Search PubMed⌕ Search

Biomedical subjects

R K Webb

Publications and source records attributed to R K Webb.

59 records · Page 4Linked to original sources
PubMed1977

Relationship between phosphaluria and acute hypercapnia in the rat.

Standard clearance studies were performed in mechanically ventilated intact and acutely thyroparathyroidectomized (TPTX) rats to document and characterize the effect of hypercapnia (HC) on urinary phosphorus excretion (U(P)V). HC as compared to normocapnia (NC) was associated with an increase in U(P)V in intact (62.5 vs. 7.93 mug/min) and TPTX (30.5 vs. 0.59 mug/min) rats, an increase in filtered load of phosphorus in intact (218 vs. 191 mug/min) and TPTX (243 vs. 146 mug/min) rats, an increase in blood bicarbonate concentration in intact (27.8 vs. 26.0 meq/liter) and TPTX (24.5 vs. 22.3 meq/liter) animals, and a decrease in blood pH in intact (7.15 vs. 7.42) and TPTX (7.07 vs. 7.39) rats. Additional TPTX rats with NC and HC were studied during phosphorus infusion at a comparable filtered load of phosphorus (NC = 307 mug/min and HC = 328 mug/min). U(P)V was 18.5 mug/min in NC and 85.2 mug/min in HC animals. Intact NC animals infused with NaHCO(3) achieved a blood bicarbonate of 45.9 meq/liter compared to 26.0 meq/liter in intact NC NaCl-infused rats. U(P)V was 10.0 mug/min in the NaHCO(3) and 7.93 mug/min in NaCl-infused animals. In intact HC animals infused with NaHCO(3), blood pH was 7.36 compared to 7.42 in NC intact NaCl-infused animals. U(P)V was 83.2 mug/min in the HC bicarbonate-infused and 7.93 mug/min in the NC NaCl-infused rats. These experiments demonstrate that elevated blood carbon dioxide tension per se increases U(P)V. Increases in filtered load of phosphorus and blood bicarbonate which are associated with HC contribute to the phosphaturia as does parathyroid hormone. The phosphaturia is not dependent upon reduction of extracellular pH.

Acidosis↗
PubMed1975

Acute effects of lithium on the renal concentrating mechanism in a primate.

Although chronic lithium therapy has been associated with a defect in the urinary concentrating mechanism, short-term renal effects of lithium have received little attention in the intact animal. Solute-free water reabsorption (T-cH2O) and free water clearance (CH2O) were measured in primates of the genus Galago under control conditions and while animals were receiving either 0.5 mmol/kg-h or 1.0 mmol/kg-h lithium chloride (135 mM) intravenously. CH2O was unchanged by lithium infusion (P greater than 0.10), whereas T-cH2O was significantly depressed at all levels of osmolal clearance (P smaller than 0.01). Spontaneous recovery of near-normal T-cH2O was documented in two animals within 1 wk following acute lithium infusion. In addition it was observed that lithium-induced depression of T-cH2O could be partially prevented by pretreatment with intravenous amiloride. These results suggest that alterations in the renal concentrating mechanism can occur rapidly following the onset of lithium administration. They also imply that impairment of the renal concentrating mechanism by lithium is due at least in part to antagonism of the action of vasopressin on the collecting duct.

Amiloride↗