Angiotensin II stimulates proliferation of primary human keratinocytes via a non-AT1, non-AT2 angiotensin receptor

Targeting the renin-angiotensin-aldosterone system in fibrosis

Fibrosis is characterized by excessive deposition of extracellular matrix components such as collagen in tissues or organs. Fibrosis can develop in the heart, kidneys, liver, skin or any other body organ in response to injury or maladaptive reparative processes, reducing overall function and leading eventually to organ failure. A variety of cellular and molecular signaling mechanisms are involved in the pathogenesis of fibrosis. The renin-angiotensin-aldosterone system (RAAS) interacts with the potent Transforming Growth Factor β (TGFβ) pro-fibrotic pathway to mediate fibrosis in many cell and tissue types. RAAS consists of both classical and alternative pathways, which act to potentiate or antagonize fibrotic signaling mechanisms, respectively. This review provides an overview of recent literature describing the roles of RAAS in the pathogenesis of fibrosis, particularly in the liver, heart, kidney and skin, and with a focus on RAAS interactions with TGFβ signaling. Targeting RAAS to combat fibrosis represents a promising therapeutic approach, particularly given the lack of strategies for treating fibrosis as its own entity, thus animal and clinical studies to examine the impact of natural and synthetic substances to alter RAAS signaling as a means to treat fibrosis are reviewed as well.

Plantar Psoriasis Associated with Olmesartan

BACKGROUND

Psoriasis is a chronic inflammatory skin disorder that may be initiated or exacerbated by some drug intakes. Some of the most common medications known to trigger or worsen existing psoriasis include lithium, gold salts, beta blockers and antimalarials.

CONCLUSION

We report an exceptional case of plantar psoriasis in a woman who was treated by olmesartan for 3 years.

Psoriasis during angiotensin receptor blocker exposure: an underestimated adverse drug reaction

BACKGROUND

Angiotensin receptor blockers (ARBs) can induce or exacerbate psoriasis. Psoriasis is unlisted in the Summary of Product Characteristics (SmPC) of ARBs. We aimed to investigate the association between psoriasis and ARB exposure.

METHODS

We reviewed spontaneous reports recorded in the French national Pharmacovigilance Database (FPVD). The association between psoriasis and ARB exposure was assessed using the case/non-case method. We also analyzed literature reports.

RESULTS

We identified 89 reports of psoriasis during ARB exposure in the FPVD. Time to onset was most often less than 1 year. Outcome was favorable in 67% of reports after ARB discontinuation. Almost all ARBs were concerned. The reporting odds ratio (ROR) for psoriasis with this therapeutic class was 4.86 (95%CI 3.92-6.03). In the literature, we found 14 published reports of psoriasis with ARB exposure. Time to onset ranged from 6 weeks to 9 months. Outcome was also favorable after ARB discontinuation in the literature.

CONCLUSIONS

This underestimated adverse drug reaction is a class effect, time to onset is most often less than 1 year and outcome seems favorable after ARB discontinuation. The case/non-case approach highlights a potential safety signal. The SmPC of ARBs should be updated, increased awareness among healthcare professionals is warranted.

Angiotensin II stimulates melanogenesis via the protein kinase C pathway

Melanogenesis is a physiological process that results in the synthesis of melanin pigments, which serve a crucial function in hyperpigmentation. The aim of the present study was to determine the effects of angiotensin II (Ang II) on melanogenesis and to elucidate the molecular events of Ang II-induced melanogenesis. Experiments were performed on human melanocytes to elucidate the pigmenting effect of Ang II and the underlying mechanisms. The elements involved in melanogenesis, including melanin content, tyrosinase (TYR) activity, and microphthalmia-associated transcription factor (MITF) and TYR expression at the mRNA and protein levels were evaluated. Melanin content and TYR activity increased in response to Ang II treatment in a concentration-dependent manner. MITF and TYR mRNA and protein expression levels were increased significantly in response to Ang II in a concentration-dependent manner. The Ang II-induced increase in melanin synthesis was reduced significantly in response to co-treatment with Ro-32-0432, a protein kinase C (PKC) inhibitor, whereas co-treatment with H-89, a PKA inhibitor, did not attenuate the Ang II-induced increase in melanin levels. These results suggest that PKC is required for Ang II-induced pigmentation in human melanocytes and that the mechanism involves the PKC pathway and MITF upregulation.

