Portland State University. Department of Biology.
Stanley S. Hillman
Date of Publication
Master of Science (M.S.) in Biology
Kidneys, Kidneys Toads -- Physiology
1 online resource (2, vi, 51 p.)
Three aspects of renal function were measured in the toad, Bufo marinus (N=lO): (1) effect of rate of blood volume expansion on renal functions (UFR; GFR; urine and plasma ion concentrations; and ion excretion rates), (2) effect of hypo- and hyperosmotic blood volume expansions on renal functions, and (3) role of GFR and tubular processes in the differential response of UFR under different osmotic expansion stresses. Renal responses to differential rates of blood volume expansion have not been investigated in amphibians. Rate responses will be analyzed considering effects: ( 1) during infusion (neural, or, short term regulation of extracellular fluid volume) and (2) post infusion (hormonal, or, long term regulation of extracellular fluid volume). Volume expansions were administered with hypoosmotic (0.4%) saline and hyperosmotic (1.4%) saline, and ranged in rate from 4.0 to 20.6 ml/kg/min. This protocol is designed to present volume regulatory mechanisms with increased volume stimuli and different osmotic stimuli. Overall, infusion rate had no significant effects on renal responses measured: urine flow rate (UFR); glomerular filtration rate (GFR); urine and plasma ion concentrations; natriuresis; or kaliuresis. This was true for the infusion period and for the observed post infusion period (90 min). Rate was correlated with GFR in the hypoosmotic group (r=0.30, p=0.04) and natriuresis in the hyperosmotic group (r=0.34, p=0.03). A significant positive correlation was observed between UFR and GFR. Relative to treatment, UFR differed significantly; GFR response was inherently similar despite differences at individual intervals, indicating UFR differences between the treatments is due to tubular processes. Responses to hypoosmotic infusion included a significant diuresis, natriuresis, and a decreased urine sodium concentration, relative to hyperosmotic infusion. At low UFRs the hyperosmotic group produced urine relatively concentrated in sodium. Urine sodium concentration and UFR were positively correlated in the hypoosmotic infusion group -- at high UFRs, kidneys were unable to produce a dilute urine.
Bolke, Mark Edward, "Renal Responses to Differential Rates of Blood Volume Expansion in the Toad, Bufo marinus" (1995). Dissertations and Theses. Paper 4973.