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Biomedical subjects

J L Renfro

Publications and source records attributed to J L Renfro.

43 records · Page 3Linked to original sources
PubMed1977

Interdependence of Active Na+ and Cl- transport by the isolated urinary bladder of the teleost, Pseudopleuronectes americanus.

The relationship between transepithelial Na+ and Cl- active transport from the mucosal toward the serosal surface was studied by ion substitution experiments in the isolated, perfused urinary bladder of the winter flounder, Pseudopleuronectes americanus. The tissue behaves as a simple ohmic resistance of about 1000 ohm-cm2 which was not significantly changed by perfusion of the lumen (mucosal surface) with Na-free or Cl-free solutions. Trans-epithelial electrical potential difference and short-circuit current were reversed (mucosa positive to negative) by Cl-free perfusion but unaltered by Na-free medium. Short-circuit current did not agree with isotopically measured net Na+ and Cl- flux in either control or ion-substituted medium. Cl-free perfusion depressed net Na+ flux more than 50% and a similar effect was seen on net Cl- flux upon Na-free perfusion. A kinetic analysis of the relationship of Na+ or Cl- flux to the concentration of Na+ or Cl- in the perfusate in the presence and absence of Cl- or Na+, respectively, indicated that Cl-free medium acted as a non-competitive inhibitor of Na+ transport, and the effect of Na-free medium on Cl- transport could be interpreted similarly. This inter-dependence of Na+ and Cl- transport was taken as an indication of co-transport of these two ions. Amiloride (10(-4) M) seemed to inhibit a component of Na flux distinct from the Cl-dependent flux. It had no effect on Cl- transport.

Amiloride↗
PubMed1976

Na-K-ATPase localization in teleost urinary bladder by [3H]ouabain autoradiography.

Previous studies on the urinary bladder of the seawater-acclimated winter flounder (pseudopleuronectes americanus) demonstrated that active Na and Cl transport were ouabain sensitive. This suggested a relationship between the Na pump and Na-K-ATP-ase. The specific binding of [H]ouabain to Na-K-ATPase provides a means of localizing the site of active Na transport. In isolated bladders, a positive linear correlation (r= 0.89) was found between the active Na transport rate and the Na-K-ATPase activity. Ouabain binding by the bladder surface appeared to be saturable and relatively specific, e.g., was reduced by a high K concentration. When only the mucosal side of the bladder was exposed to 5 muM ouabain, both inhibitory effects and binding were small and are explained by finite permeability of the bladder to ouabain. In contrast, binding and inhibitory effects from the serosal side were much greater. Autoradiographs demonstrated that [3H]ouabain was bound only to the serosal side of the epithelial cells. Ultrastructural examination revealed that the area of ouabain binding coincided with the basal and lateral plasma membranes.

Adenosine Triphosphatases↗
PubMed1975

Water and ion transport by the urinary bladder of the teleost Pseudopleuronectes americanus.

Water and ion transport by the isolated teleost urinary bladder were studied. The transepithelial electrical PD across sac-type bladder preparations was unstable, i.e., initially mucosa positive but becoming more negative with time. Perfused bladders maintained a low mucosa positive PD which was stable. Both Na and Cl appeared to be actively transported from mucosal side (M) to serosal side (S). Voltage clamping the bladder at 0, -50, or +50 mV had almost no effect on active or passive Na or Cl flux in either direction. Na and Cl transport seemed electrically neutral. Fluid absorption (M to S) was directly correlated with absorption of osmotically active solutes. These solutes were almost all Na and Cl. The bladder acidified and secreted K+ into the mucosal fluid. Divalent ions were concentrated in the mucosal fluid as a result of fluid absorption. Although furosemide and ethacrynic acid inhibited ion and water transport by the bladder, ouabain was effective at a much lower concentration. Ouabain (10(-4) M) inhibited active Na transport when applied only to the mucosal or only to the serosal surface. Ouabain abolished the PD only from the serosal surface.

Animals↗
PubMed1975

Kidney function of the American eel Anguilla rostrata.

Urine formation in the eel, acclimated to freshwater (FW) and seawater (SW) was studied. SW eels maintained higher plasma and urine osmotic and ionic concentrations than FW eels. Polyethylene-1,2-glycol-14C (PEG-14C) clearance was 29% greater than methoxy-inulin-3H clearance. PEG-14C clearance was considered to be the glomerular filtration rate (GFR). The GFR of SW and FW eels did not differ. Urine flow rate in SW eels was one-third of that in FW eels. The primary urinary solutes in both groups were Na and Cl. Apparently, tubular fluid secretion occurred in FW and, to a lesser degree, in SW eels. With the assumption that water reabsorption was secondary to Na reabsorption in the kidney, the clearance data were used to evaluate all possible explanations for what appeared to be fluid secretion. The data were inconsistent with the possibility that GFR had been underestimated due to glomerular sieving of PEG or active or passive reabsorption of the marker, but consistent with tubular fluid secretion. Furosemide caused diuresis in both groups of eels apparently by inhibition of Na reabsorption in the distal tubule, but it had no effect on the apparent tubular fluid secretion. Tubular ion secretion could not be conclusively implicated as a driving force for fluid secretion. However, the possibility of K, Ca, or Mg secretion in a proximal segment followed by reabsorption in a more distal part of the nephron was not ruled out.

Acclimatization↗