Mitochondria-rich cells of frog skin in transport mechanisms: morphological and kinetic studies on transepithelial excretion of methylene blue

Ehrenfeld, Jordi; Masoni, A.; Garcia-Romeu, F

doi:10.1152/ajplegacy.1976.231.1.120

Cited by 40 publications

(13 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the high density of MR cells encountered in the frog skins in the present work was sufficient to prevent localization in most instances. The effects of MR cells on the transport properties of the frog skin are generally ignored, although similar MR cell densities have been previously reported (Whitear, 1975;Ehrenfeld, Masoni & Garcia-Romeu, 1976).…”

Section: Discussionmentioning

confidence: 85%

Localization of chloride conductance to mitochondria-rich cells in frog skin epithelium

Foskett

Ussing

1986

J. Membrain Biol.

View full text Add to dashboard Cite

Cell volume determinations and electrophysiological measurements have been made in an attempt to determine if mitochondria-rich (MR) cells are localized pathways for conductive movements of Cl across frog skin epithelium. Determinations of cell volume with video microscope techniques during transepithelial passage of current showed that most MR cells swell when the tissue is voltage clamped to serosa-positive voltages. Voltage-induced cell swelling was eliminated when Cl was removed from the mucosal bath solution. Using a modified vibrating probe technique, it was possible to electrically localize a conductance specifically to some MR cells in some tissues. These data are evidence supporting the idea that MR cells are pathways for conductive movements of Cl through frog skin epithelium.

show abstract

Section: Discussionmentioning

confidence: 85%

Localization of chloride conductance to mitochondria-rich cells in frog skin epithelium

Foskett

Ussing

1986

J. Membrain Biol.

View full text Add to dashboard Cite

show abstract

“…Methylene blue is known to permeate biological membranes (Sass, Caruso & Axelrod, 1967;Ehrenfeld, Masoni & Garcia-Romeu, 1976), and the fact that MB inhibited I~ and "displaced" amiloride ( Fig. 6) with a relatively slow time course may indicate an internal site of action.…”

Section: Discussionmentioning

confidence: 99%

Effects of chemical group specific reagents on sodium entry and the amiloride binding site in frog skin: Evidence for separate sites

1980

View full text Add to dashboard Cite

Previously we have shown that the inhibition of active transport by amiloride is noncompetitive with sodium in Rana catesbeiana skin, suggesting that amiloride acts at a site separate from the sodium entry site (Benos, D.J., Mandel, L.J., Balaban, R.S. 1979, J. Gen Physiol. 73:307). In the present study, the effects of a number of sulfhydryl, amino, and carboxyl group selective reagents were studied on short-circuit current (Isc) as well as the efficacy of amiloride in bullfrog skin, to determine those functional ligands which may be involved with either of these processes.Addition of the sulfhydryl reagent PCMBS (1 raM) to the outside bathing medium produced biphasic effects, initially reversibly increasing Iso by an average 56% followed by a slower, irreversible decay to levels below baseline. In contrast, the addition of 0.1 m~ PCMB always resulted in a rapid, irreversible decrease in Isc. When a 40,000 tool wt dextran molecule was attached to PCMB, a stable, reversible increase in I~c was observed. These observations suggest that at least two populations of -SH groups are involved in Na translocation through the entry step. Amiloride was equally effective in inhibiting Is~ before and after treatment with PCMBS both during the stimulatory as well as the inhibitory phase. The sulfhydryl reducing agent DTT, and oxidizing agent DTNB had only minor influence on I~c and did not alter the effectiveness of amiloride.Similarly, the amino reagents, SITS and TNBS did not affect I~c. However, TNBS decreased the ability of amiloride to inhibit Na entry. These results suggest that an amino group may be involved in the interaction of amiloride and its site, without affecting Na entry.The carboxyl reagents EEDQ, TMO, and three separate carbodiimides were without effect on Is~ or amitoride inhibition, Methylene blue (MB), a molecule that interacts with both carboxyl and hydroxylspecific groups, inhibited Isc by 20% and decreased amiloride's ability to inhibit I~. These effects, however, are likely to occur from the cytoplasmic side as MB appears to enter into the cells.These results support the notion that amiloride and Na interact with the entry protein at different regions on the membrane.

show abstract

“…In some sections other epithelial cells could also be observed. Fig.2 shows a section which happens to, contain most of these epithelial structures: a gland excretion duct, a layer of light cells underneath the just shedding corneum, and a mitochondria-rich cell, identified by its characteristic pear shape [15].…”

Section: Methodsmentioning

confidence: 99%

Electron microprobe analysis of frog skin epithelium: Evidence for a syncytial sodium transport compartment

et al. 1978

View full text Add to dashboard Cite

For elucidation of the functional organization of frog skin epithelium with regard to transepithelial Na transport, electrolyte concentrations in individual epithelial cells were determined by electron microprobe analysis. The measurements were performed on 1-micron thick freeze-dried cryosections by an energy-dispersive X-ray detecting system. Quantification of the electrolyte concentrations was achieved by comparing the X-ray intensities obtained in the cells with those of an internal albumin standard. The granular, spiny, and germinal cells, which constitute the various layers of the epithelium, showed an identical behavior of their Na and K concentrations under all experimental conditions. In the control, both sides of the skin bathed in frog Ringer's solution, the mean cellular concentrations (in mmole/kg wet wt) were 9 for Na and 118 for K. Almost no change in the cellular Na occurred when the inside bathing solution was replaced by a Na-free isotonic Ringer's solution, whereas replacing the outside solution by distilled water resulted in a decrease of Na to almost zero in all layers. Inhibition of the transepithelial Na transport by ouabain (10(-4) M) produced in increase in Na to 109 and a decrease in K to 16. The effect of ouabain on the cellular Na and K concentrations was completely cancelled when the Na influx from the outside was prevented, either by removing Na or adding amiloride (10(-4) M). When, after the action of ouabain, Na was removed from the outside bathing solution, the Na and K concentration in all layers returned to control values. The latter effect could be abolished by amiloride. The other cell types of the epithelium showed under some experimental conditions a different behavior. In the cornified cells and the light cells, which occurred occasionally in the stratum granulosum, the electrolyte concentrations approximated those of the outer bathing medium under all experimental conditions. In the mitochondria-rich cells, the Na influx after ouabain could not be prevented by adding amiloride. In the gland cells, only a small change in the Na and K concentrations could be detected after ouabain. The results of the present study are consistent with a two-barrier concept of transepithelial Na transport. The Na transport compartment comprises all living epithelial layers. Therefore, with the exception of some epithelial cell types, the from skin epithelium can be regarded as a functional syncytium for Na.

show abstract

Mitochondria-rich cells of frog skin in transport mechanisms: morphological and kinetic studies on transepithelial excretion of methylene blue

Cited by 40 publications

References 0 publications

Localization of chloride conductance to mitochondria-rich cells in frog skin epithelium

Localization of chloride conductance to mitochondria-rich cells in frog skin epithelium

Effects of chemical group specific reagents on sodium entry and the amiloride binding site in frog skin: Evidence for separate sites

Electron microprobe analysis of frog skin epithelium: Evidence for a syncytial sodium transport compartment

Contact Info

Product

Resources

About