Transforming growth factor-alpha (TGF-alpha) is a polypeptide which is structurally related to epidermal growth factor (EGF) and binds to the EGF receptor. TGF-alpha synthesis occurs in a variety of neoplastic cells and during early fetal development but has not been reported in normal cells of the adult organisms. TGF-alpha has therefore been regarded as an embryonic growth factor which is inappropriately expressed during neoplasia. Here we report that primary cultures of normal human keratinocytes synthesize TGF-alpha. Furthermore, we show that addition of EGF or TGF-alpha to these cultures induces TGF-alpha gene expression, suggesting that a mechanism of auto-induction exists. Analysis of normal skin biopsies using in situ hybridization and immunohistochemistry demonstrates the in vivo presence of TGF-alpha messenger RNA and protein in the stratified epidermis.

The natriuretic peptide receptors are three homologous cell surface proteins, each with a single transmembrane domain. The atrial natriuretic peptide receptor type A (ANPRA) and the homologous receptor type B (ANPRB) are both membrane guanylyl cyclases that synthesize cyclic GMP as an intracellular second messenger. The third receptor in this family, the atrial natriuretic peptide receptor type C (ANPRC), is not coupled to cyclic GMP production. We report on the distribution of the ANPRA, ANPRB, and ANPRC mRNAs in rhesus monkey tissues assayed by in situ hybridization. ANPRA mRNA is most abundantly expressed in the kidney glomerulus, adrenal zona glomerulosa, pituitary, cerebellum, and endocardial endothelial cells of the right and left atrium and right ventricle. In contrast, abundant ANPRB expression appears to be confined to the adrenal medulla, pituitary, and cerebellum. ANPRC mRNA appeared to be expressed very differently than ANPRA and ANPRB. In the heart, ANPRC mRNA is expressed most prominently in endocardial endothelial cells of all four chambers but is also found throughout the myocardium only in the right atrium. These data identify major sites of natriuretic peptide receptor mRNA expression and suggest that there may be prominent cell type-specific differential distribution of these receptors in central and peripheral targets for the natriuretic peptides.Natriuretic peptides are a family of homologous polypeptide hormones that function in both central and peripheral control of fluid volume regulation. As such, these hormones are in dynamic mutual antagonism to the hypertensive renin/angiotensin II/aldosterone system. Of the three known hormones in this family, atrial natriuretic peptide (ANP) (reviewed in reference 13), brain natriuretic peptide (BNP) (37), and type C natriuretic peptide (CNP) (38), ANP has been the most intensely studied, with documented effects on the kidney, adrenals, vasculature, pituitary, and brain. Both ANP and the more recently described BNP are primarily cardiac hormones (26) that are released by the heart in its role as an endocrine organ, regulating fluid and electrolyte homeostasis. A variety of extra-atrial sites of ANP expression have been described (13), suggesting a localized paracrine role for ANP in some tissues. In contrast, the expression of the newly discovered hormone CNP appears to be limited to the nervous system (15).Three members of the natriuretic peptide receptor family have been identified by molecular cloning. The atrial natriuretic peptide receptor type A (ANPRA) (20), also referred to as GC-A (5), is a membrane form of guanylyl cyclase that directly synthesizes the intracellular second messenger cyclic GMP (cGMP) in response to extracellular hormone binding. This receptor responds to stimulation by ANP and BNP (3,5,20,32) but is not a hormonal target for CNP stimulation (1Sa). A second receptor/guanylyl cyclase homologous to ANPRA, referred to as ANPRB (3) for cGMP stimulation (15a). The third receptor in this family, termed ANPRC (10,19), is homolog...

The distribution of transforming growth factor (TGF)-alpha and TGF-beta 1 mRNA containing cells in adult mouse brain was examined using in situ hybridization histochemistry. There were no detectable TGF-beta 1 mRNA-containing cells found in the brain. TGF-alpha mRNA was localized to cell bodies of the caudate nucleus, dentate gyrus, anterior olfactory nuclei, and a laminar distribution of mitral cells in the olfactory bulb. TGF-alpha-synthesizing cells were localized in brain regions that have been shown to synthesize nerve growth factor, epidermal growth factor (EGF) and enkephalins. The function of local synthesis of TGF-alpha in the brain is as yet unknown.

Diazepam binding inhibitor (DBI), an endogenous 10-kDa polypeptide was isolated from rat and human brain by monitoring displacement of radioactive diazepam bound to specific recognition sites in brain synaptic and mitochondrial membranes. The cellular location ofDBI mRNA was studied in rat brain and selected peripheral tissues by in situ hybridization histochemistry with a 35S-labeled singlestranded complementary RNA probe. DBI mRNA was heterogeneously distributed in rat brain, with particularly high levels in the area postrema, the cerebellar cortex, and ependyma ofthe third ventricle. Intermediate levels were found in the olfactory bulb, pontine nuclei, inferior colliculi, arcuate nucleus, and pineal gland. Relatively low but significant levels of silver grains were observed overlying many mesencephalic and telencephalic areas that have previously been shown to contain numerous DBI-immunoreactive neurons and a high

Low-protein feeding results in reduced plasma renin activity (PRA), low prostaglandin production, high intrarenal vascular resistance, and reduced renal plasma flow (RPF) and glomerular filtration rate (GFR) in normal, intact rats. The hemodynamic changes are reversed by converting enzyme inhibitors. In this study, normal rats were fed normal protein (NP) or low protein (LP). PRA was 10.1 +/- 1.3 for NP vs. 5.1 +/- 1.7 ng.ml-1 x h-1 for LP (P < 0.001). Mean arterial pressure fell in both LP and NP during treatment with losartan (DuP-753, a specific angiotensin AT1-receptor inhibitor), but GFR and RPF in LP + losartan became indistinguishable from values obtained in NP and NP + losartan rats. Plasma Na and K and urine excretions of these two electrolytes were unchanged. Angiotensin II (ANG II) binding to isolated glomeruli (n = 19) revealed a dissociation constant of 1.11 +/- 0.22 vs. 1.22 +/- 0.20 nM (not significant) and maximal binding of 763 +/- 89 vs. 432 +/- 75 fmol/mg protein (P < 0.001), indicating an increased number of receptors without changes in affinity in LP. An increased number of receptors in LP compared with NP was also observed by quantitative autoradiography. These results reflect a predominant intrarenal alteration in the response to ANG II in LP. Northern blot and in situ hybridization analysis of the AT1 receptor mRNA showed enhanced gene expression in cortex (glomeruli) and medulla in LP. Dietary protein is an important modulator of the intrarenal actions of ANG II. We show for the first time that protein in the diet modulates the expression of the AT1 receptor gene and that ANG II mediates the hemodynamic changes of LP feeding through the AT1 receptor.