Cardiovascular and behavioural changes during water absorption in toads, <i>Bufo alvarius</i> and <i>Bufo marinus</i>

Viborg, A. L.; Wang, Tobias; Hillyard, Stanley D.

doi:10.1242/jeb.02057

Cited by 18 publications

(18 citation statements)

References 30 publications

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“…Cloudsley-Thompson, 1967;Claussen, 1969;Tracy, 1976). Although uncertain, we suspect that some of the physiological parameters affecting skin permeability respond differently to combined changes in temperature and hydration state, possibly involving adjustments in local microcirculatory perfusion of the pelvic patch (Slivkoff and Warburton, 2001;Viborg and Rosenkilde, 2004;Viborg et al, 2006) and constitutive changes in this region's water permeability (Willumsen et al, 2007), mediated by changes in the expression of aquaporins (Hasegawa et al, 2003;Suzuki et al, 2007;Saitoh et al, 2014).…”

Section: Discussionmentioning

confidence: 98%

Temperature and dehydration effects on metabolism, water uptake, and the partitioning between respiratory and cutaneous evaporative water loss in a terrestrial toad

Senzano

Andrade

2018

Journal of Experimental Biology

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Terrestrial anurans often experience fluctuations in body temperature and hydration state, which are known to influence evaporative water loss through the skin (EWL Skin ) and lungs (EWL Resp ). These effects arise from associated changes in skin permeability, metabolism and lung ventilation. Herein, we determined the rates of EWL Skin and EWL Resp in the terrestrial toad Rhinella diptycha at different temperatures and hydration states. We measured oxygen uptake rates to verify whether alterations in the partitioning between EWL Skin and EWL Resp were associated with metabolism-induced changes in pulmonary gas exchange. We also measured the influence of hydration and temperature on water uptake (WU) through the skin. Finally, as estimates of skin resistance to evaporation (R s ) are usually inferred from total evaporative water loss (EWL Total ), under the assumption of negligible EWL Resp , we calculated the potential error in accepting this assumption for different temperature and hydration states. EWL Skin and EWL Resp increased with temperature, but this response was greater for EWL Resp , which was attributed to the temperature-induced elevation in metabolism and lung ventilation. Dehydration caused a decrease in the relative contribution of EWL Skin to EWL Total , mirrored by the concurrent increase in the contribution of EWL Resp , at all temperatures. Thus, R s increased with dehydration. WU rates were dictated by dehydration with little influence of temperature. The partitioning between EWL Skin and EWL Resp was affected by both temperature and hydration state and, under some conditions, considering EWL Resp as negligible led to significant errors in the assessment of skin resistance to evaporation.

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Section: Discussionmentioning

confidence: 98%

Temperature and dehydration effects on metabolism, water uptake, and the partitioning between respiratory and cutaneous evaporative water loss in a terrestrial toad

Senzano

Andrade

2018

Journal of Experimental Biology

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“…7a). Viborg et al. (2006) similarly showed that cutaneous blood flow in hydrated Bufo alvarius could be stimulated to levels comparable to dehydration when toads with an empty bladder were given access to water (Fig.…”

Section: Resultsmentioning

confidence: 79%

“…The degree of stimulation of blood flow is similar to that of mild dehydration. Source: from Viborg et al. (2006).…”

Section: Resultsmentioning

confidence: 99%

Chemosensory function of amphibian skin: integrating epithelial transport, capillary blood flow and behaviour

