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K J Karnaky

Publications and source records attributed to K J Karnaky.

At least 37 records · Page 2Linked to original sources
PubMed1979

Elasmobranch rectal gland cell: autoradiographic localization of [3H]ouabain-sensitive Na, K-ATPase in rectal gland of dogfish, Squalus acanthias.

Specific binding of radiolabeled inhibitor was employed to localize the Na-pump sites (Na,K-ATPase) in rectal gland epithelium, a NaCl-secreting osmoregulatory tissue which is particularly rich in pump sites. Slices of gland tissue from spiny dogfish were incubated in suitable [3H]ouabain-containing media and then prepared for Na,K-ATPase assay, measurement of radiolabel binding, or quantitative freeze-dry autoradiography at the light microscope level. Gross freezing or drying artifacts were excluded by comparison with additional aldehyde-fixed slices. Characterization experiments demonstrated high-affinity binding which correlated with Na,K-ATPase inhibition and half-saturated at approximately 5 microM [3H]ouabain. At this concentration, the normal half-loading time was approximately 1 h and low-affinity binding to nonspecific sites was negligible. Autoradiographs from both 1- and 4-h incubated slices showed approximately 85% of the bound [3H]ouabain to be localized within a 1-micrometer wide boundary region where the highly infolded basal-lateral cell membrane are closest to the mitochondria. These results establish that most of the enormous Na,K-ATPase activity associated with rectal gland epithelium is in the basal-lateral cell membrane facing interstitial fluid and not in the luminal membrane facing secreted fluid. Moreover, distribution along the basal-lateral membrane appears to be nonuniform with a higher density of enzyme sites close to mitochondria.

Animals↗
PubMed1979

George Dock, MD.

Explore the source record for details and available documents.

History, 19th Century↗
PubMed1978

Ion transport across the isolated intestinal mucosa of the winter flounder, Pseudopleuronectes americanus. I. Functional and structural properties of cellular and paracellular pathways for Na and Cl.

The isolated intestinal mucosa of the flounder, Pseudopleuronectes americanus, when bathed in a 20 mM HCO3-Ringer's solution bubbled with 1% CO2 in O2, generated a serosa-negative PD and, when short-circuited, absorbed Cl at almost 3 times the rate of Na. Reducing HCO3 to 5 mM decreased the net Cl flux by more than 60%. The following results suggest that, despite the PD, Na and Cl transport processes are nonelectrically coupled: replacing all Na with choline abolished both the PD and net Cl flux; replacing all Cl with SO4 and mannitol abolished the PD and the net Na flux; and adding ouabain (to 0.5 mM) abolished the PD and the net Cl flux. Nearly all of the unidirectional serosa-to-mucosa Cl flux (JClsm) seemed to be paracellular since it varied with PD and Cl concentration in a manner consistent with simple diffusion. JClsm was only about one-fourth of JNasm, suggesting that the paracellular pathway is highly cation-selective. The data can be explained by the following model: (i) Na and Cl uptake across the brush border are coupled 1 : 1; Na is pumped into the lateral space and Cl follows passively, elevating the salt concentration there; (ii) the tight junction is permeable to Na but relatively impermeable to Cl; and (iii) resistance to Na diffusion is greater in the lateral space (considered in its entirety) than in the tight junction. If these assumptions are correct, the serosa-negative transmural PD is due mainly to a salt diffusion potential across the tight junction and, under short-circuit condition, most of the Na pumped into the lateral space diffuses back into the luminal solution, whereas most of the Cl enters the serosal solution. Morphological features of the epithelium support this interpretation: the cells are unusually long (60 micrometer); there is little distension of the apical 12 micrometer of the lateral space during active fluid absorption; and distension distal to this region is intermittently constricted by desmosomes.

Animals↗
PubMed1977

Chloride transport across isolated opercular epithelium of killifish: a membrane rich in chloride cells.

The opercular epithelium of Fundulus heteroclitus contains typical gill chloride-secreting cells at the high density of 4 X 10(5) cells per square centimeter. When isolated, mounted as a membrane, and short-circuited, it actively transports chloride ions from the blood side to the seawater side of the preparation. This preparation offers a useful approach to the study of osmoregulation in bony fishes.

