Role of cutaneous surface fluid in frog osmoregulation

Larsen, Erik Hviid; Ramløv, Hans

doi:10.1016/j.cbpa.2013.04.005

Cited by 23 publications

(15 citation statements)

References 56 publications

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“…This reduction in transporter abundance or activity would lower active sodium uptake rates and contribute to the net increase in sodium loss across the skin. Coincidently, an increase in cutaneous granular secretions to form the mucus layer during sloughing may also contribute to ion loss (Larsen and Ramløv, 2013).…”

Section: Discussionmentioning

confidence: 99%

Living with a leaky skin: upregulation of ion transport proteins during sloughing

Cramp

Franklin

2017

Journal of Experimental Biology

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Amphibian skin is a multifunctional organ providing protection from the external environment and facilitating the physiological exchange of gases, water and salts with the environment. In order to maintain these functions, the outer layer of skin is regularly replaced in a process called sloughing. During sloughing, the outermost layer of the skin is removed in its entirety, which has the potential to interfere with skin permeability and ion transport, disrupting homeostasis. In this study, we measured, in vivo, the effects of sloughing on the cutaneous efflux of ions in toads Rhinella marina kept in freshwater conditions. We also measured transepithelial potential, cutaneous resistance, active ion transport and the distribution, abundance and gene expression of the key ion transport proteins sodium-potassium ATPase (NKA) and epithelial sodium channel (ENaC) during sloughing. We hypothesised that the increase in transepithelial efflux of ions during sloughing is a consequence of increased permeability and/or a reduction in the abundance or expression of cutaneous ion transport proteins, resulting in disruption of internal ion homeostasis. There was a significant increase in sodium and chloride efflux during sloughing in R. marina. However, although in vitro skin resistance decreased after sloughing, active sodium transport increased commensurate with an increase in NKA and ENaC protein abundance in the skin. These changes in skin function associated with sloughing did not affect the maintenance of internal electrolyte homeostasis. These results suggest that during sloughing, amphibians actively maintain internal homeostasis by increasing cutaneous rates of ion uptake.

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Section: Discussionmentioning

confidence: 99%

Living with a leaky skin: upregulation of ion transport proteins during sloughing

Cramp

Franklin

2017

Journal of Experimental Biology

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“…As a consequence of their reliance on terrestrial or aquatic habitats, or a combination thereof, amphibian skin is a sophisticated mucosal organ with specialized adaptations required to perform various critical physiological functions (e.g., ion transport, respiration, water uptake, etc. ), while still maintaining a selective barrier to the external environment (2, 3, 9). Other than the presence of a sophisticated glandular system, a miraculous feature of amphibian skin that sets frogs apart from other vertebrates is their ability to rapidly heal deep wounds which protrude through the dermal layers without scar formation, including complete regeneration of any glands affected by the injury (8).…”

Section: Introductionmentioning

confidence: 99%

Frog Skin Innate Immune Defences: Sensing and Surviving Pathogens

2019

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Amphibian skin is a mucosal surface in direct and continuous contact with a microbially diverse and laden aquatic and/or terrestrial environment. As such, frog skin is an important innate immune organ and first line of defence against pathogens in the environment. Critical to the innate immune functions of frog skin are the maintenance of physical, chemical, cellular, and microbiological barriers and the complex network of interactions that occur across all the barriers. Despite the global decline in amphibian populations, largely as a result of emerging infectious diseases, we understand little regarding the cellular and molecular mechanisms that underlie the innate immune function of amphibian skin and defence against pathogens. In this review, we discuss the structure, cell composition and cellular junctions that contribute to the skin physical barrier, the antimicrobial peptide arsenal that, in part, comprises the chemical barrier, the pattern recognition receptors involved in recognizing pathogens and initiating innate immune responses in the skin, and the contribution of commensal microbes on the skin to pathogen defence. We briefly discuss the influence of environmental abiotic factors (natural and anthropogenic) and pathogens on the immunocompetency of frog skin defences. Although some aspects of frog innate immunity, such as antimicrobial peptides are well-studied; other components and how they contribute to the skin innate immune barrier, are lacking. Elucidating the complex network of interactions occurring at the interface of the frog's external and internal environments will yield insight into the crucial role amphibian skin plays in host defence and the environmental factors leading to compromised barrier integrity, disease, and host mortality.

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“…Amphibians employ a number of strategies to regulate the cutaneous influx/efflux of water. For example, some terrestrial amphibians produce a cutaneous surface fluid (40) or a waxy waterproof secretion (cutaneous layer of lipids) to reduce evaporative water loss (EWL) (44,46). At the cellular level, the movement of ions and water across the skin is tightly regulated.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic basis for loss of water balance in green tree frogs infected with a fungal pathogen

McKercher

Cramp

et al. 2019

American Journal of Physiology-Regulatory, Integrative and Comp

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Chytridiomycosis, a lethal skin disease caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd), disrupts skin function of amphibians, interfering with ionic and osmotic regulation. To regulate fungal loads, amphibians increase their rate of skin sloughing. However, sloughing also causes a temporary loss of ionic and osmotic homeostasis due to disruption of the skin, a key osmoregulatory organ. The combined effects of increased sloughing frequency and chytridiomycosis contribute to the high rates of mortality from Bd infections. However, the mechanisms responsible for the loss of cutaneous osmotic regulation remain unknown. We measured the changes in whole animal water uptake rates, in vitro transcutaneous water fluxes across the ventral skin, and the mRNA expression of epithelial water transport proteins (aquaporins, AQPs) and junctional proteins in Bd-infected and uninfected Litoria caerulea skin. We hypothesize that infected frogs would show reduction/inhibition in cutaneous water transporters responsible for regulating water balance, and sloughing would exacerbate cutaneous water fluxes. We found that infected, nonsloughing frogs had an impaired rate of water uptake and showed increased rates of in vitro water efflux across the ventral skin. In uninfected frogs, the expression of AQPs and junction genes increased significantly with sloughing, which may assist in regulating cutaneous water movements and barrier function in the newly exposed skin. In contrast, infected frogs did not show this postsloughing increase in AQP gene expression. The combination of increased sloughing frequency, impaired water uptake rates, and increased rates of water loss likely contributes to the loss of osmotic homeostasis in frogs infected with Bd.

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Role of cutaneous surface fluid in frog osmoregulation

Cited by 23 publications

References 56 publications

Living with a leaky skin: upregulation of ion transport proteins during sloughing

Living with a leaky skin: upregulation of ion transport proteins during sloughing

Frog Skin Innate Immune Defences: Sensing and Surviving Pathogens

Mechanistic basis for loss of water balance in green tree frogs infected with a fungal pathogen

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