Psoriasis induced by losartan therapy: a case report and review of the literature

Psoriasis is a papulosquamous disease of multifactorial etiology. A combination of genetic and environmental agents is implicated in its pathogenesis. A variety of triggers, including infection, stress, and medications, have been recognized as precipitants of this disease. Nonsteroidal anti-inflammatory drugs, beta-blockers, lithium, synthetic antimalarials, and gold are the most common drugs implicated in precipitating psoriasis. We report a patient with psoriasis induced by initiation of losartan therapy, which resolved with discontinuation of the drug. The Naranjo adverse drug reaction probability scale score indicated that the association between losartan use and psoriasis was probable.

Evidence of an intracellular angiotensin-generating system and non-AT1, non-AT2 binding site in a human pancreatic cell line

OBJECTIVES

To assess the presence of a local angiotensin-generating systems (LAGS) and its participation in tumor growth in the human pancreatic cancer derived cell line Capan-1.

METHODS

Capan-1 cells were cultured in Dulbecco modified Eagle medium, and angiotensin I was assayed by radioimmunoassay and angiotensin II and vascular endothelial growth factor were assayed by enzyme-linked immunosorbent assay in the supernatant. Immunohistochemistry and reverse transcription-polymerase chain reaction were performed for the expression of AT1 and AT2 receptors. Angiotensin II binding assays and blockade were studied.

RESULTS

High levels of both angiotensins I and II were found in Capan-1 cells, although neither angiotensin I nor angiotensin II was detected in the cell culture supernatant. Reverse transcription-polymerase chain reaction and immunocytochemistry revealed that Capan-1 cells do not express AT1 and AT2 receptors; however, specific binding to the cell membrane was identified for angiotensin II. Neither exogenous angiotensin II nor Dup753 (specific AT1 receptor blocker) affected Capan-1 cells' proliferation or vascular endothelial growth factor secretion.

CONCLUSIONS

Detection of both angiotensin I and angiotensin II along with specific binding of angiotensin II in Capan-1 cells provides evidence of the existence of a LAGS that operates in an intracrine manner. Intracellular angiotensin II may play a role in the aggressiveness of pancreatic cancer and is a possible target for therapeutic agents.

The Role of Neuropeptide Endopeptidases in Cutaneous Immunity

Proteolytic processing and degradation plays an important role in modulating the generation and bioactivity of neuroendocrine peptide mediators, a class of key molecules in cutaneous biology.

Accordingly, the cellular localization and expression, and the molecular biology and structural properties of selected intracellular prohormone convertases and ectopically expressed zinc-binding metalloendoproteases are discussed.

A special reference will be made to the physiologic and pathophysiologic significance of these endopeptidases in cutaneous immunobiology.

Because of the number of pathologically relevant changes in inflammation and tumor progression that can be directly attributed to neprilysin and angiotensin-converting enzyme, a particular focus will be on the role of these enzymes in modulating innate and adaptive immune responses in the skin.

Angiotensin II enhances EGF receptor expression levels via ROS formation in HaCaT cells

BACKGROUND

Recent work has shown a novel function of angiotensin II (Ang II) in skin wound healing in which reactive oxygen species might be involved. As Ang II is known to increase superoxide production by activating NADPH oxidase in some non-phagocytic cells, we hypothesized that the produced superoxide by NADPH activation could contribute to the regulation of epidermal growth factor receptor (EGFR) in keratinocytes.

OBJECTIVE

We examined whether Ang II could generate superoxide and enhance EGFR expression levels in HaCaT cells.

METHODS

Superoxide formation was assessed by using hydroethidine. EGFR expression levels were examined by Western blotting.

RESULTS

Ang II (1-100 microM) increased the superoxide formation. Ang II (1-100 microM) resulted in a dose-dependent increase in cell proliferation in HaCaT cells. Heparin-binding epidermal growth factor activated the EGFR at 5-10 min. Although Ang II did not activate the EGFR, the expression levels of EGFR protein were increased in HaCaT cells treated with Ang II (1 microM) at 6h. Apocynin, a NADPH oxidase inhibitor, decreased the expression levels of EGFR. Xanthine/xanthine oxidase system, an exogenous superoxide generating system, enhanced the EGFR protein expression. Although Ang II did not affect the nitric oxide (NO) production, a NO synthase inhibitor N(omega)-nitro-l-arginine methyl ester suppressed the Ang II-induced EGFR expression levels in HaCaT cells. Thus, constitutive NO is required for the Ang II-induced EGFR expression in HaCaT cells.

