Portal de Periódicos da CAPES

Water balance responses to dehydration and neurohypophysial peptides in the salamander, Notophthalmus viridescens

1977; Elsevier BV; Volume: 31; Issue: 2 Linguagem: Inglês

10.1016/0016-6480(77)90017-x

1095-6840

Patricia Stocking Brown, Stephen C. Brown,

Regulation of Appetite and Obesity

Both terrestrial efts and aquatic newts of Notophthalmus viridescens gain weight rapidly and to the same extent, following dehydration or treatment with neurohypophysial peptides. Newts respond to arginine vasopressin by an increase in water uptake, a decrease in urinary water loss, an increase in bladder resorption and a decrease in glomerular filtration rate. Arginine vasopressin (AVP) doses of 0.4, 4.0, 40.0, and 80.0 mU/g increased body weight in efts at 2 hr by 5.5, 9.4, 14.6 and 15.0%, respectively, but 0.04 mU/g had no effect. In newts, AVP (40 mU/g) increased body weight by 24% in 2 hr, compared to an increase of 11% in response to oxytocin (40 mU/g). Solute loading (1 M NaCl and 2 M sucrose) in newts caused a rapid increase in body weight (16% in the first hour). Urine production was decreased by AVP from 65 to 32 μl/g/hr, and water uptake was increased from 80 to 120 μl/g/hr. The increase in water uptake is assumed to occur across the skin since no drinking could be demonstrated either with phenol red or inulin 14C. Inulin clearance rate (glomerular filtration rate) was decreased from 155 to 89 μl/g/hr by AVP. The water permeability of isolated bladder preparations, but not isolated skin preparations, increased with AVP treatment. Comparison of rehydration rates of urodeles and anurans reveals that N. viridescens can regain its lost water at rates comparable to terrestrial anurans.