Animals↗
PubMed1977

Active chloride transport in the in vitro opercular skin of a teleost (Fundulus heteroclitus), a gill-like epithelium rich in chloride cells.

1. The opercular epithelium lining the inside of the gill chamber of the killifish, Fundulus heteroclitus, contains Cl(-) cells, identical in fine structure to gill Cl(-) cells, at the high density of 4 x 10(5) cells/cm(2). This epithelium can be isolated, mounted in a Lucite chamber, and its ion transport properties studied with the short-circuit current technique.2. The isolated opercular epithelia of seawater-adapted fish, when bathed on both sides with Ringer and gassed with 100% O(2), displayed a mean short-circuit current of 136.5 +/- 11.1 muA/cm(2), a mean transepithelial potential difference of 18.7 +/- 1.2 mV (blood side positive), and a mean transepithelial d.c. resistance of 173.7 +/- 12.1 Omega.cm(2) (mean +/- S.E. of mean; n = 64).3. The transepithelial potential difference across the opercular epithelia of seawater-adapted fish was dependent on both Na(+) and Cl(-) in the bathing solutions and increased linearly with increasing Cl(-) concentrations with a slope of 28.3 +/- 2.1 mV/tenfold concentration change. The short-circuit current was Na(+) dependent and increased linearly with increasing Cl(-) concentrations with no evidence of saturation kinetics below 142.5 m-equiv/l.4. When the short-circuited epithelia of seawater-adapted fish, bathed on both sides with Ringer, was gassed with 100% O(2) the mean Cl(-) blood side to seawater side flux was 211.7 +/- 27.1 muA/cm(2) and the mean Cl(-) seawater side to blood side flux was 48.9 +/- 10.0 muA/cm(2). This resulted in a net Cl(-) blood side to seawater side flux of 162.8 muA/cm(2) which was not statistically different (P > 0.70) from the mean short-circuit current of 158.6 +/- 16.3 muA/cm(2) for these flux studies. The mean Na(+) blood side to seawater side flux was 32.2 +/- 3.3 muA/cm(2) and the mean Na(+) seawater side to blood side flux was 34.8 +/- 4.1 muA/cm(2), resulting in no significant (P > 0.20) net flux of this cation. Similar results were obtained with short-circuited epithelia of seawater-adapted fish when bathed on both sides with Ringer and gassed with 95% O(2)/5% CO(2).5. Ouabain (10(-5)M), furosemide (10(-3)M), thiocyanate (10(-2)M), adrenaline (10(-6)M), and anoxia (100% N(2)) decreased the short-circuit current 92.7, 85.0, 45.3, 62.6, and 83.3% respectively. Theophylline (10(-4)M) stimulated the short-circuit current 54.9%. Increasing the HCO(3) (-) concentration in the bathing solutions had a stimulatory effect on the short-circuit current and the potential difference across epithelia from seawater-adapted fish.6. The opercular epithelia of freshwater-adapted F. heteroclitus, when bathed on both sides with Ringer, displayed a mean short-circuit current of 94.1 +/- 10.4 muA/cm(2), a mean transepithelial potential difference of 14.8 +/- 1.9 mV (blood side positive), and a mean d.c. resistance of 169.0 +/- 14.0 Omega.cm(2) (mean +/- S.E. of mean; n = 20). Isotope flux studies across these short-circuited epithelia revealed a net Cl(-) blood side to freshwater side flux of 95.2 +/- 16.1 muA/cm(2) and no significant net flux of Na(+).7. The opercular epithelia of 200% seawater-adapted F. heteroclitus, when bathed on both sides with Ringer, displayed a mean short-circuit current of 33.5 +/- 8.5 muA/cm(2), a mean transepithelial potential difference of 10.5 +/- 2.5 mV (blood side positive), and a mean transepithelial d.c. resistance of 440.7 +/- 62.6 Omega.cm(2) (mean +/- S.E. of mean n = 18). Isotope flux studies across these short-circuited epithelia revealed a net Cl(-) blood side to seawater side flux of 96.2 +/- 51.5 muA/cm(2) and a net Na(+) blood side to seawater side flux of 65.3 +/- 28.6 muA/cm(2).