CONCLUSION

These results suggest that Ang II enhances the cell proliferation and EGFR expression via superoxide production under the regulation of NO in HaCaT cells, implying that Ang II may regulate the proliferation, differentiation and tumorigenesis of the epidermis by harmonizing the superoxide and NO production.

Physiology of Local Renin-Angiotensin Systems

Since the first identification of renin by Tigerstedt and Bergmann in 1898, the renin-angiotensin system (RAS) has been extensively studied. The current view of the system is characterized by an increased complexity, as evidenced by the discovery of new functional components and pathways of the RAS. In recent years, the pathophysiological implications of the system have been the main focus of attention, and inhibitors of the RAS such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin (ANG) II receptor blockers have become important clinical tools in the treatment of cardiovascular and renal diseases such as hypertension, heart failure, and diabetic nephropathy. Nevertheless, the tissue RAS also plays an important role in mediating diverse physiological functions. These focus not only on the classical actions of ANG on the cardiovascular system, namely, the maintenance of cardiovascular homeostasis, but also on other functions. Recently, the research efforts studying these noncardiovascular effects of the RAS have intensified, and a large body of data are now available to support the existence of numerous organ-based RAS exerting diverse physiological effects. ANG II has direct effects at the cellular level and can influence, for example, cell growth and differentiation, but also may play a role as a mediator of apoptosis. These universal paracrine and autocrine actions may be important in many organ systems and can mediate important physiological stimuli. Transgenic overexpression and knock-out strategies of RAS genes in animals have also shown a central functional role of the RAS in prenatal development. Taken together, these findings may become increasingly important in the study of organ physiology but also for a fresh look at the implications of these findings for organ pathophysiology.

Differential expression of angiotensin receptors in human cutaneous wound healing

BACKGROUND

Angiotensin AT1 and AT2 receptors are expressed in human skin. Furthermore, AT2 receptors have been reported to be upregulated during tissue repair and remodelling in various noncutaneous human tissues.

OBJECTIVES

Detection of alterations in angiotensin II receptor expression during wound healing in human skin.

METHODS

Three models were employed. (i) Primary human keratinocytes were razor scraped in culture flasks and alterations in the expression of angiotensin receptor mRNA determined by semiquantitative reverse transcription-polymerase chain reaction for 1-12 h thereafter. (ii) Early wound healing (48 h after cutting) was studied in punch biopsies from human skin ex vivo by means of immunohistochemical staining using polyclonal antibodies against the AT1 or AT2 receptor. (iii) In vivo wound healing was studied in sections of human cutaneous scars by immunohistochemistry to determine receptor expression early (2 days) and late (2 weeks-3 months) after surgery.

RESULTS

In all experimental settings, an upregulation of both receptor subtypes was noticed after wounding. Immunohistochemically stained skin sections showed a stronger expression of AT2 than of AT1 receptors within the area of scarring. Enhanced receptor expression was detectable as early as 24 h after injury and lasted for up to 3 months.

CONCLUSIONS

From these data, we conclude that angiotensin AT1 and AT2 receptors are upregulated in human cutaneous wounds, giving further support to the concept that angiotensin II plays a role even at an early stage during cutaneous wound healing.

Histological evaluation of the effects of angiotensin peptides on wound repair in diabetic mice

Recent studies have shown that angiotensin peptides accelerate dermal repair. Histological observation of samples taken at the termination of studies showed that the wounds treated with peptides were mature and organized by day 25 after full thickness excision in diabetic mice. However, the mechanisms by which this acceleration occurs has not been determined. In the experiments described here, the effect of angiotensin peptides (AII, A(1-7) and NorLeu (3)-A(1-7) on the quality of the healing wound was evaluated histologically. Administration of the peptides accelerated collagen deposition, re-epithelialization and new blood vessels formation. By day 4, the percentage of the wound with collagen increased two- to six-fold depending upon the peptide. The increase by angiotensin peptides continued throughout the experimental period. On days 4 and 7 9 (only) after injury, exposure to angiotensin peptides increased the number of blood vessels at wound site two-to three-fold. Finally, the percentage of the wound site covered with new epithelium increased after administration of angiotensin peptides. Re-epithelialization was observed as early as day 4 in wounds treated ith angiotensin peptides. The increase was greater at later time points (up to 8-fold ar day 14 with NorLeu(3)-A(1-7) had an increase in neutrophils and macrophages on day 4 after wounding. Overall, administration of these peptides resulted in a healing site that was more mature, including reorganization of the collagen into a basket-weave appearance. Further, these studies confirm the superiority of NorLeu(3)-A(1-7) to AII and A(1-7) in wound healing evaluated at a microscopic level.

