Renal function in response to reduced osmotic load in larval salamanders

Abstract

function in response to reduced osmotic load in larval salamanders. Am. J. Physiol. 226(5) : 1243-l 249. 1974.-Renal function was studied in larval Ambystoma gracile and Dicamptodon ensatus exposed to several osmo-h&ties. Clearance methods were employed in free-swimming larvae using inulin as a GFR marker. GFR, as calculated from the rate of appearance of inulin in the bath, declined from 0.113 to 0.023 ml/10 g-h (A. g racile) and from 0.166 to 0.006 nil/10 g-h (D. ensatus) between 2 mosM (tap water) and 300 mosM (sucrose). In experiments involving urine collection (A. gracile), urine flow. decreased from 0.078 in controls to 0.018 ml/10 g-h in the ZOO-mosM group while GFR decreased from 0.104 to 0.028 ml/l 0 g-h. The latency for the reduction in GFR is about 2 h; however, the return to normal GFR after return to tap water takes about 6 h. Fractional reabsorption of water increased from 25 to 37a/, in the ZOO-mosM group, while fractional reabsorption of Na+, K+, and Cldecreased

SGK1 Regulation of Epithelial Sodium Transport

“…In amphibia and other freshwater or euryhaline vertebrates, the ability of the distal nephron to reabsorb Na + and generate a dilute urine is essential to the adaptation to a decrease in environmental tonicity. Thus, it is physiologically appropriate for Na + transport to increase in distal nephron in response to reduced ECF tonicity (communicated through the basolateral membrane), a response that has been described for A6 cells [38,39], isolated frog skin [40], and other natriferic amphibian tissues [41]. In contrast, the transition to sea water is made possible by NaCl secreting cells in the gill (in teleosts) [42] gland (in elasmobranchs) [43], which are induced by increased tonicity.…”