal growth factors in the kidney and relationship to hypertension

“…Most of the ErbB-family ligands are expressed in the kidney (see Table 2 for some examples), and their expression could be dramatically changed during renal development or in pathological conditions (49,71,130). EGF and its related growth factors are present in the lumen at levels much higher than in plasma.…”