Activation of invasiveness of cervical carcinoma cells by angiotensin II

OBJECTIVE

Angiotensin II recently has been reported to promote the growth of several kinds of cells. In this study, we investigated the effect of angiotensin II on cervical carcinoma cells.

STUDY DESIGN

The expression of angiotensin II type I receptor was examined by immunohistochemistry in normal and neoplastic cervical tissues. Invasion assay was examined in Siha cells (cervical squamous cell carcinoma) and vascular endothelial growth factor levels were assayed with a vascular endothelial growth factor enzyme-linked immunosorbent assay kit.

RESULTS

Mean staining intensity level was stronger in invasive carcinoma cells than in normal, dysplasia, and carcinoma in situ tissues. Angiotensin II induced the secretion of vascular endothelial growth factor from Siha cells. Furthermore, angiotensin II promoted the invasive potential of Siha cells. These effects were reversed by the addition of anti-human vascular endothelial growth factor antibody and candesartan (antagonist of angiotensin II type I receptor).

CONCLUSION

Angiotensin II is involved in the progression of cervical carcinoma, because it induces the secretion of vascular endothelial growth factor through angiotensin II type I receptor, which results in the increased invasiveness of carcinoma cells.

[Trigger factors for psoriasis]

Psoriasis is often defined as a disease in which there is a genetic predisposition but environmental stimuli ("trigger factors") are also necessary for clinical expression. Various endogenous and exogenous factors can either induce or exacerbate the clinical features. Knowledge of these factors is of primary importance in clinical practice. This review focuses on the most common environmental trigger factors (infection/superantigens, injury/Köbner phenomenon, stress/neuropeptides, smoking and alcohol) and evaluates the clinical and experimental concepts to explain "environmentally" triggered psoriasis.

Immunohistochemical study of angiotensin receptors in human anagen hair follicles and basal cell carcinoma

BACKGROUND

Angiotensin receptors are the specific receptors of angiotensin II of the renin-angiotensin system. However, expression of the receptors in hair follicles has not been determined.

OBJECTS

To clarify the expression and localization of angiotensin receptors in human anagen hair follicles and basal cell carcinomas.

METHODS

We studied immunohistochemically the expression of angiotensin type 1(AT1) and type 2 (AT2) receptors in human anagen hair follicles and in 16 cases of basal cell carcinoma (BCC) (nine of solid BCC of the circumscribed type, two of adenoid BCC, five of BCC with follicular differentiation).

RESULTS

Our experiments demonstrated the localization of AT1 in the inner root sheath and the inner layers of the outer root sheath. In BCC, positive staining with AT1 was revealed in the tumour cells of basal cell carcinoma with follicular differentiation.

CONCLUSIONS

AT1 may have a role in association with follicular keratinization. Studying AT1 distribution may be useful in understanding the pathophysiology of human hair follicles and the hair follicle-associated tumours.

Immunohistochemical study of angiotensin receptors in normal human sweat glands and eccrine poroma

BACKGROUND

Angiotensin II exerts its actions through its specific receptors. However, expression of these receptors has not been determined in sweat glands.

OBJECTIVES

To clarify the expression and localization of the angiotensin receptors in normal human sweat glands and eccrine poroma.

METHODS

Expression of angiotensin type 1 (AT1) and type 2 (AT2) receptors in normal human eccrine and apocrine sweat glands and 12 cases of eccrine poroma was studied using immunohistochemistry.

RESULTS

In eccrine sweat glands, the acrosyringium and the inner surfaces and luminal cells of the intradermal duct showed positive staining with AT1. In apocrine sweat glands, the intraepithelial duct and luminal cells of the intradermal duct showed positive staining with AT1. In 12 cases of eccrine poroma, some of the tumour cells in the tumour strands and cells surrounding the luminal structures stained positively. There were no positive findings with AT2.