Hillyard

Willumsen

2010

Acta Physiologica

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Terrestrial anuran amphibians absorb water across specialized regions of skin on the posterioventral region of their bodies. Rapid water absorption is mediated by the insertion of aquaporins into the apical membrane of the outermost cell layer. Water moves out of the epithelium via aquaglyceroporins in the basolateral membrane and into the circulation in conjunction with increased capillary blood flow to the skin and aquaporins in the capillary endothelial cells. These physiological responses are activated by intrinsic stimuli relating to the animals' hydration status and extrinsic stimuli relating to the detection of osmotically available water. The integration of these processes has been studied using behavioural observations in conjunction with neurophysiological recordings and studies of epithelial transport. These studies have identified plasma volume and urinary bladder stores as intrinsic stimuli that activate the formation of angiotensin II (AII) to stimulate water absorption behaviour. The coordinated increase in water permeability and capillary blood flow appears to be mediated primarily by sympathetic stimulation of beta adrenergic receptors, although the neurohypopyseal hormone arginine vasotocin (AVT) may also play a role. Extrinsic stimuli relate primarily to the ionic and osmotic properties of hydration sources. Toads avoid NaCl solutions that have been shown to be harmful in acute exposure, approx. 200-250 mm. The avoidance is partially attenuated by amiloride raising the hypothesis that the mechanism for salt detection by toads resembles that for salt taste in mammals that take in water by mouth. In this model, depolarization of the basolateral membrane of taste cells is coupled to afferent neural stimulation. In toad skin we have identified innervation of skin epithelial cells by branches of spinal nerves and measured neural responses to NaCl solutions that elicit behavioural avoidance. These same concentrations produce depolarization of the basolateral membrane in isolated epithelial preparations. As with salt taste in mammals, the neural responses and depolarization of basolateral membrane potential are partially inhibited by amiloride. In addition, toads are more tolerant of sodium gluconate solution which is consistent with the phenomenon in mammalian taste physiology termed the anion paradox in which sodium salts with larger molecular weight anions produce a reduced intensity of salt taste. Finally, toads also avoid concentrated solutions of a non-electrolyte, mannitol, which differs from NaCl solutions in not affecting transepithelial conductance and requires a longer time to depolarize the basolateral membrane. Osmotic stimuli may mediate sensory processes for longer term detection of conditions with low water potential while ionic stimuli are more important for shorter term analysis of rehydration sources.

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“…Instead, they absorb water across a specialized patch of pelvic skin-the seat patch-and alter circulatory patterns and posture to regulate water uptake (Burggren and Vitalis 2005;Viborg et al 2006).…”

Section: Systems Physiologymentioning

confidence: 99%

Amphibians as Animal Models for Laboratory Research in Physiology

Burggren¹,

Warburton²

2007

ILAR Journal

104

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The concept of animal models is well honored, and amphibians have played a prominent part in the success of using key species to discover new information about all animals. As animal models, amphibians offer several advantages that include a well-understood basic physiology, a taxonomic diversity well suited to comparative studies, tolerance to temperature and oxygen variation, and a greater similarity to humans than many other currently popular animal models. Amphibians now account for approximately 1/4 to 1/3 of lower vertebrate and invertebrate research, and this proportion is especially true in physiological research, as evident from the high profile of amphibians as animal models in Nobel Prize research. Currently, amphibians play prominent roles in research in the physiology of musculoskeletal, cardiovascular, renal, respiratory, reproductive, and sensory systems. Amphibians are also used extensively in physiological studies aimed at generating new insights in evolutionary biology, especially in the investigation of the evolution of air breathing and terrestriality. Environmental physiology also utilizes amphibians, ranging from studies of cryoprotectants for tissue preservation to physiological reactions to hypergravity and space exploration. Amphibians are also playing a key role in studies of environmental endocrine disruptors that are having disproportionately large effects on amphibian populations and where specific species can serve as sentinel species for environmental pollution. Finally, amphibian genera such as Xenopus, a genus relatively well understood metabolically and physiologically, will continue to contribute increasingly in this new era of systems biology and "X-omics."

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Cardiovascular and behavioural changes during water absorption in toads, Bufo alvarius and Bufo marinus

Cited by 18 publications

References 30 publications

Temperature and dehydration effects on metabolism, water uptake, and the partitioning between respiratory and cutaneous evaporative water loss in a terrestrial toad

Temperature and dehydration effects on metabolism, water uptake, and the partitioning between respiratory and cutaneous evaporative water loss in a terrestrial toad

Chemosensory function of amphibian skin: integrating epithelial transport, capillary blood flow and behaviour

Amphibians as Animal Models for Laboratory Research in Physiology

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