The localization and effects of mercury bound by the surviving frog skin

Abstract

The dependence of the spontaneous potential across the surviving frog skin in sodium-containing media on the active transport of sodium across the skin in the inward direction has been unequivocally demonstrated by a number of authors (see, e.g. Koefoed-Johnsen and Ussing, '60, for references). A number of substances inhibiting the active transport of sodium across the skin and thus bringing about a drop in the spontaneous potential across the skin toward zero are known; among these, mercuric chloride is noted for its pronounced inhibitory effect and greater inhibition when present in the medium bathing the outside of the skin than when added to the inside bathing solution. The effects of HgCL on the surviving frog skin were briefly summarized by Linderholm ('52): With 0.05 mM HgCl, on the outside of the skin the spontaneous potential across the skin decreased to zero within a few minutes and the direct-current resistance of the skin also decreased, usually after an initial increase. When applied to the inside, the effect was slower and a higher dose was required to obtain the same effect.The number and the anatomic localization of the electric potential drops which constitute the overall spontaneous potential across the skin decreasing to zero on application of inhibitors were investigated by means of micropuncture. Ottosen et al. ('53) using frog skin deprived of the tela subcutanea and the stratum compactum found a single potential drop at the point of puncture localized across the submicroscopic basement membrane which demarcates epidermis from the connective tissue of corium discovered by these authors with the aid of electron microscopy. Engbaek and Hoshiko ('57) performed micropuncture from the epidermal side of uninjured skin; they observed that the total potential difference across the skin consists of two potential drops, the first of which they assumed to be located inside of the epidermis, the other at the boundary between epidermis and corium. The composition of the total potential difference as being made up of two discrete potential drops was indicated by Scheer and Mumbach ('60); these authors localized the individual potential drops with the aid of a dye-marking technique in the region of stratum germinativum and tela subcutanea on the inner surface of the dermis. The fact that the potential difference across the skin represents the sum of two potential drops which may be envisaged as membrane potentials of two membranes separated by a conductive milieu justifies the early technique of Steinbach ('33). This technique makes it possible to measure the individual membrane potentials in frog skin between a calomel electrode connected through the injured edge of the skin with the internal milieu and either of two electrodes connected with solutions on both sides of the skin. It is the attempt of the present communication to contribute to our understanding of the effect of mercuric chloride on surviving frog skin with regard to the anatomic localization and to the basis of the chemical reaction involve...

Effects of Cd++ on short-circuit current across epithelial membranes

“…The inhibition of SCC produced by equimolar addition of cysteine and Cd § § to the apical Ringer's is similar to results obtained by Linderholm (1952) and Lodin et al (1963), who found 10-4M HgC12 alone to inhibit SCC when added to the apical surface of isolated Rana temporaria skin. Using the method of Steinbach (1933), Lodin et al (1963 found that this inhibition of SCC by Hg ++ treatment was associated with an increase in the resistance of the morphologically outer barrier of the epithelium with little or no effect on the inner barrier.…”

“…It would appear, then, that divalent metals can inhibit SCC by either reducing passive entry into epithelial cells, as Lodin et al (1963) observed for Hg + § or by directly inhibiting the active transport mechanism of the basal-lateral membranes, as observed with the bladder and large intestine. Furthermore, the presence of a carrier, such as cysteine or metallothionein, can modify the response at either site of action.…”

THE EFFECT OF METHIONINE ON THE REGIONAL AND INTRACELLULAR DISPOSITION OF [3H]‐METHIONINE SULPHOXIMINE IN RAT BRAIN1

“…These studies revealed : (a) that several methionine analogues and derivatives are equally effective, and (b) that a reversible breakdown of a part of cerebral polyribosomes to monoand dimeric ribosomes coincident with a transient stimulation of cerebral protein synthesis accompanies, and possibly mediates the seizure-protective action of methionine (SELLINGER and AZCURRA, 1970). LODIN and his co-workers (LODIN, FALTIN, PILNY and HARTMAN, 1968;LODIN, MULLER and FALTIN, 1968) have also recently described effects of MSO on nucleic acids and proteins in neural tissue. Previously the intracellular disposition of MSO in brain had been examined only cursorily ( LAMAR and SELLINGER, 1965;DE ROBERTIS et al, 1967), mainly because MSO of sufficiently high specific radioactivity was unavailable.…”