CONCLUSIONS

Studying AT1 distribution may be useful in understanding the pathophysiology of sweat glands and sweat gland tumours.

Differences between squamous cell carcinoma and keratoacanthoma in angiotensin type-1 receptor expression

Angiotensin II receptors are the specific receptors of angiotensin II of the renin-angiotensin system. The existence and role of the receptors in the skin have not been determined. We immunohistochemically studied the expression of angiotensin receptors in the human skin. The results demonstrated the expression of angiotensin type 1 receptor (AT1) in the normal human suprabasal epidermis. The expression pattern suggests the role of AT1 in association with differentiation. In addition, we studied the expression of AT1 in squamous cell carcinoma (SCC) of the skin, SCC of the lip, and keratoacanthoma (KA). Our experiments showed that high, intermediate, and low levels of AT1 were observed in 37 (74.0%), 7 (14.0%), and 2 (4.0%) of 50 cases of SCC of the skin, respectively, and the negative periphery pattern was observed in 17 (77.3%) of 22 cases of KA. These observations suggest that the immunohistochemical study of AT1 is useful to distinguish SCC from KA. Studying the role and distribution of AT1 may help in understanding the pathophysiology of the skin.

Development of angiotensin (1-7) as an agent to accelerate dermal repair

Angiotensin II has been shown to be a potent agent in the acceleration of wound repair. Angiotensin (1-7), a fragment of angiotensin II that is not hypertensive, was found to be comparable to angiotensin II in accelerating dermal healing. This activity was evaluated in four models: rat and diabetic mouse full-thickness excisional wounds; rat random flap; and guinea pig partial thickness thermal injury. In all models, angiotensin (1-7) was comparable to angiotensin II. Angiotensin (1-7) accelerated the closure of wounds in diabetic mice and rats. In diabetic mice the resultant tissue at day 25 after injury was more comparable to normal tissue than the fibrotic scar observed in placebo-treated wounds. In the random flap model, angiotensin (1-7) was comparable to angiotensin II in maintaining flap viability (approximately 82%) and flap survival (40%). Finally, angiotensin (1-7) increased proliferation in the hair follicles at the edge of the wound and site of thermal injury, and the number of patent blood vessels on day 7 after partial thickness thermal injury. These data may be partially explained by the effect of angiotensin II and angiotensin (1-7) on keratinocyte proliferation. While platelet-derived growth factor had no effect on keratinocyte proliferation, angiotensin II and angiotensin (1-7) significantly increased keratinocyte proliferation. These data show that angiotensin(1-7) is comparable to angiotensin II in accelerating skin repair. Furthermore, the hypertensive and wound healing effects can be separated within the family of angiotensin peptides.

Action of angiotensin II on DNA synthesis by human saphenous vein in organ culture

Angiotensin II (Ang II), an effector peptide of the renin-angiotensin system, has been reported to stimulate growth of blood vessels in vivo and smooth muscle cells in culture. In this study, the effect of Ang II on DNA synthesis was examined in deendothelialized human saphenous vein in organ culture. After 7 days' exposure to medium containing 0.4% fetal calf serum plus Ang II, there was a marked increase in DNA synthesis. The effect of Ang II was comparable to the response to platelet-derived growth factor. Responses to Ang II were partially inhibited by the AT(1) receptor antagonist candesartan. An AT(2) receptor antagonist, PD123319, had no effect on Ang II-induced DNA synthesis, either alone or in combination with candesartan. The Ang II peptide analogues [Sar(1), Ile(8)]-Ang II (saralasin) and [Sar(1),Thr(8)]-Ang II (sarthran) acted as agonists, increasing DNA synthesis. In the presence of saralasin, responses to Ang II were inhibited. Tyrphostin-23, a tyrosine kinase inhibitor, prevented Ang II-induced DNA synthesis and reduced DNA synthesis in tissues incubated in medium containing only 0.4% fetal calf serum. In conclusion, Ang II stimulates DNA synthesis in human saphenous vein in organ culture. The effect of Ang II was more marked than has been previously reported in isolated cultured saphenous vein smooth muscle cells, and this effect is mediated in part by an angiotensin type 1 receptor. It is possible that an undefined receptor for Ang II may also be involved in the stimulation of DNA synthesis in this preparation.

