Electrical potential difference across the cloaca and colon of the australian lizards Amphibolurus ornatus and A. inermis

Morphology and putative function of the colon and cloaca of marine and freshwater snakes

“…Thus, further studies attempting to identify the mechanism of apical Na + transport in these tissues are warranted. It is possible that, like the epithelium of the bladder in mammals (Smith et al,1998) and the hindgut of some lizards (Bentley and Bradshaw,1972), apical Na + transport in the cloacal epithelia of watersnakes is effected by ENaC rather than NKCC. Alternatively, apical Na + transport might be mediated by one of the Na + /H + exchangers, which are known to play a in Na + transport in the kidney of garter snakes (Dantzler et al,1991) and the gastrointestinal tract of mammals (Zachos et al,2005).…”

“…Although modification of the urine has been shown to occur in the coprodeum (Schmidt‐Nielsen and Skadhauge,1967) and urodeum (Kuchel and Franklin,2000) of crocodilians, among lizards retrograde flow of the urine into the colon suggests that the intestinal epithelium may also be an important site of ion and water reclamation (Bentley and Bradshaw,1972; Skadhauge and Duvdevani,1977). Despite differences in habitat use and diet, many reptile species produce cloacal urine (i.e., urine collected after modification) that is low in Na + and high in K + , relative to the ureteral urine (Bentley and Schmidt‐Nielsen,1965; Schmidt‐Nielsen and Skadhauge,1967; Minnich,1970; Robinson and Dunson,1976; Skadhauge and Duvdevani,1977; Taplin,1985).…”

“…Additionally, the relative concentration of these ions is known to vary with dehydration and salt loading in some species (Bradshaw,1972, 1975; Skadhauge and Duvdevani,1977; Bradshaw and Rice,1981; Kuchel and Franklin,1998). The mechanisms by which this variation in ion secretion and water reabsorption might occur have received little attention in reptiles (but see: Bentley and Bradshaw,1972, and references therein).…”

Morphology and putative function of the colon and cloaca of marine and freshwater snakes

“…Thus, further studies attempting to identify the mechanism of apical Na + transport in these tissues are warranted. It is possible that, like the epithelium of the bladder in mammals (Smith et al,1998) and the hindgut of some lizards (Bentley and Bradshaw,1972), apical Na + transport in the cloacal epithelia of watersnakes is effected by ENaC rather than NKCC. Alternatively, apical Na + transport might be mediated by one of the Na + /H + exchangers, which are known to play a in Na + transport in the kidney of garter snakes (Dantzler et al,1991) and the gastrointestinal tract of mammals (Zachos et al,2005).…”

“…Although modification of the urine has been shown to occur in the coprodeum (Schmidt‐Nielsen and Skadhauge,1967) and urodeum (Kuchel and Franklin,2000) of crocodilians, among lizards retrograde flow of the urine into the colon suggests that the intestinal epithelium may also be an important site of ion and water reclamation (Bentley and Bradshaw,1972; Skadhauge and Duvdevani,1977). Despite differences in habitat use and diet, many reptile species produce cloacal urine (i.e., urine collected after modification) that is low in Na + and high in K + , relative to the ureteral urine (Bentley and Schmidt‐Nielsen,1965; Schmidt‐Nielsen and Skadhauge,1967; Minnich,1970; Robinson and Dunson,1976; Skadhauge and Duvdevani,1977; Taplin,1985).…”

“…Additionally, the relative concentration of these ions is known to vary with dehydration and salt loading in some species (Bradshaw,1972, 1975; Skadhauge and Duvdevani,1977; Bradshaw and Rice,1981; Kuchel and Franklin,1998). The mechanisms by which this variation in ion secretion and water reabsorption might occur have received little attention in reptiles (but see: Bentley and Bradshaw,1972, and references therein).…”

Osmoregulation and Excretion

“…The mechanisms involved in the observed water and electrolyte reabsorption from the cloacal‐colonic complex in reptiles are not well understood. A mecholyl‐inhibitable, mucosa‐negative transepithelial potential has been recorded across cloaca‐colon preparations in a number of snakes, lizards, a tortoise and a crocodilian (97, 99, 104, 859, 1620). This observation is compatible with active sodium transport from the lumen side (mucosa) to the blood side (serosa) of these preparations and suggests that transport of water is coupled to sodium transport, as demonstrated by Bindslev and Skadhauge (137) in the large intestine and coprodium of chickens.…”

Morphology and putative function of the colon and cloaca of marine and freshwater snakes