Adaptation, Physiological↗
PubMed1977

Renal handling of the polar DDT metabolite DDA (2,2-bis[p-chlorophenyl] acetic acid) by marine fish.

The renal handling of 2,2-bis(p-chlorophenyl) acetic acid (DDA) was examined in the isolated tubules of the winter flounder (Pseudopleuronectes americanus) in vitro in conjunction with clearance studies in the flounder and in the aglomerular goosefish (Lophius americanus). In vitro, both uptake studies and autoradiography showed extensive energy-dependent accumulation within the cytoplasm of tubular cells and the tubular lumen. The uptake was strongly inhibited by p-aminohippurate and chlorophenol red. A second component of uptake was insensitive to metabolic inhibitors or organic acids and represented tissue binding. In vivo, both species showed net secretion which was inhibited by probenecid. Comparison of DDT and DDA distribution and excretion emphasized the importance of the greater water solubility of DDA and of its secretory transport, since DDA was excreted at over 200 times the rate of DDT. Liver, kidney, and bile also showed elevated DDA tissue-to-plasma ratios. Thus, the organic acid system mediates the accumulation and excretion of DDA in these fish.

Animals↗
PubMed1976

Teleost chloride cell. I. Response of pupfish Cyprinodon variegatus gill Na,K-ATPase and chloride cell fine structure to various high salinity environments.

Certain euryhaline teleosts can tolerate media of very high salinity, i.e. greater than that of seawater itself. The osmotic gradient across the integument of these fish is very high and the key to their survival appears to be the enhanced ability of the gill to excrete excess NaCl. These fish provide an opportunity to study morphological and biochemical aspects of transepithelial salt secretion under conditions of vastly different transport rates. Since the cellular site of gill salt excretion is believed to be the "chloride cell" of the branchial epithelium and since the enzyme Na,K-ATPase has been implicated in salt transport in this and other secretory tissues, we have focused our attention on the differences in chloride cell structure and gill ATPase activity in the variegated pupfish Cyprinodon variegatus adapted to half-strength seawater (50% SW), seawater (100% SW), or double-stregth seawater (200% SW). The Na,K-ATPase activity in gill homogenates was 1.6 times greater in 100% SW. When 50% SW gills were compared to 100% SW gills, differences in chloride cell morphology were minimal. However, chloride cells from 200% SW displayed a marked hypertrophy and a striking increase in basal-lateral cell surface area. These results suggest that there are correlations among higher levels of osmotic stress, basal-lateral extensions of the cell surface, and the activity of the enzyme Na,K-ATPase.

Adenosine Triphosphatases↗
PubMed1976

Teleost chloride cell. II. Autoradiographic localization of gill Na,K-ATPase in killifish Fundulus heteroclitus adapted to low and high salinity environments.

The specific binding and inhibitory action of (3H)ouabain were employed to localize transport Na,K-ATPase in the euryhaline teleost gill, a NaCl-transporting osmoregulatory tissue in which both enzyme activity and transepithelial transport vary with environmental salinity. In killifish fully adapted to 10%, 100%, or 200% seawater, the gills were internally perfused and externally irrigated in situ. After suitable internal or external exposure to (3H)ouabain, individual gill arches were excised for Na,K-ATPase assay, measurement of radiolabel binding, or quantitative high-resolution autoradiography. Internal exposure to 50 muM ouabain resulted in essentially complete enzyme inhibition, and binding paralleled the increases in enzyme activity at higher salinities; in contrast, external exposure gave minimal and erratic results consistent with leakage of external ouabain into interstitial fluid. (3H)Ouabain autoradiographs demonstrated that, irrespective of exposure or salinity, most of the gill binding was associated with chloride cell. These cells increased in size and number with salinity and, at the subcellular level, the distribution pattern for bound ouabain was always identical to that for the amplified basal-lateral (tubular system) membrane. The combined physiologicmorphologic results constitute final direct proof that chloride cells are the primary site of gill Na,K-ATPase. More important, they provide convincing evidence for unexpected increases in basal-lateral enzyme at higher salinities and thus raise a fundamental objection to the long-postulated role of the Na pump in secretory NaCl transport.

Adenosine Triphosphatases↗
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↗