The angiotensin type 2 receptor: variations on an enigmatic theme

Since its discovery and molecular characterization, the angiotensin AT2.receptor has been enigmatic with respect to signalling pathways and function. Evidence now emerges that angiotensin II exerts actions through the AT2 receptor which are directly opposed to those mediated by the AT1 receptor. This can be exemplified e.g. by mutually antagonizing effects on cell growth. Upregulated by the endogenous agonist itself, as well as by several growth- and differentiating factors in development and tissue injury, the AT2 receptor appears to act as a modulator of complex biological programmes involved in embryonic development, cell differentiation, tissue protection and regeneration, as well as in programmed cell death. Research on the AT2 receptor has thus unveiled hitherto unknown functions of the renin-angiotensin system extending far beyond the classical role of this old hormonal system in cardiovascular control.

The renin-angiotensin system and its receptors

The renin-angiotensin system (RAS) plays an important role in blood pressure control and in water and salt homeostasis. It is involved in the pathophysiology of hypertension and structural alterations of the vasculature, kidney, and heart, including neointima formation, nephrosclerosis, postinfarction remodeling, and cardiac left ventricular hypertrophy (LVH). Recently, an increased knowledge of the effector peptides of the RAS, their receptors, and their respective functions has led to a new principle of treatment for hypertension: the inhibition of angiotensin (Ang) II via angiotensin-converting enzyme inhibitors or Ang II-receptor antagonists. In this review, the Ang receptors AT1 and AT2 and the potential roles of shorter angiotensin fragments, including Ang III(2-8), Ang IV(3-8), and Ang(1-7), are discussed.

Mast cells and their mediators in cutaneous wound healing--active participants or innocent bystanders?

Mast cells are traditionally viewed as effector cells of immediate type hypersensitivity reactions. There is, however, a growing body of evidence that the cells might play an important role in the maintenance of tissue homeostasis and repair. We here present our own data and those from the literature elucidating the possible role of mast cells during wound healing. Studies on the fate of mast cells in scars of varying ages suggest that these cells degranulate during wounding, with a marked decrease of chymase-positive cells, although the total number of cells does not decrease, based on SCF-receptor staining. Mast cells contain a plethora of preformed mediators like heparin, histamine, tryptase, chymase, VEGF and TNF-alpha which, on release during the initial stages of wound healing, affect bleeding and subsequent coagulation and acute inflammation. Various additional vasoactive and chemotactic, rapidly generated mediators (C3a, C5a, LTB4, LTC4, PAF) will contribute to these processes, whereas mast cell-derived proinflammatory and growth promoting peptide mediators (VEGF, FGF-2, PDGF, TGF-beta, NGF, IL-4, IL-8) contribute to neoangiogenesis, fibrinogenesis or re-epithelization during the repair process. The increasing number of tryptase-positive mast cells in older scars suggest that these cells continue to be exposed to specific chemotactic, growth- and differentiation-promoting factors throughout the process of tissue remodelling. All these data indicate that mast cells contribute in a major way to wound healing. their role as potential initiators of or as contributors to this process, compared to other cell types, will however have to be further elucidated.

Autoradiographic localization and characterization of angiotensin II receptors in the bovine placenta and fetal membranes

Autoradiography and angiotensin (Ang) II receptor binding studies showed that all parts of the bovine placenta and fetal membranes contained high densities of Ang II receptors throughout gestation. The receptors were predominantly subtype 2 (AT2) receptors in the fetal and subtype 1 (AT1) receptors in the maternal compartment. In the allantoamnionic membrane, Ang II receptors were evenly distributed in the mesenchymal tissue, with the highest expression around the few arteries. In the intercotyledonary and cotyledonary allantochorionic membrane, AT2 receptors as well as the less-expressed AT1 receptors were located on mesenchymal cells, especially adjacent to the allantoic endoderm, trophoblast cell layer, and arteries. In the mesenchymal tissue of the placentome, Ang II receptors were mostly expressed at the main branches of the fetal villi of the cotyledons. In the maternal part of the placentome, mainly AT1 receptors but also low densities of AT2 receptors and non-AT1/non-AT2 Ang II binding sites were found close to the stalk and at the main branches of the maternal crypts. Autoradiography revealed no changes in the pattern of distribution of the Ang II receptors throughout gestation. It is suggested that Ang II has an effect on regulatory as well as growth processes in these tissues.