“…Thus, further studies attempting to identify the mechanism of apical Na + transport in these tissues are warranted. It is possible that, like the epithelium of the bladder in mammals (Smith et al,1998) and the hindgut of some lizards (Bentley and Bradshaw,1972), apical Na + transport in the cloacal epithelia of watersnakes is effected by ENaC rather than NKCC. Alternatively, apical Na + transport might be mediated by one of the Na + /H + exchangers, which are known to play a in Na + transport in the kidney of garter snakes (Dantzler et al,1991) and the gastrointestinal tract of mammals (Zachos et al,2005).…”

“…Although modification of the urine has been shown to occur in the coprodeum (Schmidt‐Nielsen and Skadhauge,1967) and urodeum (Kuchel and Franklin,2000) of crocodilians, among lizards retrograde flow of the urine into the colon suggests that the intestinal epithelium may also be an important site of ion and water reclamation (Bentley and Bradshaw,1972; Skadhauge and Duvdevani,1977). Despite differences in habitat use and diet, many reptile species produce cloacal urine (i.e., urine collected after modification) that is low in Na + and high in K + , relative to the ureteral urine (Bentley and Schmidt‐Nielsen,1965; Schmidt‐Nielsen and Skadhauge,1967; Minnich,1970; Robinson and Dunson,1976; Skadhauge and Duvdevani,1977; Taplin,1985).…”

“…Additionally, the relative concentration of these ions is known to vary with dehydration and salt loading in some species (Bradshaw,1972, 1975; Skadhauge and Duvdevani,1977; Bradshaw and Rice,1981; Kuchel and Franklin,1998). The mechanisms by which this variation in ion secretion and water reabsorption might occur have received little attention in reptiles (but see: Bentley and Bradshaw,1972, and references therein).…”

Osmoregulation and Excretion

“…The mechanisms involved in the observed water and electrolyte reabsorption from the cloacal‐colonic complex in reptiles are not well understood. A mecholyl‐inhibitable, mucosa‐negative transepithelial potential has been recorded across cloaca‐colon preparations in a number of snakes, lizards, a tortoise and a crocodilian (97, 99, 104, 859, 1620). This observation is compatible with active sodium transport from the lumen side (mucosa) to the blood side (serosa) of these preparations and suggests that transport of water is coupled to sodium transport, as demonstrated by Bindslev and Skadhauge (137) in the large intestine and coprodium of chickens.…”

Morphology and putative function of the colon and cloaca of marine and freshwater snakes

“…Thus, further studies attempting to identify the mechanism of apical Na + transport in these tissues are warranted. It is possible that, like the epithelium of the bladder in mammals (Smith et al,1998) and the hindgut of some lizards (Bentley and Bradshaw,1972), apical Na + transport in the cloacal epithelia of watersnakes is effected by ENaC rather than NKCC. Alternatively, apical Na + transport might be mediated by one of the Na + /H + exchangers, which are known to play a in Na + transport in the kidney of garter snakes (Dantzler et al,1991) and the gastrointestinal tract of mammals (Zachos et al,2005).…”

“…Although modification of the urine has been shown to occur in the coprodeum (Schmidt‐Nielsen and Skadhauge,1967) and urodeum (Kuchel and Franklin,2000) of crocodilians, among lizards retrograde flow of the urine into the colon suggests that the intestinal epithelium may also be an important site of ion and water reclamation (Bentley and Bradshaw,1972; Skadhauge and Duvdevani,1977). Despite differences in habitat use and diet, many reptile species produce cloacal urine (i.e., urine collected after modification) that is low in Na + and high in K + , relative to the ureteral urine (Bentley and Schmidt‐Nielsen,1965; Schmidt‐Nielsen and Skadhauge,1967; Minnich,1970; Robinson and Dunson,1976; Skadhauge and Duvdevani,1977; Taplin,1985).…”

“…Additionally, the relative concentration of these ions is known to vary with dehydration and salt loading in some species (Bradshaw,1972, 1975; Skadhauge and Duvdevani,1977; Bradshaw and Rice,1981; Kuchel and Franklin,1998). The mechanisms by which this variation in ion secretion and water reabsorption might occur have received little attention in reptiles (but see: Bentley and Bradshaw,1972, and references therein).…”

Osmoregulation and Excretion

“…The mechanisms involved in the observed water and electrolyte reabsorption from the cloacal‐colonic complex in reptiles are not well understood. A mecholyl‐inhibitable, mucosa‐negative transepithelial potential has been recorded across cloaca‐colon preparations in a number of snakes, lizards, a tortoise and a crocodilian (97, 99, 104, 859, 1620). This observation is compatible with active sodium transport from the lumen side (mucosa) to the blood side (serosa) of these preparations and suggests that transport of water is coupled to sodium transport, as demonstrated by Bindslev and Skadhauge (137) in the large intestine and coprodium of chickens.…”